Saltriovenator, which demonstrates an early stage in the theropod hand, suggests that the small fourth finger of early theropods disappeared as theropods evolved, while their first three fingers gave rise to bird wings.
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Unlike birds, most theropods had two egg tubes, not one.
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Theropods were bipedal dinosaurs and most, but not all, were carnivorous.
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After all, birds evolved from tiny, meat-eating dinosaurs called theropods.
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People who study theropods, say, oh, tyrannosaurs get all the attention.
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The theropods were only about three feet at the hip, she said.
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Theropods have long been considered an offshoot from the lizard-hipped Saurischia.
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Now scientists think that theropods like T. rex probably even had feathers.
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All three theropods had beaks but with vestigial, or functionless, tooth sockets.
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The carcharodontosaurs differed from some of the more heavily built theropods like Tyrannosaurus.
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The so-called reptile-hipped Saurischia covered theropods including birds and the sauropods.
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The lizard-hipped ones include theropods like the T. rex and sauropodomorphs like Brontosaurus.
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These fearsome, mid-sized theropods featured large claws and air-filled bird-like bones.
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Theropods engaged in scrape ceremony display activity, based on trace fossil evidence from Colorado.
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The first, called Ornithoscelida, joins the theropods with all the current members of Ornithischia.
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Oh, and also gigantic sauropods and carnivorous two-legged theropods, as this latest discovery affirms.
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It was not bird-hipped Ornithischia that gave rise to birds, but lizard-hipped theropods.
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Instead, the animal represents a kind of intermediary species somewhere between herbivorous dinosaurs and carnivorous theropods.
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"No matter whether you were big or small, theropods were making your life miserable," he said.
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They also have a bit of a reputation of being one of the least exciting theropods.
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Meat-eating dinosaurs, including Saltriovenator, belong to a group of two-legged dinosaurs known as theropods.
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Unlike better known theropods like velociraptors, "this guy was not a traditional meat eater," Dr. Brusatte said.
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The Saurischian branch includes both sauropods like the herbivorous diplodocus, and theropods like the meat-eating tyrannosaurs.
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He spotted the tracks of the four small theropods, all headed in the same direction, walking slowly.
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Gizmodo: All terrestrial dinosaurs, from the turkey-sized theropods through to long necked, 15-ton sauropods, laid eggs.
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The rest of the Ornithischia and the theropods, meanwhile, are joined as a newly named group, the Ornithoscelida.
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If theropods did something other than scrape the world up, we don't yet have physical evidence for it.
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"But obviously there was some adaptive advantage because we see it multiple times in different lineages of theropods."
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On an evolutionary scale this transition happened until theropods developed mouths that resembled the bird beaks seen today.
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Mixed with the herbivores' tracks were a few clawed impressions left behind by two-legged meat-eaters known as theropods.
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Two-legged theropods and big-bodied sauropods, among other groups, walked this patch of Earth around 130 million years ago.
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This runs in contrast to a number of other dinosaurs, including theropods and ornithischians, for whom parental care was paramount.
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The new dinosaur belonged to a different type of theropods called the allosaurs, which usually had strong, proportionally sized arms.
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The current Saurischia group would lose the theropods but add a strange, primitive group of two-legged carnivores called herrerasaurids.
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The researchers think they were made by theropods, a big group of bipedal and carnivorous dinosaurs that included tyrannosaurs and raptors.
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For this reason, some at the site speculated that the tracks might be a game trail: theropods stalking their sauropod prey.
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Essentially they have found that the Ornithischian dinosaurs have many similarities with the theropods and so probably shared a common ancestor.
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Gualicho and other carnivorous dinosaurs like Tyrannosaurus rex are part of a group called theropods that included Earth's largest-ever land predators.
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The new tree puts the theropods — which were originally considered lizard-hipped — together with the bird-hipped dinosaurs into a combined group.
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IN RECENT years it has become clear that many, if not all, dinosaurs belonging to a group called the theropods had feathers.
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So Bishop and his colleagues turned to the next best thing: birds, the only surviving descendants of two-legged dinos called theropods.
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One of the biggest shake-ups involves theropods, a group that includes the T. Rex and other ancestors of modern day birds.
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Instead, they separate the two great subgroups of Saurischia, the sauropods (Brontosaurus, Diplodocus, etc) and the theropods (Tyrannosaurus, Allosaurus, etc) and reassign them.
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Likewise, smaller theropods referenced in the study, such as the Maniraptoriformes clade from which birds evolved, were less likely to have cranial ornamentation.
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The tracks laid by the theropods were made by several medium-to-large specimens, about five to six meters long and weighing a ton.
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Wiemann and Norell both hypothesized that the emergence of egg color stemmed from theropods no longer laying their eggs in underground or covered nests.
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The impressions were all found in the same sediment layer, which indicated to the team that the sauropods and theropods shared the stomping ground.
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We know they were sauropods (a family long-necked herbivores, including the likes of Brontosaurus) and theropods (carnivores and older cousins of Tyrannosaurus Rex).
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Famous lizard-hipped Saurischians include Tyrannosaurus rex, (and many of the other bipedal carnivore dinosaurs, called theropods), whereas Ornithischians included dinosaurs such as Stegosaurus.
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Previously, they've been able to trace the early evolution of armored dinosaurs, long-necked sauropods and the cousins of Tyrannosaurus rex-like carnivorous theropods.
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Three-toed footprints with sharp claws appear to have been made by a jeep-sized two-legged carnivorous dinosaur from a group called theropods.
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Scientists believe that during their evolution, theropods lifted their forelimbs off the ground and modified them for catching prey, and bird wings evolved from there.
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Like modern birds, advanced theropods had long, S-shaped brains with a relatively large cerebellum and optic lobe, and a small area devoted to smell.
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Dinosaur expert Thomas Holtz Jr. of the University of Maryland, who didn't participate in the work, said it's reasonable to think that theropods created the grooves.
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The only comparable animals alive today with teeth that stick out are crocodiles, which are aquatic, he noted, unlike virtually all theropods, Spinosaurus being an exception.
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This distinctly bird-like creature belonged to a group of dinosaurs known as the Yaniliao theropods, a suborder known for their hollow bones and three-toed limbs.
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I really loved collaborating with the authors to get things right on this painting, depicting the late Cretaceous diversity in small theropods in the Hell Creek Formation.
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New research suggests that theropods -- those "beast-footed" terrestrial carnivores -- had lips and gums that covered most of their teeth, challenging toothy ideas of what they looked like.
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Along with the tyrannosaurs, and a second dinosaur group known as the abelisaurs, Gualicho shinyae is one of the few theropods with tiny arms that paleontologists have found.
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As for which dinosaurs made Borealopelta their lunch, Brown suspects two-legged theropods like Acrocanthosaurus, or a similar large Carcharodontosauroid—a bipedal beast even larger than Tyrannosaurus and Spinosaurus.
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Scotty is now officially the largest and most aged T. rex ever discovered, and the most gigantic of any of the known two-legged carnivorous dinosaurs known as theropods.
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We do know that some dinosaurs, particularly the very bird-like feathered theropods like Oviraptor and Troodon, were great parents that guarded their nests and even sat on their eggs.
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Such behavior is seen nowadays in some birds, and the discovery suggests that two-legged, meat-eating dinosaurs called theropods did it about 100 million years ago, the researchers said.
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Most scientists now believe that birds are theropods, dinosaurs of a group that included tyrannosaurus and spinosaurus, but that birds were on their own evolutionary branch from a common ancestor.
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As it happens, Thomas Huxley, the celebrated 19th century champion of Darwin's theory of evolution, also thought Ornithischia and theropods belonged together in the same group, which he called Ornithoscelida.
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This technology allowed scientists to see the outline of toes and claws, and tentatively assign the footprints to long-necked sauropods and theropods, dinosaurs related to the Brontosaurus and Tyrannosaurus rex.
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Some will say feathers originated independently three or four times—pterosaurs, ornithischians, theropods—we say: Show us evidence that the pterosaur feathers are actually different in any way from these others.
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For instance, Gates and his co-authors suggested that large ornamented theropods may have inhabited unforested, open habitats where their attention-grabbing headpieces would be most conspicuous to mates and rivals.
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There are also tracks of four theropods — relatives of the Tyrannosaurus rex that lived tens of millions of years later, but these were smaller, roughly the size of a large raven.
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It turns out that the long-necked sauropods weren't alone; they shared the region with some carnivorous theropods, distant cousins of the T-rex, which wouldn't make its dreaded appearance until much later.
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Every couple of minutes someone uncovered new tracks made by theropods (bipedal carnivores whose prints show three talonlike toes) or sauropods (plant eaters that walked on all fours, leaving circular prints like potholes).
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"Gualicho is kind of a mosaic dinosaur, it has features that you normally see in different kinds of theropods," noted study co-author Peter Makovicky, who works out of the Field Museum in Chicago.
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"That changes our picture of what is within the range of possibility for these large animals and expands our understanding of the biology of large theropods at that extreme end of the size range," Carr told Gizmodo.
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Moreover, ornamented theropods that weighed over 1,000 kilograms (2,203 pounds) experienced accelerated giantism, meaning they grew larger at about 20 times the rate of unornamented theropod species, suggesting there is a link between extravagant headgear and theropod size.
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It's not literally the "missing link" that divides ornithischians from theropods (two major dinosaur groups that lived from the early Jurassic to the Late Cretaceous), but its discovery shows how dinosaurs were changing during this important time in evolution.
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An open nest meant that eggs that blended in had a better shot of surviving than stark white eggs did—or in other cases, perhaps theropods needed to recognize their own eggs in case another animal sneakily laid an egg in the nest.
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The study, which was published Wednesday in the journal Nature, now calls for theropods such as T. rex to be grouped with the Ornithischians, and for sauropods (including Brontosaurus, Apatosaurus, and Brachiosaurus) to be included with a group of early dinosaurs called Herrerasauridae.
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The carcharodontosaurs are part of a larger dinosaur assemblage called theropods that encompasses all the carnivorous dinosaurs including the likes of Tyrannosaurus rex, which lived in North America at the end of the age of dinosaurs some 66 million years ago, as well as birds.
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This analysis projected the origin of feathers back to the common ancestor of pterosaurs and dinosaurs, namely ornithischians (plant-eating dinosaurs) and theropods (two-legged carnivorous dinosaurs and the ancestors of all birds)—a branching that occurred during the early Triassic, around 250 million years ago.
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"It begins to tell us a little bit about the story of how and why animals like T-rex and other theropods reduce their forearms," said Peter Makovicky, a paleontologist with the Field Museum in Chicago, and an author of a paper published Wednesday in the journal PLOS One.
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A compact, easily navigated exhibition, it presents the visual evidence with freshly exhumed fossils, interactive displays and reconstructed theropods — bipedal, nonavian relatives of the 13,000 or more bird species alive today — that prove, if nothing else, that evolution has made wonderful cosmetic improvements over the past 150 million years.
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For their most recent paper, he and his colleagues examined more dinosaur jaw fossils and found two other theropods that underwent transitions similar to Limusaurus: an early Cretaceous bird called Sapeornis, which resembled modern birds, and a small caenagnathid oviraptorosaur, which resembled a velociraptor but with a beak.
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Before the discovery of Halszkaraptor, the entire idea of small, waterbird-like theropods hunting down fish was some mix of inconceivable or speculative fiction (Halszkaraptor is eerily similar to the pouch in Dougal Dixon's The New Dinosaurs, which imagines an alternate timeline in which the non-avian dinosaurs never went extinct).
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Far from the toothy, snarling monster we've come to know and love, Tyrannosaurus rex—and other theropods like it—might have sported a pair of lips, argues Robert Reisz, a paleontologist at the University of Toronto's Mississauga campus, who's presenting his theory on Friday at the annual Canadian Society of Vertebrate Paleontology meeting.
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Now at the University of Edinburgh, and not content to focus on just one aspect of dinosaurs, Brusatte studies the origin and early evolution of dinosaurs, the anatomy and genealogy of carnivorous theropods, such as T. rex and its relatives, the evolution of birds, and the mass extinction of dinosaurs at the end of the Cretaceous.
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They also found at least 20 individual coelophysoid theropods (bipedal, mostly meat-eating dinosaurs), the teeth of a much larger theropod, a drepanosaurid (a creature with a head like a bird, arms like a mole and a claw at the end of its tail) and two types of sphenodontids (which looks like the modern tuatara of New Zealand ).
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This feature was common in theropods of its time, but would disappear in later theropods.
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Preserved pathologies are less common among small theropods. This may be due to the tendency of larger animals to leave better preserved and more complete remains. Fractures, specifically, are less than a fifth as common in small theropods as large ones. Molnar has tentatively speculated that size may be a factor in determining which theropods suffered fractures.
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Abelisauroid theropods Skorpiovenator and Ilokelesia also lived in the region.
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Notes on Early Mesozoic Theropods (First ed.). Lulu press. pp. 9-24.
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Dinosaur Facts and Figures: The Theropods and Other Dinosauriformes. Princeton University Press.
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Coelurosaurian theropods are the notable exception to the pattern of body size increases.
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Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and is the only group of theropods that survived the Triassic–Jurassic extinction event. All neotheropods became extinct during the early Jurassic period except for Averostra.
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Other large carnivorous theropods included Giganotosaurus, Carcharodontosaurus and Tyrannosaurus. Therizinosaurus and Deinocheirus were among the tallest of the theropods. The largest ornithischian dinosaur was probably the hadrosaurid Shantungosaurus giganteus which measured . The largest individuals may have weighed as much as .
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Originally, Lydekker found that Sarcolestes represented a theropod. He cited lack of a predentary as excluding the taxon from ornithopods, and tooth morphology as excluding it from sauropods. Within theropods, it was found to be sufficiently different from one main groups of theropods including Coelurus, Calamosaurus, and Compsognathus, and the megalosaurids including Megalosaurus. Thus, Lydekker placed it in Thecodontosauridae, a group of theropods (now placed in sauropodomorpha) including Thecodontosaurus.
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The SharpClaw tribe are villainous humanoid theropods. Andross also appears as the final boss.
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Like theropod teeth, the teeth of Dryadissector are recurved, laterally compressed, and serrated. However, their lizard affinities are made evident by serrations that are smaller and more numerous than those of theropods, as well as a bulge on the inner surface of the base of each tooth that is characteristic of varanoids. In most Late Cretaceous fossil assemblages where varanoids and theropods coexist (e.g. the Foremost and Oldman formations in Alberta, where the varanoid Palaeosaniwa is found alongside theropods like Saurornitholestes), varanoids are a rare component of the fauna and their teeth are greatly outnumbered by those of theropods.
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Oligokyphus lived beneath the feet of dinosaurs, such as the theropods Dilophosaurus, KayentavenatorGay, R. 2010. Kayentavenator elysiae, a new tetanuran from the early Jurassic of Arizona. Pages 27–43 in Gay, R. Notes on early Mesozoic theropods. Lulu Press (on-demand online press).
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Gasosarurus lived during the mid-Jurassic period (Bathonian and/ or Callovian stages), around 164 million years ago. It coexisted with other mid-range theropods such as Chuandongocoelurus and Kaijiangosaurus, two other dinosaurs found from the Lower Shaximiao Formation. These three taxa pertain to medium to large bodied theropods and are known from associated prostcranial skeletons. China, boasts the highest taxic diversity of Middle Jurassic theropods of all body sizes from anywhere in the world.
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Sarahsaurus shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus, Kayentavenator,Gay, R. 2010. Kayentavenator elysiae, a new tetanuran from the early Jurassic of Arizona. Pages 27–43 in Gay, R. Notes on early Mesozoic theropods. Lulu Press (on-demand online press).
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Prismatoolithidae is an oofamily of fossil eggs. They may have been laid by ornithopods or theropods.
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The interrelationships and evolution of basal theropods (Dinosauria, Saurischia). Ph.D. dissertation, Univ. Bristol [U.K.]. 440 pp.
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In 1999, Xing Xu and colleagues described Beipiaosaurus, a small, basal therizinosaur from China, which confirmed the group belonged among the coelurosaurian theropods, and that similarities with prosauropods had evolved independently. They published the first cladogram showing the evolutionary relationships of Therizinosauria and demonstrated Beipiaosaurus retained features of more basal theropods and coelurosaurs, which linked them with therizinosaurs. The preservation of feather-like structures in Beipiaosaurus also suggested this feature was more widely distributed among theropods than previously thought.
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Rauhut, O. W., and Hungerbühler, A. (2000). "A review of European Triassic theropods." Gaia, 15: 75-88.
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Romer considered Gracilisuchus to be, "quite clear[ly]", a relative of the Scottish Ornithosuchus, owing to similarities in skull structure and other skeletal features. When Alick Walker described Ornithosuchus in 1964, he suggested that Teratosaurus and Sinosaurus were its closest relatives, collectively forming the family Ornithosuchidae. He further suggested that they were theropod dinosaurs. At this time, theropods were divided into two groups following Romer's 1956 classification: the Coelurosauria (long-necked, small-headed theropods) and Carnosauria (short- necked, large-headed theropods).
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Under this modern definition, many small theropods are not classified as coelurosaurs at all and some large theropods, such as the tyrannosaurids, were actually more advanced than allosaurs and therefore were reclassified as giant coelurosaurs. Even more drastically, the segnosaurs, once not even regarded as theropods, have turned out to be non-carnivorous coelurosaurs related to Therizinosaurus. Senter (2007) listed 59 different published phylogenies since 1984. Those since 2005 have followed almost the same pattern, and differ significantly from many older phylogenies.
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Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.
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Rauhut, 2000. The interrelationships and evolution of basal theropods (Dinosauria, Saurischia). PhD thesis, University of Bristol. 440 pp.
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Restoration of two Majungasaurus chasing Rapetosaurus Scientists have suggested that the unique skull shape of Majungasaurus and other abelisaurids indicate different predatory habits than other theropods. Whereas most theropods were characterized by long, low skulls of narrow width, abelisaurid skulls were taller and wider, and often shorter in length as well. The narrow skulls of other theropods were well equipped to withstand the vertical stress of a powerful bite, but not as good at withstanding torsion (twisting). In comparison to modern mammalian predators, most theropods may have used a strategy similar in some ways to that of long- and narrow-snouted canids, with the delivery of many bites weakening the prey animal.
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Theropoda ( from Greek "wild beast" and "foot"), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three-toed limbs. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.
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Non- avian theropods were first recognized as bipedal during the 19th century, before their relationship to birds was widely accepted. During this period, theropods such as carnosaurs and tyrannosaurids were thought to have walked with vertical femurs and spines in an upright, nearly erect posture, using their long, muscular tails as additional support in a kangaroo-like tripodal stance. Beginning in the 1970s, biomechanical studies of extinct giant theropods cast doubt on this interpretation. Studies of limb bone articulation and the relative absence of trackway evidence for tail dragging suggested that, when walking, the giant, long-tailed theropods would have adopted a more horizontal posture with the tail held parallel to the ground.
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The East Berlin Formation is an Early Jurassic geological formation in New England. Dinosaur footprints and trackways are abundant in this formation. These tracks include Eubrontes (belonging to medium sized-theropods like Dilophosaurus), Anchisauripus (belonging to small theropods like Coelophysis), and Anomoepus (belonging to indeterminate small ornithischians).Weishampel, et al. (2004).
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Such spaces, which are also found in modern theropods (that is, the birds), are interpreted as having held air sacs used in respiration. The rib cage was broad, giving it a barrel chest, especially in comparison to less derived theropods like Ceratosaurus.Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 277.
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The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV),See Origin of birds/Digit homology. with sharp claws. Some basal theropods (e.g.
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Stegosaurs were apparently rare (e.g. Regnosaurus northamptoni). Theropods like Concavenator and Baryonyx may have existed alongside it as well.
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Footprints discovered in the formation include those of theropods, hadrosaurs, ceratopsians, ankylosaurs, pterosaurs and birds, notably the Magnoavipes denaliensis.
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Restoration of Spinosaurus swimming among contemporaneous aquatic animals A 2010 publication by Romain Amiot and colleagues found that oxygen isotope ratios of spinosaurid bones indicates semiaquatic lifestyles. Isotope ratios from teeth from Baryonyx, Irritator, Siamosaurus, and Spinosaurus were compared with isotopic compositions from contemporaneous theropods, turtles, and crocodilians. The study found that, among theropods, spinosaurid isotope ratios were closer to those of turtles and crocodilians. Siamosaurus specimens tended to have the largest difference from the ratios of other theropods, and Spinosaurus tended to have the least difference.
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The Therrien and Henderson study has been criticized for the choice of theropods used for comparison (e.g., most of the theropods used to set the initial equations were tyrannosaurids and carnosaurs, which have a different build than spinosaurids), and for the assumption that the Spinosaurus skull could be as little as in length.
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A fossil snout referred to Spinosaurus was discovered with a vertebra from the sclerorhynchid Onchopristis embedded in it. In the Sao Khua Formation of Thailand, isolated tooth crowns from Siamosaurus have been found in association with sauropod remains, indicating possible predation or scavenging. A 2018 study by Auguste Hassler and colleagues of calcium isotopes in the teeth of North African theropods found that spinosaurids had a mixed diet of fish and herbivorous dinosaurs, whereas the other theropods examined (abelisaurids and carcharodontosaurids) mainly fed on herbivorous dinosaurs. This might indicate ecological partitioning between these theropods.
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Specimen of the troodontid Jinfengopteryx elegans, with seeds preserved in the stomach region Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to the avian theropods (birds). However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages. All early finds of theropod fossils showed them to be primarily carnivorous.
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The herrerasaurs were characterised by a mosaic of primitive and advanced features. Some paleontologists have in the past considered the herrerasaurians to be members of Theropoda, while other theorized the group to be basal saurischians, and may even have evolved prior to the saurischian- ornithischian split. Cladistic analysis following the discovery of Tawa, another Triassic dinosaur, suggests the herrerasaurs likely were early theropods.. The earliest and most primitive unambiguous theropods (or alternatively, "Eutheropoda"—'True Theropods') are the Coelophysoidea. The Coelophysoidea were a group of widely distributed, lightly built and potentially gregarious animals.
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Some sauropods also evolved tooth batteries, best exemplified by the rebbachisaurid Nigersaurus. The early forms Herrerasaurus (large), Eoraptor (small) and a Plateosaurus skull There were three general dinosaur faunas in the Late Cretaceous. In the northern continents of North America and Asia, the major theropods were tyrannosaurids and various types of smaller maniraptoran theropods, with a predominantly ornithischian herbivore assemblage of hadrosaurids, ceratopsians, ankylosaurids, and pachycephalosaurians. In the southern continents that had made up the now-splitting Gondwana, abelisaurids were the common theropods, and titanosaurian sauropods the common herbivores.
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While he conceded they had similarities with ornithischians and theropods, he proposed these features had evolved independently. In a 1989 conference abstract about sauropodomorph inter-relationships, Paul Sereno also considered segnosaurs to be prosauropods, based on skull features. Reconstructed skeleton of Alxasaurus from China in Royal Tyrrell Museum, the completeness of which confirmed therizinosaurs as theropods In a 1990 review article, Barsbold and Teresa Maryańska found Segnosauria to be a rare and aberrant group of saurischians in an unresolved position among sauropodomorphs and theropods, and probably closer to the former.
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Naish, D. 1999. Fox, Owen and the small Wealden theropods Calamospondylus and Aristosuchus. Journal of Vertebrate Paleontology, 19 (Suppl. 3), 66.
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"On the presence of furculae in some non-maniraptoran theropods". Journal of Vertebrate Paleontology. 16 (3): 573–577. doi:10.1080/02724634.1996.
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They are similar to other theropods such as Megalosaurus, Sinraptor, and Ceratosaurus in being 1.5 times the height of the centrum.
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Although only the first phalanges are preserved, the second phalanges would have been mobile, as indicated by the well-developed articular surfaces, and the digits would likely have allowed a similar degree of motion as in other basal theropods. As in other theropods other than abelisaurids, digit I would have been slightly turned in when flexed.
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Nonetheless, the dinosaur mesothermy hypothesis requires further support to be confirmed. Fossil oxygen isotopes, which can reveal an organism's body temperature, should be particularly informative. Recently, a study of theropod and sauropod isotopes offered some support for dinosaur mesothermy. Feathered theropods are probably the best candidates for dinosaur endothermy, yet the examined theropods had relatively low body temperatures .
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Life restoration Based on the proportions of related theropods, Daemonosaurus is estimated to have been around 1.5 m (5 feet) long. Other estimates suggest that Daemonosaurus was at most long and weighed . The skull of Daemonosaurus differs considerably from all other Triassic theropods. The snout is short and bears large premaxillary and maxillary teeth in the upper jaw.
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Thus insulation, and the elevated metabolic rate behind evolving them, may have been limited to the theropods, or even just a subset of theropods. Lack of feathers or other sort of insulation does not indicate ectothermy or low metabolisms, as observed in the relative hairlessness of mammalian megafauna, pigs, human children and the hairless bat being compatible with endothermy.
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Fossil of an Anchiornis, showing large preserved feather imprints Mesozoic theropods were also very diverse in terms of skin texture and covering. Feathers or feather-like structures are attested in most lineages of theropods. (See feathered dinosaur). However, outside the coelurosaurs, feathers may have been confined to the young, smaller species, or limited parts of the animal.
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There are a few theories for the reasons feathers evolved in the first place, if not for flight. The first is that they served a purpose as insulation. Theropods have been found covering their nests with their forelimbs, thought to be sheltering their young. Feathers known to be found on theropods would have played an important role for insulation.
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A 2020 study on paravian flight capacities demonstrates that Jinfengopteryx matches closely with other flying non-avian theropods like Microraptor and Rahonavis.
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Abelodon lived alongside various archosaurs in the Koum Formation, such as ornithopod dinosaurs like Ouranosaurus, theropods like Spinosaurus, and crocodilians like Araripesuchus.
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He proposed that if Dilophosaurus was more derived than the Coelophysoidea, the features it shared with this group may have been inherited from basal (or "primitive") theropods, indicating that theropods may have passed through a "coelophysoid stage" in their early evolution. In 2007, American paleontologist Nathan D. Smith and colleagues found the crested theropod Cryolophosaurus to be the sister species of Dilophosaurus, and grouped them with Dracovenator and Sinosaurus. This clade was more derived than the Coelophysoidea, but more basal than the Ceratosauria, thereby placing basal theropods in a ladder-like arrangement. In 2012, Carrano and colleagues found that the group of crested theropods proposed by Smith and colleagues was based on features that relate to the presence of such crests, but that the features of the rest of the skeleton were less consistent.
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"Saurischian dinosaurs: theropods." in Martill, D.M. and Naish, D. (eds). Dinosaurs of the Isle of Wight. The Palaeontological Association, Field Guides to Fossils.
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Following the publication of Madsen's influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi- technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to Allosaurus included Indosaurus, Piatnitzkysaurus, Piveteausaurus, Yangchuanosaurus, Acrocanthosaurus, Chilantaisaurus, Compsosuchus, Stokesosaurus, and Szechuanosaurus. Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus, are members of closely related families.
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Most Middle Jurassic theropods from china are 'medium-sized', as are the majority of Middle Jurassic theropods globally. These similar dinosaurs show an intriguing combination of derived tetanuran synapomorphies and primitive features shared with non-tetanurans, which suggest they occupy a basal position within Tetanurae. Understanding the anatomy of Chinese Jurassic taxa may reveal further details of primitive tetanuran anatomy and help resolve the early evolution of this successful theropod clade. Future exploration of the Chinese Middle Jurassic theropod record may bring new insights into the diversification of Tetanurae, the origin of larger body sizes among more derived theropods, and Middle Jurassic paleobiogeography.
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Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. For example, a Compsognathus longipes fossil was found with a lizard in its stomach, and a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi (a type of ornithischian dinosaur). The first confirmed non-carnivorous fossil theropods found were the therizinosaurs, originally known as segnosaurs. First thought to be prosauropods, these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods.
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Posterior to this year, Clark and colleagues redescribed the holotype skull of Erlikosaurus and found more theropod traits than when first described. They concluded that therizinosaurs were more likely to be classified as maniraptoran theropods. Therizinosauria itself, was erected in 1997 by Rusell in order to contain all of these theropods. This new infraorder was composed of Therizinosauroidea and the more advanced Therizinosauridae.
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With the discovery and description of the feathered Beipiaosaurus, therizinosaurs were utterly recognized as theropods, and started to be reconstructed in an accurate, bipedal posture. Consequently, therizinosaurs are now classified as theropods, within the Coelurosauria. Lindsay Zanno was one of the first authors to examine in detail the relationships and affinites of therizinosaurs. Her work has been useful in many phylogenetic analyses.
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Megaraptora is a clade of carnivorous theropod dinosaurs with controversial relations to other theropods. Its derived members, the Megaraptoridae are noted for their elongated hand claws and proportionally large arms, which are usually reduced in size in other large theropods. Megaraptorans are incompletely known, and no complete megaraptoran skeleton has been found. However, they still possessed a number of unique features.
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In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone. He found pathological features in 21 genera from 10 families. Pathologies were found in theropods of all body size although they were less common in fossils of small theropods, although this may be an artifact of preservation. They are very widely represented throughout the different parts of theropod anatomy.
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Dinosaurs that have been given as evidence of biogeography include abelisaurid theropods from South America and possibly elsewhere on Gondwana. Relationships between dinosaurs show abundant evidence of dispersal from one region of the globe to another. Tetanuran theropods travelled widely through western North America, Asia, South America, Africa and Antarctica. Pachycephalosaurs and ceratopsians show clear evidence of multiple bidirectional dispersion events across Beringia.
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Unlike other theropods in their study of specimens found associated with eggs or nests, it had finished growing at the time of its death.
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Tykoski, R. S. 2005. Anatomy, ontogeny, and phylogeny of coelophysoid theropods. Unpublished PhD thesis, University of Texas at Austin, 552 pp.Kammerer, C. F. 2010.
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The interpretation of dinosaurs as gregarious has also extended to depicting carnivorous theropods as pack hunters working together to bring down large prey. However, this lifestyle is uncommon among modern birds, crocodiles, and other reptiles, and the taphonomic evidence suggesting mammal- like pack hunting in such theropods as Deinonychus and Allosaurus can also be interpreted as the results of fatal disputes between feeding animals, as is seen in many modern diapsid predators. Centrosaurus apertus engaged in intra- specific combat The crests and frills of some dinosaurs, like the marginocephalians, theropods and lambeosaurines, may have been too fragile to be used for active defense, and so they were likely used for sexual or aggressive displays, though little is known about dinosaur mating and territorialism. Head wounds from bites suggest that theropods, at least, engaged in active aggressive confrontations.
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Among smaller to medium-sized species such as dromaeosaurids, longer legs appear to be an adaptation for faster running, in line with previous results by other researchers. But for theropods weighing over , top running speed is limited by body size, so longer legs instead were found to have correlated with low-energy walking. The results further indicate that smaller theropods evolved long legs as a means to both aid in hunting and escape from larger predators while larger theropods that evolved long legs did so to reduce the energy costs and increase foraging efficiency, as they were freed from the demands of predation pressure due to their role as apex predators. Compared to more basal groups of theropods in the study, tyrannosaurs like Tyrannosaurus itself showed a marked increase in foraging efficiency due to reduced energy expenditures during hunting or scavenging.
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Hadrosaurs from these localities include Tanius, Tsintaosaurus, Laiyangosaurus and Shantungosaurus. Other taxa uncovered include the theropods Chingkankousaurus and cf. Szechuanosaurus campi, and the testudine Glyptops.
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Tanystrosuchus is considered to be a nomen dubium for that reason.Rauhut, O.M.W. & Hungerbühler, A. (2000) "A review of European Triassic theropods." Gaia, 15: 75-88.
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Zelenitsky, D. K. And Therrien, F. (2008), "Phylogenetic Analysis Of Reproductive Traits Of Maniraptoran Theropods And Its Implications For Egg Parataxonomy." Palaeontology, 51: 807–816.
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Juvenile Dracovenator regenti snout on display at the Royal Ontario Museum Yates (2005) assigned Dracovenator to the clade Neotheropoda.A. M. Yates. 2005. A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods. Palaeontologia Africana 41:105-122 The first cladistic analysis found that this genus formed a clade with the basal theropods Dilophosaurus and Zupaysaurus.
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Carnosauria has traditionally been used as a dumping ground for all large theropods. Even non-dinosaurs, such as the rauisuchian Teratosaurus, were once considered carnosaurs. However, analysis in the 1980s and 1990s revealed that other than size, the group shared very few characteristics, making it polyphyletic. Most former carnosaurs (such as the megalosaurids, the spinosaurids, and the ceratosaurs) were reclassified as more primitive theropods.
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Overoraptor was found in the Huincul Formation, a geological unit that has been extensively studied in recent years. Overoraptor lived alongside theropods such as the noasaurid Huinculsaurus, abelisaurids like Skorpiovenator, Ilokelesia and Tralkasaurus, carcharodontosaurids like Mapusaurus and indeterminate theropods like Gualicho and Aoniraptor. Sauropods were represented by the rebbachisaurids Cathartesaura and Limaysaurus, the titanosaurs Argentinosaurus and Choconsaurus, and some unnamed species. Ornithischians were represented by unnamed iguanodonts.
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Restoration showing scaly skin with sparse feathering, and lipped jaws The largest known T. rex skull is in length. Large fenestrae (openings) in the skull reduced weight, as in all carnivorous theropods. In other respects Tyrannosaurus's skull was significantly different from those of large non-tyrannosaurid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.
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Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with Ceratosaurus than with birds. Ceratosaurs are believed to have diverged from the rest of Theropoda by the early Jurassic, however, the oldest confirmed discovered specimens date to the Late Jurassic. According to the majority of the latest research, Ceratosauria includes the Late Jurassic to Late Cretaceous theropods Ceratosaurus, Elaphrosaurus, and Abelisaurus, found primarily (though not exclusively) in the Southern Hemisphere. Originally, Ceratosauria included the above dinosaurs plus the Late Triassic to Early Jurassic Coelophysoidea and Dilophosauridae, implying a much earlier divergence of ceratosaurs from other theropods.
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While exhibiting many typical therizinosaur features in overall body shape and in the teeth, the skeleton of Alxasaurus also shows several features present in more typical theropods, and the discovery of this animal provided significant evidence that therizinosaurs were aberrant theropods. Specifically, the semilunate carpal bone of the wrist is found only in maniraptoran theropods, which also include oviraptorosaurs, dromaeosaurs, troodontids, and birds. Even more basal therizinosaurs such as the feathered Beipiaosaurus and primitive Falcarius have since been discovered with more theropod features and have helped to solidify this arrangement. Alxasaurus is now thought to occupy a position between the early Beipiaosaurus and later therizinosaurids such as Erlikosaurus, Segnosaurus, or Therizinosaurus.
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Each egg measured long by wide. The presence of two developed eggs suggests that Sinosauropteryx had dual oviducts and laid eggs in pairs, like other theropods.
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Of the theropods found at La Cantalera (so far represented only by teeth), only aff. Paronychodon sp. and an indeterminate maniraptoran are possible parents of Trigonoolithus.
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As a consequence, the ability to make tight turns would have been diminished, because the hip and tail had to be turned simultaneously, unlike in other theropods.
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Some scientists have noted that the tibia closely resembles those of Liliensternus and Dilophosaurus.Rauhut and Hungerbuhler (2000). "A review of European Triassic theropods." Gaia, 15: 75-88.
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Bird eggshell microstructure is complex and more similar to theropod dinosaurs than to crocodilians. The commonality in eggshell structure is more evidence that birds evolved from theropods.
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First known skull, specimen PVSJ 407, and left maxilla PVSJ 053 A complete Herrerasaurus skull was found in 1988, by a team of paleontologists led by Paul Sereno. Based on the new fossils, authors such as Thomas Holtz and José Bonaparte classified Herrerasaurus at the base of the saurischian tree before the divergence between prosauropods and theropods. However, Sereno favored classifying Herrerasaurus (and the Herrerasauridae) as primitive theropods.
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Named by O.C. Marsh in 1890, the family Ornithomimidae was originally classified as a group of ornithopods. Two years later, Marsh described additional material and realized that ornithomimids were theropods. As relationships within theropods began to be resolved in the 20th century, Friedrich von Huene included Ornithomimidae in his infraorder Coelurosauria. Recognizing the distinctiveness of ornithomimids compared to other coelurosaurs, Rinchen Barsbold placed ornithomimids within their own infraorder, Ornithomimosauria, in 1976.
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Tooth from Megalosaurus Dental findings are frequently used to differentiate between various theropods and to further inform cladistic phylogeny. Tooth morphology and dental evolutionary markers are prone to homoplasy and disappear or reappear throughout history. However, megalosaurids have several specific denture conditions that differentiate them from other basal theropods. One dental condition present in Megalosauridae is multiple enamel wrinkles near the carinae, the sharp edge or serration row of the tooth.
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In the Dinosaur Park Formation, small theropods are rare due to the tendency of their thin-walled bones to be broken or poorly preserved. Small bones of small theropods that were preyed upon by larger ones may have been swallowed whole and digested. In this context, the discovery of a small theropod dinosaur with preserved tooth marks was especially valuable. Possible indeterminate avimimid remains are known from the formation.
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Another noteworthy aspect of the braincase is the prominent hook-like basisphenoidal wing, a feature that is also found in other theropods such as Ceratosaurus, Allosaurus, and Tyrannosaurus.
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Unenlagiinae is a subfamily of dromaeosaurid theropods. Unenlagiines are known from South America and Antarctica. With possible Unenlagiines being known from North America, Madagascar, Europe, and even Australia.
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It is one of the most common fossil vertebrates found in the area, and shared its habitat with other dinosaurian megaherbivores, as well as large theropods and crocodylomorphs.
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However, as in other large tyrannosaurids as well as modern Komodo dragons, juveniles and subadult Tarbosaurus would have filled niches between the massive adults and these smaller theropods.
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Indeterminate remains of non- avian theropods, avialans, ornithischians, and possibly oviraptorosaurs have been found in Ceara state, Brazil. The oviraptorosaurian remains have been re- identified as megaraptoran fossils.
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In the Elrhaz Formation, dinosaurs that lived with Eocarcharia include theropods Kryptops palaios and Suchomimus tenerensis, sauropod Nigersaurus taqueti, and ornithopods Ouranosaurus nigeriensis, Lurdusaurus arenatus, and Elrhazosaurus nigeriensis.
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Several dinosaurs are known from the basin that would have lived alongside Pakasuchus, including large sauropods and theropods. Aquatic crocodyliforms inhabited the rivers along with turtles and fishes.
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As in other theropods, the femur (thigh bone) of a noasaurid had a ridge along the inner rear surface, known as a fourth trochanter. However, in noasaurines and elaphrosaurines (but not necessarily other genera such as Deltadromeus), this fourth trochanter was much smaller and lower than the enlarged crest-like structure present in the majority of basal theropods; only a few other groups of theropods (coelophysoids, coelurosaurs, and a few species of abelisaurids) also have reduced fourth trochanters. In addition, the two subfamilies have a metatarsal II (the foot bone connected to the innermost major toe) which was flattened from the side. Further reductions to this metatarsal were present in noasaurines (particularly Velocisaurus).
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Dinheirosaurus was one of many dinosaurs to have lived in the Lourinhã Formation during the Late Jurassic. Many theropods, sauropods, and especially ornithischians are also from the Lourinhã Formation, which contains a similar fauna to the North American Morrison Formation. Many theropods are known including an unnamed genus of abelisaurid; the allosaurid Allosaurus europaeus; the ceratosaurid Ceratosaurus dentisculatus; the coelurosaurians Aviatyrannis jurassica, and cf. Richardoestesia; an intermediate theropod; and the megalosaurid Torvosaurus gurneyi.
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"Theropods, including birds." in Currie and Koppelhus (eds). Dinosaur Provincial Park, a spectacular ecosystem revealed, Part Two, Flora and Fauna from the park. Indiana University Press, Bloomington. Pp 367–397.
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"Theropods, including birds." in Currie and Koppelhus (eds). Dinosaur Provincial Park, a spectacular ecosystem revealed, Part Two, Flora and Fauna from the park. Indiana University Press, Bloomington. Pp 367–397.
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Novas, Agnolin and Bandyopadhyay, 2004. Cretaceous theropods from India: A review of specimens described by Huene and Matley (1933). Revista del Museo Argentino del Ciencias Naturales. 6(1), 67-103.
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It also includes well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from other previously described therizinosauroids.
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Bone fusion in the scapula, vertebrae, coracoid, and tarsals suggest that the specimen is a mature adult weighing , making it one of the smallest known non-avian theropods thus far discovered.
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Naish, D. (2002). The historical taxonomy of the Lower Cretaceous theropods (Dinosauria) Calamospondylus and Aristosuchus from the Isle of Wight. Proceedings of the Geologists' Association 113: 153-163.Naish, D. 2011.
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Sankofa is an oogenus of prismatoolithid egg. They are fairly small, smooth- shelled, and asymmetrical. Sankofa may represent the fossilized eggs of a transitional species between non-avian theropods and birds.
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The interpretation of dinosaurs as gregarious has also extended to depicting carnivorous theropods as pack hunters working together to bring down large prey.(abstract ) However, this lifestyle is uncommon among the modern relatives of dinosaurs (crocodiles and other reptiles, and birds – Harris's Hawk is a well-documented exception), and the taphonomic evidence suggesting pack hunting in such theropods as Deinonychus and Allosaurus can also be interpreted as the results of fatal disputes between feeding animals, as is seen in many modern diapsid predators. Head wounds from bites suggest that theropods, at least, engaged in active aggressive confrontations. In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures in theropod dinosaurs and the implications for their behavior.
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Partial forelimb of the basal therizinosaur Beipiaosaurus with impressions of feather-like structures, Paleozoological Museum of China Perle and his co-authors of a 1994 redescription of Erlikosauruss skull accepted the synonymy of Segnosauridae with Therizinosauridae and they considered therizinosaurs to have been maniraptoran theropods, the group that also includes modern birds (because they did find Maniraptora to be valid through their analysis). They also discussed the alternative previous hypotheses for therizinosaur affinities and demonstrated faults with them. In 1995, Lev A. Nessov rejected the idea therizinosaurs were theropods; he considered them a distinct group within Saurischia. In 1996, Thomas R. Holtz Jr. found therizinosaurs to group with oviraptorosaurs in a phylogenetic analysis of coelurosaurian theropods. Russell coined the name Therizinosauria for the wider group in 1997.
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New York: Kingfisher Books. Chicago / Turabian - Author Date Citation The scapular blade of Piatnitzkysaurus is shorter and wider than more derived tenaurans. The humerus represents 50 percent of the length of the femur, which is also a primitive condition present among basal theropods. The relative lengths of the ulna in respect to the humerus and femur are also similar to those of basal theropods, which means the forelimbs of Piatnitzkysaurus are proportionally longer than in Allosaurus.
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During the Early Jurassic, many unrelated basal theropods existed in similar geographic regions, as exemplified through the Kayenta Formation and the Upper Elliot Formation. A hypothesis proposed by Smith et al. (2007) was that there may have been resource partitioning within different geographic regions of the Early Jurassic based on differences in body size. This hypothesis, with more evidence, would help explain the lack of endemism observed in the fossil record of the Early Jurassic basal theropods.
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The relationships of Lourinhanosaurus to other theropods have been uncertain, and no firm consensus has been reached as to its classification. Initially regarded as a primitive member of Allosauroidea, it was later discussed as being closely related to Sinraptoridae, a more inclusive clade within Allosauroidea. Recently, some researchers have been favourable to the idea that L. antunesi is not even an allosauroid, but in fact a member of Megalosauroidea, a more primitive group of tetanuran theropods. Benson et al.
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Daemonosaurus is an extinct genus of possible theropod dinosaur from the Late Triassic of New Mexico. Fossils have been found from deposits in the Chinle Formation, which is latest Triassic in age. While theropods had diversified into several specialized groups by this time, Daemonosaurus is likely a very basal theropod (if one at all), and lies outside the clade Neotheropoda. Daemonosaurus is unusual among putative early theropods in that it had a short skull with long protruding teeth.
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However, the exact nature and classification of therizinosaurs within Dinosauria was controversial as was their paleobiology. When Rozhdestventsky first reinterpreted therizinosaurs as dinosaurs he argued that they were unusual theropods that may have used their clawed arms to break open termite mounds or collect fruit. Osmolska and Roniewicz also considered therizinosaurs to be theropods. In 1979, Altangerel Perle named the new species Segnosaurus galbinensis, which although he recognized was an unusual theropod, he did not recognize as a therizinosaur.
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As more information about the link between dinosaurs and birds came to light, the more bird-like theropods were grouped in the clade Maniraptora (also named by Gauthier in 1986). These new developments also came with a recognition among most scientists that birds arose directly from maniraptoran theropods and, on the abandonment of ranks in cladistic classification, with the re-evaluation of birds as a subset of theropod dinosaurs that survived the Mesozoic extinctions and lived into the present.
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The ornamentation of spinosaur tooth enamel, however, developed more irregularly than their serrations and cross section shape. Most non-avian theropods generally had smooth teeth with, at most, minimal wrinkles. Ostafrikasaurus teeth in contrast bore strong lengthwise ridges, a feature also seen in Baryonyx and its close relatives, though their prominence varies between taxa. Spinosaurus teeth, like those of typical theropods, were usually smooth, and Asian forms like Siamosaurus exhibited an increase in the amount of dental ridges.
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The Mugher locality is approximately 151 million years old, about 14 million older than has previously been suggested for Paranthodon, as well as across both southern and eastern Africa. The fauna in the Mugher locality differ from elsewhere of the same time and place in Africa. While the Tendaguru has abundant stegosaurs, sauropods, ornithopods and theropods, the Mugher Mudstone preserves the stegosaur Paranthodon, a hypsilophodontid ornithopod, a probable sauropod, and theropods related to Allosauridae and Dromaeosauridae.
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This environment supported a more diverse and generally larger dinosaur fauna than in earlier times. Kurzanov reported that other theropods, including Tarbosaurus, ornithomimosaurs and therizinosaurs were discovered at the same locality, but these remains have never been reported in detail. If the Nogon Tsav fauna was similar to that of the Nemegt Formation, troodontid theropods, as well as pachycephalosaurs, ankylosaurids and hadrosaurs would also have been present. Titanosaurian sauropods were also potential prey for predators in the Nemegt.
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Balance in theropods was aided by a vertebral column which was almost horizontal, placing the center of gravity near the hips. Tetanurans were named for their zygapophysis-stiffened tails to counterbalance long grasping claws. Deinonychosauria had elongated processes along the neural arches, which stiffened the tail and counterbalanced its long arms. Some theropods, like Tyrannosaurus rex, evolved very small arms relative to body size, which are thought, in part, to have allowed for increased head and jaw size.
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Beipiaosaurus, being considered to be a primitive therizinosauroid, has features which suggest that all therizinosauroids, including the more derived Therizinosauridae, to be coelurosaurian theropods, not sauropodomorph or ornithischian relatives as once believed.
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The Dinosaur HallDinosaur Hall info at azmnh.org features an unnamed coelurosaur nicknamed the "Zuni coelurosaur", a Tarbosaurus skeleton and a Tyrannosaurus rex skull.Dinosaur Hall - Theropods at azmnh.org Also they feature a Gastornis.
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New information on Segisaurus halli, a small theropod dinosaur from the Early Jurassic of Arizona. Journal of Vertebrate Paleontology 25(4): 835-849.Tykoski, 2005. Anatomy, ontogeny and phylogeny of coelophysoid theropods.
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With increasing age, however, they became impervious to the crocodylomorphs, and mature individuals (at least eight to nine years in age) were preyed on by large theropods such as the neovenatorid Siats.
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Endocast of an Amurosaurus brain in right lateral (A), dorsal (B), and ventral (C) views Amurosaurus, a close relative of the taxa from the 2009 study, was the subject of a 2013 paper once again looking into a cranial endocast. A nearly identical EQ range of 2.3 to 3.8 was found, and it was again noted this was higher than that of living reptiles, sauropods and other ornithischians, but different EQ estimates for theropods were cited, placing the hadrosaur numbers significantly below even more basal theropods like Ceratosaurus (with an EQ range of 3.31 to 5.07) and Allosaurus (with a range of 2.4 to 5.24, compared to only 1.6 in the 2009 study); more bird-like coelurosaurians theropods such as Troodon had stated EQs higher than seven. Additionally, the relative cerebral volume was only 30% in Amurosaurus, significantly lower than in Hypacrosaurus, closer to that of theropods like Tyrannosaurus (with 33%), though still distinctly larger than previously estimated numbers for more primitive iguanodonts like Lurdusaurus and Iguanodon (both at 19%). This demonstrated a previously unrecognized level of variation in neuro-anatomy within Hadrosauridae.
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This newer view created an image much more reminiscent of modern flightless birds, such as the ostrich to which this dinosaur's name refers, but would only much later be accepted for all theropods.
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Other dinosaurs known from the Oldman Formation include the hadrosaur Brachylophosaurus, the ceratopsians Coronosaurus and Albertaceratops, ornithomimids, therizinosaurs and possibly ankylosaurs. Theropods included troodontids, oviraptorosaurs, the dromaeosaurid Saurornitholestes and possibly an albertosaurine tyrannosaur.
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Afterwards the remains would then have been regurgitated. However, the presence of vertebrae in the intestines suggests that the exit was wide and that non-avian theropods in this respect were more like present Lepidosauromorpha than extant Archosauria who regurgitate. This is also confirmed by a high bone content in the coprolites of large theropods. Fish contains much calcium and it is possible that the hatchling instinctively sought it out; alternatively, it could have been preferentially fed fish by its parents.
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This hypothesis may also be supported by the hindlegs of Majungasaurus, which were short and stocky, as opposed to the longer and more slender legs of most other theropods. While Majungasaurus would not have moved as fast as other similar-sized theropods, it would have had no trouble keeping up with slow-moving sauropods. The robust hindlimb bones suggest very powerful legs, and their shorter length would have lowered the animal's center of gravity. Thus Majungasaurus may have sacrificed speed for power.
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The earliest part of this time saw the spread of ankylosaurians, iguanodontians, and brachiosaurids through Europe, North America, and northern Africa. These were later supplemented or replaced in Africa by large spinosaurid and carcharodontosaurid theropods, and rebbachisaurid and titanosaurian sauropods, also found in South America. In Asia, maniraptoran coelurosaurians like dromaeosaurids, troodontids, and oviraptorosaurians became the common theropods, and ankylosaurids and early ceratopsians like Psittacosaurus became important herbivores. Meanwhile, Australia was home to a fauna of basal ankylosaurians, hypsilophodonts, and iguanodontians.
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Like other theropods, deinonychosaurs were bipedal; that is, they walked on their two hind legs. However, whereas most theropods walked with three toes contacting the ground, fossilized footprint tracks confirm that most deinonychosaurs held the second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly. The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking).
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Therizinosaurs were the most abundant theropods in the Bayan Shireh Formation in terms of biodiversity; in addition to Segnosaurus, members of the group included Erlikosaurus, Enigmosaurus, and possibly a fourth type. Other theropods included the tyrannosaur Alectrosaurus, the ornithomimid Garudimimus, and the dromaeosaur Achillobator. Other dinosaurs included the ankylosaur Talarurus, the hadrosaur Gobihadros, the sauropod Erketu, and the ceratopsian Graciliceratops. Dinosaur eggs, some of which were identified as Dendroolithidae, as well as footprints of dinosaurs and crocodyliforms, have also been found.
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Both Tikisuchus and the theropods were large terrestrial predators, and, having been found at the same locality, likely came in close contact with one another. The similar lifestyles of the two carnivores may have resulted in competition for the same food sources. Possible prey would have included rhynchosaurs, trilophosaurs, dicynodonts, and aetosaurs. The authors of the original description of Tikisuchus, Sankar Chatterjee and Pranab Majumdar, suggested that competition between Tikisuchus and theropods was low because of abundant food resources and stabilized ecological interactions.
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The study describing Tachiraptor performed a cladistic analysis, establishing its probable evolutionary relationships (phylogeny) by computing an evolutionary tree assuming the fewest evolutionary changes. This analysis showed that Tachiraptor was a basal member of the Neotheropoda, the subgroup encompassing all but the earliest theropods. It thus was placed low in the evolutionary tree of the neotheropods. Tachiraptor was part of the stem leading to the Averostra, the group all theropods belong to from the Middle Jurassic onwards, including the birds.
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The second digit was the longest of the three digits present, while the first was shortest. The structure of the carpal (wrist) bones prevented pronation of the wrist and forced the 'hands' to be held with the palmar surface facing inward (medially), not downward. The first digit of the foot, as in other theropods, was a small dewclaw. However, whereas most theropods had feet with three digits contacting the ground, dromaeosaurids like Velociraptor walked on only their third and fourth digits.
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The next report of clavicles in a dinosaur was in a Russian article in 1983.In an Oviraptor: See the summary and pictures at Contrary to what Heilmann believed, paleontologists now accept that clavicles and in most cases furculae are a standard feature not just of theropods but of saurischian dinosaurs. Up to late 2007 ossified furculae (i.e. made of bone rather than cartilage) have been found in all types of theropods except the most basal ones, Eoraptor and Herrerasaurus.
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The archaic Hateg avian theropods Elopteryx and Balaur bear some similarity to Gargantuavis remains, which may indicate the three form some clade native to the Late Cretaceous European archipelago, though they have ambiguous affinities.
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Carpenter e.a. originally assigned Tanycolagreus to the Coeluridae. Carpenter et alii (2005, p. 44) state that, of the other known Morrison theropods, this genus most closely resembles Coelurus, though it retains more "primitive" features.
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It is also suspected that the dinosaur may have included meat in its diet. The most complete fossil jaw shows that it had serrated blade-like front teeth, reminiscent of those of carnivorous theropods.
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Mesozoic Meanderings 2 196 ppCurrie, P. (2005). "Theropods, including birds." in Currie and Koppelhus (eds). Dinosaur Provincial Park, a spectacular ecosystem revealed, Part Two, Flora and Fauna from the park. Indiana University Press, Bloomington.
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Unidentified taxa are known, including the crurotarsan ?Leidyosuchus, and the theropods ?Struthiomimus, Troodontidae and Tyrannosauridae. The beginning of the Kirtland Formation dates to 74.55 ± 0.22 mya, with the formation ending at around 73.05 ± 0.25 mya.
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Many authors have used a definition similar to "all theropods closer to birds than to Deinonychus",Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.) (2004). The Dinosauria, Second Edition. University of California Press., 861 pp.
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NAISH, D. 2002. The historical taxonomy of the Lower Cretaceous theropods (Dinosauria) Calamospondylus and Aristosuchus from the Isle of Wight. Proceedings of the Geologists’ Association 113: 153–163. Naish (1999, 2002) placed Aristosuchus in Compsognathidae.
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The Therizinosauroidea are unusual theropods in being almost all vegetarian. Fossil Therizinosauroidea are known from 127 to 65 Ma. Maniraptorans include Oviraptorosauria, Deinonychosaurs and birds. They are characterized by an ulna with a curved shaft.
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Judiceratops tigris Judiceratops shared its paleoenvironment with bony fishes, amphibians, the Choristoderan Champsosaurus, the hadrosaur Brachylophosaurus canadensis, the pachycephalosaur Colepiocephale lambei, the theropods Dromaeosaurus, Gorgosaurus and Troodon, and with fellow ceratopsians Albertaceratops, Medusaceratops and Avaceratops.
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Lophostropheus differs from other theropods in several ways. It has features reminiscent of more derived theropods, such as having a ball connection to the front of its neck vertebrae, a socket connection to the front of its tail vertebrae, and a vertical ridge on the ilium. These characteristics have all been interpreted as convergences, however. It also has prominent crests on the tops and bottoms of its neck vertebrae (for which it was named), and an extra pair of cavities in its neck vertebrae, unlike Liliensternus.
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Although megaraptorans were thick-bodied theropods, their bones were heavily pneumatized, or filled with air pockets. The vertebrae, ribs, and the ilium bone of the hip were pneumatized to an extent which was very rare among theropods, only seen elsewhere in taxa such as Neovenator. Other characteristic features include opisthocoelous neck vertebrae and compsognathid-like teeth. The clade was originally named in 2010 as a subset of the family Neovenatoridae, a group of lightly-built allosauroids related to the massive carcharodontosaurids such as Giganotosaurus and Carcharodontosaurus.
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The estimated length of the integumentary structures on the tail is about 60 mm which is seven times the height of a caudal vertebra. Their length and hollow nature argue against of them being subdermal structures such as collagen fibers. Restored skeleton Such dermal structures have previously been reported only in derived theropods and ornithischians, and their discovery in Tianyulong extends the existence of such structures further down in the phylogenetic tree. However, the homology between the ornithischian filaments and the theropods' proto-feathers is not obvious.
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His work has projected Mongolian paleontology into world prominence and helped to form a more modern understanding of the later stages of dinosaur evolution in Eurasia. Barsbold has had considerable influence on dinosaur paleontology in the Communist world. Barsbold's scientific work has made him a leading authority on theropods of the Gobi Desert, starting with his doctoral dissertation on these dinosaurs. As early as 1983, he noted that in different lineages of theropods, many features previously only known from birds had evolved in various combinations (Barsbold 1983).
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The acetabulum is only partly open, and there are only two sacral vertebrae , the lowest number among dinosaurs. The pubic bone has a derived structure, being rotated somewhat posteriorly and folded to create a superficially tetanuran-like terminal expansion, especially prominent in H. ischigulastensis. The hand is primitive in having five metacarpals and the third finger longer than the second, but resembles those of theropods in having only three long fingers, with curved claws. Herrerasaurids also have a hinged mandible, which is also found in theropods.
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Movement at the wrist was also limited in many species, forcing the entire forearm and hand to move as a single unit with little flexibility. In theropods and prosauropods, the only way for the palm to face the ground would have been by lateral splaying of the entire forelimb, as in a bird raising its wing. In carnosaurs like Acrocanthosaurus, the hand itself retained a relatively high degree of flexibility, with mobile fingers. This was also true of more basal theropods, such as herrerasaurs and dilophosaurs.
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Chatterjee and Majumdar considered theropods to be agile pursuit predators while rauisuchids were considered slow ambush predators. Therefore, they suggested that theropods, which were more suited to living in an open environment, outcompeted rauisuchids at the end of the Triassic to become the dominant large land carnivores by the beginning of the Jurassic. However, more recent studies suggest that dinosaurs gained dominance only after the Triassic-Jurassic extinction event in a case of opportunism with no other large archosaurs such as rauisuchids to compete with.
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Above the funnel is a very thin area of the braincase that is formed by deep depressions on the basisphenoids. Cranial elements in several views Smok has several features that are shared with both dinosaurs and crocodile-line archosaurs, making classification difficult. Similarities with theropods include a groove, or antitrochanter, on the ilium bone of the hip that is part of the acetabulum (a depression where the head of the femur attaches to the hip). Smok and theropods also have an anterior trochanter on the femur.
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The tooth proportions of herrerasaurids and basal carnivorous sauropodomorphs each overlap slightly with theropods according to a morphological variation analysis, but herrerasaurids and sauropodomorphs do not overlap with each other. It is inferred that during the Carnian stage of the Triassic, herrerasaurids occupied large predatory niches while small basal sauropodomorphs occupied small carnivorous and omnivorous niches. After the extinction of herrerasaurids and carnivorous sauropodomorphs in the Norian, theropods became the dominant predatory dinosaurs at multiple size tiers, encouraging sauropodomorphs to acquire larger, more herbivory-focused ecologies.
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Allosauroids scaled their limbs relative to their body in a way similar to how other large theropods, like the tyrannosaurids, did. During the Cretaceous, some allosauroids grew to sizes similar to those of the largest tyrannosaurids. These large allosauroids lived in the same time period as the other large theropods found in the upper Morrison and Tendaguru formations. Allosauroids maintained a similar center of mass across all sizes, which is found to be between 37% and 58% of the femoral length anterior to the hip.
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The location of avulsion injuries in theropod scapulae as evidenced by the tendon avulsion in Sue the T. rex suggests that theropods may have had a musculature more complex and functionally different from those of birds.
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Despite their very early occurrence in the fossil record, coelophysoids have a number of derived features that separate them from primitive (basal) theropods. Among the most prominent of these derived features (apomorphies) is the way the upper jaw bones are connected (the premaxilla-maxilla articulation), which is flexible with a deep gap between the teeth in the two bones. A major source of disagreement among theropod experts is whether or not coelophysoids shared a more recent common ancestor with Ceratosauria (sensu stricto) than the ceratosaurs did with other theropods. Most recent analyses indicate the latter, that Coelophysoidea does not form a natural group with the ceratosaurians. Similarly, while Dilophosaurus and similar theropods have traditionally been classified as coelophysoids, several studies published in the late 2000s suggested that they may actually be more closely related to the tetanurans.
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The analysis showed that Thai spinosaurid teeth tended to have the largest difference from the ratios of other, more terrestrial theropods, while those of Spinosaurus from Tunisia and Morocco tended to have the least difference, despite the advanced piscivorous adaptations in the skull observed for this genus. The authors suggested that piscivory and semiaquatic habits may explain how spinosaurids coexisted with other large theropods. By feeding on different prey items and occupying a distinct ecological role, a phenomenon known as niche partitioning, the different types of theropods would have been out of direct competition. Further lines of evidence have since demonstrated that spinosaurids, especially those within the Spinosaurinae, developed strong adaptations for aquatic environments, such as dense limb bones for buoyancy control; reduction of the pelvic girdle; and elongated neural spines on the tail, likely used for underwater propulsion.
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The authors went further, and speculated that pending more complete knowledge of dinosaur skin structures, even the most primitive theropods could turn out to be avifiloplumans. This idea gained tentative support with the discovery of Tianyulong, an ornithischian dinosaur with apparently hollow, filamentous feather-like fibers covering its body. This specimen was described by Zheng and colleagues in 2009, who noted definite similarities between the filaments of Tianyulong and coelurosaurian theropods, supporting the idea that all such structures were homologous with modern feathers, and pushing the origin of feathers back to the origin of dinosaurs or earlier. The discovery of Kulindadromeus supported the idea that feathers were already present in the last common ancestor of ornithischians and theropods, which was either the first dinosaur or the first ornithoscelidan depending on how ornithischians are related to other dinosaurs.
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Previous workers had suggested that non-avian theropods might — like birds — possess post-cranial air sacs, and Mirischia seems to confirm that. Another notable trait is the exceptional thinness of the bone wall of all skeletal elements.
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Cryolophosaurus ( or ; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about long and in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub- adult. Cryolophosaurus is known from a skull, a femur and other material, the skull and femur of which have caused its classification to vary greatly.
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Although the vast majority of feather discoveries have been in coelurosaurian theropods, feather-like integument has also been discovered in at least three ornithischians, suggesting that feathers may have been present on the last common ancestor of the Ornithoscelida, a dinosaur group including both theropods and ornithischians. It is possible that feathers first developed in even earlier archosaurs, in light of the discovery of highly feather-like pycnofibers in pterosaurs. Crocodilians also possess beta keratin similar to those of birds, which suggests that they evolved from common ancestral genes.
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Contemporaries of Limusaurus in the Wucaiwan locality include the theropods Haplocheirus, Zuolong, Guanlong, Aorun, and Shishugounykus; the sauropod Mamenchisaurus; the ornithischians Gongbusaurus, Yinlong, and Hualianceratops; the cynodont Yuanotherium; the mammal Acuodulodon; the crocodyliform Nominosuchus and another unnamed crocodyliform found with the holotype specimen of Limusaurus; and the turtles Xinjiangchelys and Annemys. Small theropod dinosaurs are generally rare in the fossil record. According to Eberth and colleagues, the high incidence of Limusaurus indicates that the abundance of small theropods is underestimated elsewhere as these animals are generally less likely to fossilize.
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However, Evers and colleagues noted that a more thorough biomechanical analysis is required for confirmation of this condition in Sigilmassasaurus. Several large theropods (more than one tonne) are known from the Cenomanian of northern Africa, raising questions about how such animals would have coexisted. Species of Spinosaurus, the longest known theropod, have been found in both Morocco and Egypt, as has the huge Carcharodontosaurus. Two smaller theropods, Deltadromeus and Bahariasaurus, have also been found in Morocco and Egypt, respectively, and may be closely related or possibly the same genus.
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The abundant carnivorous theropods would have then likely turned to the lush aquatic life as a primary food source. They also hypothesized that following storm events, pterosaur and fish carcasses might have washed up on the shoreline, providing theropods with plenty of carrion. Multiple piscivorous animals were present in the formation, which might in theory have led to high competition. Aureliano and colleagues stated there must have, therefore, been some degree of niche partitioning, where different animals would have fed on prey of varied sizes and locations within the lagoon.
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The pes (foot) consisted of three weight- bearing digits, numbered II–IV. Digit I, which in theropods is usually reduced to a dewclaw that does not touch the ground, is not preserved in the holotype. Marsh, in his original 1884 description, assumed that this digit was lost in Ceratosaurus, but Charles Gilmore, in his 1920 monograph, noted an attachment area on the second metatarsal demonstrating the presence of this digit. Uniquely among theropods, Ceratosaurus possessed small, elongated, and irregularly formed osteoderms (skin bones) along the midline of its body.
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The impressions for the olfactory bulbs, which house the sense of smell, are well-preserved. While similar to those of Allosaurus, they were smaller than in Tyrannosaurus, which is thought to have been equipped with a very keen sense of smell. The semicircular canals, which are responsible for the sense of balance and therefore allow for inferences on habitual head orientation and locomotion, are similar to those found in other theropods. In theropods, these structures are generally conservative, suggesting that functional requirements during locomotion have been similar across species.
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The bone tissues were well vascularized and had a fibro-lamellar structure similar to that found in other theropods and the sauropodomorph Massospondylus. The plexiform (woven) structure of the bones suggested rapid growth, and Dilophosaurus may have attained a growth rate of per year early in life. Welles found that the replacement teeth of Dilophosaurus and other theropods originated deep inside the bone, decreasing in size the farther they were from the alveolar border. There were usually two or three replacement teeth in the alveoli, with the youngest being a small, hollow crown.
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Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not the only early members of this group to abandon carnivory. Several other lineages of early maniraptors show adaptations for an omnivorous diet, including seed- eating (some troodontids) and insect-eating (many avialans and alvarezsaurs). Oviraptorosaurs, ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some early theropods (such as Masiakasaurus knopfleri and the spinosaurids) appear to have specialized in catching fish.
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Predatory Dinosaurs of the World. New York: Simon and Schuster. Paul states that: > Many theropods have been united into new groups... but the placement of > Archaeopteryx and the sickle-clawed dromaeosaurs in the same family is by > far the most radical–yet it is also one of the most necessary... how alike, > in detail after detail, dromaeosaurs and Archaeopteryx were. However, the name Deinonychosauria was coined by Ned Colbert and Dale Russell in 1969, and defined as a clade (all theropods closer to dromaeosaurids than to birds) by Jacques Gauthier in 1986.
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The pelvis was shortened at the front, a feature found among bird-like theropods but uncommon among theropods as a whole. The pubic bone was directed backwards and down in parallel with the ischium; this backwards orientation of the pubic bone is known as the condition. This feature is only known from birds and their closest coelurosaurian relatives while other theropod dinosaurs had forwards-directed pubic bones. The pubic bone was elongated, flattened sideways, and had an ellisoid projection or "boot" at the front of its lower end.
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Reconstructed skeleton of Alxasaurus from China, the completeness of which confirmed therizinosaurs as theropods in 1993 In a 1990 review article, Barsbold and paleontologist Teresa Maryańska found Segnosauria to be a rare and aberrant group of saurischians, in an unresolved position among sauropodomorphs and theropods, probably closer to the former. They therefore listed them as Saurischia sedis mutabilis ("position subject to change"). Though they agreed the hindlimbs assigned to Therizinosaurus in 1982 were segnosaurian, they did not consider this justification for Therizinosaurus itself being a segnosaur, since it was only known from forelimbs.
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Palaeontologist Lev Alexandrovich Nessov rejected that therizinosaurs were theropods in 1995, and instead considered them a distinct group within saurischia.Nessov, L. A., 1995, Dinosaurs of northern Eurasia: New data about assemblages, ecology and paleobiogeography. Saint Petersburg In 1996, paleontologist Thomas R. Holtz Jr. found therizinosaurs to group with oviraptorosaurs in a phylogenetic analysis of coelurosauria. In 1999, paleontologist Xing Xu and colleagues described a small, basal therizinosauroid from China, Beipiaosaurus, which confirmed that the group belonged among the coelurosaurian theropods, and that similarities with prosauropods had evolved independently.
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Theropoda It has been hypothesized that male theropods possessed a retractable penis, a feature similar to modern day crocodilians. Crocodilian skeletons were examined to determine whether there is a skeletal component that is distinctive between both genders, to help provide an insight on the physical disparities between male and female theropods. Findings revealed the caudal chevrons of male crocodiles, used to anchor the penis muscles, were significantly larger than those of females. There have been criticisms of these findings, but it remains a subject of debate among advocates and adversaries.
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Three cervicals of the diplodocid are preserved, and from their size it is possible that the taxon was also a dwarf. The stegosaurian and variety of theropods only preserve teeth, with the exception of a few bones possibly from a taxon in Ceratosauridae. Isolated teeth show that there were at least four different types of theropods present at the locality, including the megalosaurid Torvosaurus sp. as well as an additional megalosaurid and indeterminate members of the Allosauridae and Ceratosauria; and there are also the oldest teeth known from Velociraptorinae.
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These 'traps' or 'bonebeds' are unusual in that they consist of vertically stacked skeletons of numerous non-avian theropods in deep pits. The pits are filled with a mix of alluvial and volcanic mudstone and sandstone and appear to have been created by the trampling and wallowing of large dinosaurs. Small theropods and vertebrates then became mired in these pits, dying and being forced deeper by the activities of the large dinosaurs and the struggles of later victims. The high quality of preservation suggests a rapid burying of the carcasses.
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Imprints of dinosaurs were made in carbonate mud, after they were infilled with marl. Dinosaur tracks have been assigned to sauropods, theropods and ornithopods.Rupelo Formation at Fossilworks.org The municipality of Mambrillas de Lara has created a dinosaur park.
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Compsognathids share a variety of characteristics. The genera in this family demonstrate traits that are characteristic of theropods, such as smaller forelimbs than hind legs. Size, feathers, and metacarpal size are among the most important classifying common characteristics.
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Like other theropods, the phalangeal formula (the number of phalanges per digit) is 2-3-4-5. The 3rd digit is the longest, and the 4th is slightly longer than the 2nd. The toe claws are moderately curved.
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Like all stegosaurs, Chungkingosaurus was a herbivore. Chungkingosaurus is thought to have coexisted with large plant-eaters and stegosaurids such as Chialingosaurus, Tuojiangosaurus, Mamenchisaurus, and Omeisaurus. It may have also been preyed upon by theropods such as Yangchuanosaurus.
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It belongs to the ornithoid-ratite morphotype, a grouping which primarily includes paleognathous birds and non-avian theropods. Continuoolithus canadensis has one junior synonym, Spongioolithus hirschi, which was originally classified as a distinct oogenus and oospecies of Elongatoolithidae.
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By contrast, in the lower Aguja Formation. the teeth of Dryadissector outnumber those of all theropod species combined. The lower Aguja may therefore preserve a rare ecosystem in which varanoid lizards outcompeted small theropods as the dominant mesopredators.
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Another estimate can be gleaned from the fact that its tail vertebrae and fibulae are roughly equal in length to those of Torvosaurus tanneri, which had been estimated at , thus making Wiehenvenator one of the largest known European theropods.
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Irritator may have had semiaquatic habits, and inhabited the tropical environment of a coastal lagoon surrounded by dry regions. It coexisted with other carnivorous theropods as well as turtles, crocodyliforms, and a large number of pterosaur and fish species.
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The Cabreira et al. (2016) analysis is notable for excluding several other traditional basal theropods from the group. These include Daemonosaurus, Tawa, Chindesaurus, and Eodromaeus, which are considered basal saurischians according to their results. Skeletal reconstruction of Nhandumirim waldsangae.
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Handbuch der Palaeoherpetologie Teil 18. Gustav Fischer Verlag, Stuttgart. 124 pp. However, Tyrannosauropus are Campanian in age, pre-dating the Maastrichtian age for Tyrannosaurus, and the morphology of the footprints more closely resembles those of hadrosaurid dinosaurs than those of theropods.
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The Qiupa Formation has yielded numerous dinosaur fossils, particularly eggs. The remains of various theropods such as troodontids, dromaeosaurids and oviraptorosaurs have been found. In addition, indeterminate remains of sauropods, ornithopods, ankylosaurs, lizards, turtles and a possible avian bone are reported.
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Similarly, scavenging theropods were not trapped due to their lower body weights, combined with proportionally larger feet. There is no indication of herding, or of catastrophic burial of such a herd, or catastrophic accumulation of animals that previously died isolated elsewhere.
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It may have had strong neck musculature as evidenced by the morphology of its vertebrae (backbones). Sigilmassasaurus may have had semiaquatic habits and a largely piscivorous (fish-eating) diet. It coexisted with other large theropods in the Kem Kem Formation.
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The osteology of Syntarsus kayentakatae and its implications for ceratosaurid phylogeny. Unpublished Masters Thesis, University of Texas at Austin, 217 pp. agreed. Gay (2010) described the specimen as the new tetanurine taxon Kayentavenator elysiae,Gay, 2010. Notes on Early Mesozoic theropods.
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Ichthyoconodon's teeth were found in marine deposits, alongside taxa like hybodontid sharks, ornithocheirid pterosaurs,Wilton, Mark P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. . ray-finned fish and sea turtles, as well as several terrestrial taxa like theropods.
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Therrien, F., & Henderson, D. M. (2007). My theropod is bigger than yours… or not: estimating body size from skull length in theropods. Journal of Vertebrate Paleontology, 27(1), 108-115. Sinosauropteryx is the most similar to Compsognathus, measuring at most long.
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The rock formation preserves fossils from the Late Jurassic period of the Mesozoic Era. Fossils of Chilesaurus (147 Ma) were found in the Aysén Region of Patagonia. It is an extinct genus of theropods in the family Tetanurae.news.nationalgeographic.com National Geographic.
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The region had forests dominated by gymnosperms (such as Araucaria, Mataia and Podocarpus) and Lycopodiopsida (clubmosses). Some angiosperms were also present. Dinosaurs such as theropods dwelt on the peninsula and probably evolved into numerous endemic forms (Stilwell et al. 2006).
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This ridge-like structure is heavy-built compared to other dromaeosaurids. At the side and away from the main body, the surface is very rough, possibly attaching m. flexor tibialis internus-1 in life as seen in other theropods and crocodiles.
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Bulletin of the Museum of Northern Arizona 57: 1–160. Syntarsus rhodiensensis,Raath MA (1990) Morphological variation in small theropods and its meaning in systematic: evidence from Syntarsus rhodiensensis. In Carpenter K, Currie PJ eds. Dinosaur systematics: approaches and perspectives.
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Conchoraptor shared its habitat with other oviraptorosaurs including Avimimus and Nomingia, other theropods include troodontids such as Tochisaurus and Zanabazar, the tyrannosaurids Alioramus and Tarbosaurus. Ornithischians include the pachycephalosaurs Homalocephale and Prenocephale, the hadrosaurid Saurolophus, the ankylosaurs Saichania and Tarchia.
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Remains of the following dinosaurs have been found in the formation:Currie, P.J. 2005. Theropods, including birds. In: Currie, P.J., and Koppelhus, E.B. (eds), Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Indiana University Press: Bloomington and Indianapolis, p. 367-397. .
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Mammal fossils are rare in the Nemegt Formation, but many birds, including the enantiornithine Gurilynia, the hesperornithiform Judinornis, as well as Teviornis, a possible anseriform, have been found. Herbivorous dinosaurs discovered in the Nemegt Formation include ankylosaurids such as Tarchia, the pachycephalosaurian Prenocephale, large hadrosaurids such as Saurolophus and Barsboldia, and sauropods such as Nemegtosaurus and Opisthocoelicaudia. Predatory theropods that lived alongside Gallimimus include tyrannosauroids such as Tarbosaurus, Alioramus and Bagaraatan, and troodontids such as Borogovia, Tochisaurus and Zanabazar. Herbivorous or omnivorous theropods include therizinosaurs, such as Therizinosaurus, as well as oviraptorosaurians, such as Elmisaurus, Nemegtomaia, and Rinchenia.
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Skull of juvenile P. grangeri The habitat of Pinacosaurus consisted of a semi-desert interspersed with oases. No large theropods are known to have inhabited the ecosystem, though smaller ones like Velociraptor were present. It has been suggested that the relatively light build of Pinacosaurus was an adaptation to gain agility to better fight small theropods, the moderately large club being fast enough to hit these swift targets. In the group of juveniles found together at Bayan Mandahu, the individuals were all oriented into the same direction, suggesting they represent a travelling true herd simultaneously killed and covered by a sandstorm.
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Spinosaurus had a significantly smaller pelvis (hip bone) than that of other giant theropods, with the surface area of the illium (main body of the pelvis) half that of most members of the clade. The hind limbs were short, at just over 25 percent of the total body length, with the tibia (calf bone) being longer than the femur (thigh bone). Unlike in other theropods, the hallux (or fourth toe) of Spinosaurus touched the ground, and the phalanges of the toe bones were unusually long and well-built. At their ends were shallow claws that had flat bottoms.
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Full text currently online at and Detailed anatomical analyses can be found at Comparison between the air sacs of Majungasaurus and a bird Evidence of air sacs has also been found in theropods. Studies indicate that fossils of coelurosaurs, This is also one of several topics featured in a post on Naish's blog, - note Mirischia was a coelurosaur, which Naish believes was closely related to Compsognathus. ceratosaurs, and the theropods Coelophysis and Aerosteon exhibit evidence of air sacs. Coelophysis, from the late Triassic, is one of the earliest dinosaurs whose fossils show evidence of channels for air sacs.
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They differed from teeth of other theropods, which seemed geared towards tearing or cutting off seized body parts. Closeup of reconstructed skull and neck Irritator shared with crocodilians a stiff secondary palate and reduced antorbital fenestrae. In 2007, a finite-element analysis study by British paleontologist Emily J. Rayfield and colleagues found that these attributes, present in other spinosaurids as well, made the skull more resistant to torsion from prey item loads when feeding. The authors pointed out that in contrast, most theropods lacked secondary palates and had large antorbital fenestrae, exchanging strength for lighter skull builds.
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Digital endocranial endocast of the braincase of specimen NCSM 14345 In 2005, scientists reconstructed an endocast (replica) of an Acrocanthosaurus cranial cavity using computed tomography (CT scanning) to analyze the spaces within the holotype braincase (OMNH 10146). In life, much of this space would have been filled with the meninges and cerebrospinal fluid, in addition to the brain itself. However, the general features of the brain and cranial nerves could be determined from the endocast and compared to other theropods for which endocasts have been created. While the brain is similar to many theropods, it is most similar to that of allosauroids.
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Cast of Coelophysis, with which Dilophosaurus has often been grouped, Redpath Museum Welles thought Dilophosaurus a megalosaur in 1954, but revised his opinion in 1970 after discovering that it had crests. By 1974, Welles and the American paleontologist Robert A. Long found Dilophosaurus to be a ceratosauroid. In 1984 Welles found that Dilophosaurus exhibited features of both Coelurosauria and Carnosauria, the two main groups into which theropods had hitherto been divided, based on body size, and he suggested this division was inaccurate. He found Dilophosaurus to be closest to those theropods that were usually placed in the family Halticosauridae, particularly Liliensternus.
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After some time, the animal stood up and moved forwards, with the left foot first, and once fully erect, it walked across the rest of the exposed surface, while leaving thin drag marks with the end of the tail. Crouching is a rarely captured behavior of theropods, and SGDS 18.T1 is the only such track with unambiguous impressions of theropod hands, which provides valuable information about how they used their forelimbs. The crouching posture was found to be very similar to that of modern birds, and shows that early theropods held the palms of their hands facing medially, towards each other.
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As such a posture therefore evolved early in the lineage, it may have characterized all theropods. Theropods are often depicted with their palms facing downwards, but studies of their functional anatomy have shown that they, like birds, were unable to pronate or supinate their arms. The track showed that the legs were held symmetrically with the body weight distributed between the feet and the metatarsals, which is also a feature seen in birds such as ratites. Milner and colleagues also dismissed the idea that the Kayentapus minor track reported by Weems showed a palm imprint made by a quadrupedally walking theropod.
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Restoration The filamentous integumentary structures are preserved on three areas of the fossil: in one patch just below the neck, another one on the back, and the largest one above the tail. The hollow filaments are parallel to each other and are singular with no evidence of branching. They also appear to be relatively rigid, making them more analogous to the integumentary structures found on the tail of Psittacosaurus than to the proto-feather structures found in avian and non-avian theropods. Among the theropods, the structures in Tianyulong are most similar to the singular unbranched proto- feathers of Sinosauropteryx and Beipiaosaurus.
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Procumbent teeth project forward from the tips of the upper and lower jaws, which is highlighted in the species name chauliodis that roughly means "buck-toothed". Daemonosaurus is unique among Triassic theropods because it has an unusually short snout, and all other early theropods had long heads and jaws. Like the coelophysoids, Daemonosaurus has a kink in its upper jaws, between the maxilla and the premaxilla. The proportionately large orbit, the short snout, and the apparent lack of fusion between the bones of the braincase suggest that the holotype specimen CM 76821 may be an example of a juvenile dinosaur.
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Anchiornis huxleyi is an important source of information on the early evolution of birds in the Late Jurassic period. Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropod dinosaurs, and more specifically, they are members of Maniraptora, a group of theropods which includes dromaeosaurids and oviraptorosaurs, among others. As scientists have discovered more theropods closely related to birds, the previously clear distinction between non-birds and birds has become blurred. Recent discoveries in the Liaoning Province of northeast China, which demonstrate many small theropod feathered dinosaurs, contribute to this ambiguity.
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Of particular note have been the fossils of the Yixian Formation, where a variety of theropods and early birds have been found, often with feathers of some type. Birds share over a hundred distinct anatomical features with theropod dinosaurs, which are now generally accepted to have been their closest ancient relatives. They are most closely allied with maniraptoran coelurosaurs. A minority of scientists, most notably Alan Feduccia and Larry Martin, have proposed other evolutionary paths, including revised versions of Heilmann's basal archosaur proposal, or that maniraptoran theropods are the ancestors of birds but themselves are not dinosaurs, only convergent with dinosaurs.
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The Huincul Formation is among the richest Patagonian vertebrate associations, preserving fish including dipnoans and gar, chelid turtles, squamates, sphenodonts, neosuchian crocodilians, and a wide variety of dinosaurs. Vertebrates are most commonly found in the lower, and therefore older, part of the formation. In addition to Argentinosaurus, the sauropods of the Huincul Formation are represented by another titanosaur, Choconsaurus, and several rebbachisaurids including Cathartesaura, Limaysaurus, and some unnamed species. Theropods including carcharodontosaurids such as Mapusaurus, abelisaurids including Skorpiovenator, Ilokelesia, and Tralkasaurus, noasaurids such as Huinculsaurus, paravians such as Overoraptor, and other theropods such as Aoniraptor and Gualicho have also been discovered there.
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There were around six to eight denticles per mm (0.039 in), a much larger number than in large-bodied theropods like Torvosaurus and Tyrannosaurus. Some of the teeth were fluted, with six to eight ridges along the length of their inner sides and fine-grained (outermost layer of teeth), while others bore no flutes; their presence is probably related to position or ontogeny (development during growth). The inner side of each tooth row had a bony wall. The number of teeth was large compared to most other theropods, with six to seven teeth in each premaxilla and thirty-two in each dentary.
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Reconstructed necks of the spinosaurids Sigilmassasaurus (A) and Baryonyx (B), showing their curvature Initially thought to have lacked the sigmoid curve typical of theropods, the neck of Baryonyx does appear to have formed an S shape, though straighter than in other theropods. The cervical vertebrae of the neck tapered towards the head and became progressively longer front to back. Their (the processes that connected the vertebrae) were flat, and their (processes to which neck muscles attached) were well developed. The (the second neck vertebra) was small relative to the size of the skull and had a well-developed .
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In 2017, similarities between the skeletons of Heterodontosaurus and the early theropod Eoraptor were used by palaeontologist Matthew G. Baron and colleagues to suggest that ornithischians should be grouped with theropods in a group called Ornithoscelida. Traditionally, theropods have been grouped with sauropodomorphs in the group Saurischia. In 2020, palaeontologist Paul-Emile Dieudonné and colleagues suggested that members of Heterodontosauridae were basal marginocephalians not forming their own natural group, instead progressively leading to Pachycephalosauria, and were therefore basal members of that group. This hypothesis would reduce the ghost lineage of pachycephalosaurs and pull back the origins of ornithopods back to the Early Jurassic.
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Holtz noted that tyrannosaurids and some closely related groups had significantly longer distal hindlimb components (shin plus foot plus toes) relative to the femur length than most other theropods, and that tyrannosaurids and their close relatives had a tightly interlocked metatarsus (foot bones). The third metatarsal was squeezed between the second and fourth metatarsals to form a single unit called an arctometatarsus. This ankle feature may have helped the animal to run more efficiently. Together, these leg features allowed Tyrannosaurus to transmit locomotory forces from the foot to the lower leg more effectively than in earlier theropods.
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Liliensternus has five fingers, much like its contemporaries, but its fourth and fifth digits are smaller than the rest, a possible transitional stage between the five fingered theropods of the Triassic and the three fingered theropods of the Jurassic. Rauhut et al. (1998) noted that the remains may represent a juvenile or subadult individual based on the presence of only two fused sacrals and the fact that the neurocentral sutures are still visible in the vertebrae. A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms.
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These large theropods therefore may have dominated both halves of the world during the Jurassic. The family Megalosauridae was first defined by Thomas Huxley in 1869, yet it has been contested throughout history due to its role as a "waste-basket" for many partially described dinosaurs or unidentified remains. In the early years of paleontology, most large theropods were grouped together and up to 48 species were included in the clade Megalosauria, the basal clade of Megalosauridae. Over time, most of these taxa were placed in other clades and the parameters of Megalosauridae were narrowed significantly.
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As early paleontologists and researchers found more dinosaur bones in the surrounding area, they attributed them all to M. bucklandii since it was the only named and described dinosaur at this point in history. Therefore, the species was initially described and classified by a mass of possibly unrelated characteristics. Modern paleontology first began to approach the problematic cladistic separation of Megalosauridae during the early 20th century. Fredrich von Huene separated carnivorous theropods, which had all been grouped into the broad category of megalosaurids, into two distinct families of larger, more giant sized and smaller, more lightly built theropods.
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Although classified as an allosaurid by Huene and Matley (1933) and Molnar et al. (1990) because of superficial similarities with the axis vertebrae of Allosaurus, a 2004 review of Lameta Formation theropods found it to be similar to members of Abelisauroidea, including Carnotaurus and Indosaurus, necessitating the placement of Compsosuchus as an abelisauroid.F. E. Novas, F. L. Agnolin, and S. Bandyopadhyay, 2004, "Cretaceous theropods from India: a review of specimens described by Huene and Matley (1933)", Revista del Museo Argentino de Ciencias Naturales, nuevo serie 6(1): 67-103Molnar, Kurzanov and Dong, 1990. Carnosauria. In Weishampel, Dodson and Osmolska (eds.).
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Fellow theropods include the large Achillobator, and the deinocheirid Garudimimus. Other herbivorous dinosaurs are represented by the ankylosaurs Talarurus and Tsagantegia, small marginocephalians Amtocephale and Graciliceratops, the hadrosauroid Gobihadros, and the sauropod Erketu. Other fauna include semiaquatic reptiles like crocodylomorphs and nanhsiungchelyid turtles.
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The Tongfosi Formation is a Late Cretaceous (Cenomanian) geologic formation of the Yanji Group in China.Tongfosi Formation in the Paleobiology Database Fossil ornithopod tracks of iguanodontids and theropods have been reported from the fluvial sandstones of the formation.Matsukawa et al., 1995Weishampel et al.
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Some genera are shared in Morrison and Lourinhã, such as Torvosaurus,Hendrickx, C, Mateus O. 2014. Torvosaurus gurneyi n. sp., the largest terrestrial predator from Europe, and a proposed terminology of the maxilla anatomy in nonavian theropods, 03. PLoS ONE. 9:e88905.
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481 pp. However, most later researchers have used it to denote a broader group. Neotheropoda was first defined as a clade by Paul Sereno in 1998 as Coelophysis plus modern birds, which includes almost all theropods except the most primitive species.Sereno, 1998.
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Paleofauna that lived alongside Geminiraptor in the lower bed, included other Theropods: Falcarius and Yurgovuchia. The sauropod Mierasaurus, the large iguanodontian Iguanacolossus and the turtle Naomichelys. There are also indeterminate Goniopholidids crocodiles and an unnamed velociraptorine known from the Lower Yellow Cat.
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This means that Dinheirosaurus lived alongside many theropods, sauropods, thyreophorans and ornithopods, as well as at least one other diplodocid. Dinheirosaurus is a diplodocid, a relative of Apatosaurus, Diplodocus, Barosaurus, Supersaurus, and Tornieria. Among those, the closest relative to Dinheirosaurus is Supersaurus.
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Glut, D. F. (1999). Dinosaurs, the Encyclopedia, Supplement 1: McFarland & Company, Inc., 442pp. Although the skull of D. sinensis sports large nasolacrimal crests superficially like those reconstructed in D. wetherilli, features elsewhere in the skeleton suggest it is closer to tetanuran theropods.
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Due to this size increase over time, Megalosauridae appear to follow a size increase pattern similar to that of other giant sized theropods like Spinosauridae. This pattern follows Cope's Rule, the postulation by paleontologist Edward Cope about evolutionary increase in body size.
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Among dinosaurs, theropods had exceptionally large eyes. Deinonychosaurians, especially troodontids, had forward-facing eyes, suggesting stereoscopic vision and improved depth perception. Tyrannosauroid snouts allowed for a 55˚ binocular field of view, less than a modern human but more than their hadrosaurid prey.
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The infraorder Coelurosauria, coined in 1914 by Friedrich von Huene, was traditionally a taxonomic wastebasket into which all small theropods were placed.Paul (1988a), p. 188–189; Norman (1990), p. 280 Ornitholestes, due to its small size, was therefore generally classified as a coelurosaur.
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Evgeny Aleksandrovich Maleev (, ; 25 February 1915 - 12 April 1966) was a Soviet paleontologist who did most of his research on reptiles and Asian fossils, such as the naming of the ankylosaur Talarurus and theropods Tarbosaurus and Therizinosaurus along with the family Therizinosauridae.
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Yi was placed in the Scansoriopterygidae, a group of maniraptoran theropods. A cladistic analysis failed to resolve its exact relationships with the other known scansoriopterygids, Epidendrosaurus and Epidexipteryx. In the analysis the Scansoriopterygidae was recovered as the most basal clade of the Paraves.
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This growth pattern is unusual among theropods, but is also seen in derived ("advanced") tyrannosaurids. Also unusual is that, even at this early stage of development, the nasal bones are fused. Coincidentally, tyrannosaurids also show fusion of the nasals early in development.
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Chicago A cladistic analysis in 2010 by Jin et al. found Dictyoolithus to be basal theropod eggs. Similarly, Sellés and Galobart in 2015 found Dictyoolithus to be basal theropods, and considered it to be the eggs of megalosauroids.Sellés, A. G., & Galobart, À. (2015).
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Li et al. referred this taxon to Sinraptoridae – a group of carnosaurian theropods,F. Li; Peng G.; Ye Y.; Jiang S.; and Huang, D. (2009). "A new carnosaur from the Late Jurassic of Qianwei, Sichuan, China". Acta Geologica Sinica 83(9): 1203–1213. Abstract.
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Restoration The phylogenetic position of Acheroraptor was explored by Evans et al. (2013) using several data matrices. Both specimens of Acheroraptor were coded as a single taxon into Turner et al. (2012) data matrix, an extensive phylogenetic analysis of theropods that focuses on maniraptorans.
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Ronald Tykoski agreed (2005) and suggested that certain skull features of the type specimen suggested that it was young, specifically, the skull bones are not completely fused, relatively large orbits, and a short snout.Tykoski, 2005. Anatomy, ontogeny and phylogeny of coelophysoid theropods. PhD Dissertation.
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Halticosaurus orbitoangulatus. In 2000, Rauhut and Hungerbuhler reassigned this material to the genus Saltoposuchus, a crocodylomorph, based on the morphology of the teeth and the antorbital fenestra in the skull.Rauhut, O.M.W. & Hungerbühler, A. (2000) "A review of European Triassic theropods." Gaia, 15: 75-88.
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Unlike many pseudosuchids and theropods, Smok does not have pneumatic areas, or air pockets, in the braincase. It also has several features that link it with primitive archosauromorphs, including the presence of a postfrontal bone on the skull and a closed acetabulum in the hip.
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Without the need for herbivores to migrate to find food, and theropods to migrate after herbivores, a whole ecosystem could evolve secluded from interbreeding. The theory also supported why the dinosaurs adorned such features like the 15 horns of Kosmoceratops, they were for sexual selection.
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As reflected by at least 31 therizinosaurid footprints at the Cantwell Formation of Alaska, some species formed small herds, which is consistent with the complex brain and ear structure in these theropods. The co-occurrence with hadrosaurids on this area may also indicate that these very different dinosaurs benefited from an ecological interaction, just as some animals today congregate together for mutual beneficial reasons, such as augmented resource acquisition or lesser predation pressure. It is also possible that a herd of hadrosaurids and therizinosaurids walked across this terrain at different times and did not encounter each another. Regardless of these explanations, the therizinosaurid trackway reflects a gregarious behaviour in these theropods.
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Bahariasauridae is a potential family of averostran theropods that might include a handful of African and South American genera, such as Aoniraptor, Bahariasaurus, Deltadromeus, and Gualicho. The placement of these theropods is controversial, with some studies placing them as basal ceratosaurs possibly related to Noasauridae (which they may also include the otherwise noasaurid subfamily Elaphrosaurinae), others classifying them as megaraptorans, basal neovenatorids, or basal coelurosaurs. There is also a possibility the group might not be monophyletic, as a monograph on the vertebrate diversity in the Kem Kem Beds published in 2020 found Bahariasaurus to be nomen dubium. In the same paper Deltadromeus is classified as an abelisaurid.
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They found that the frontal bones of Irritator, Spinosaurus, and Sigilmassasaurus were similar in being arched, concave on top, and narrowed at the front; features that would have resulted in the eyes being positioned further up on the head than in other theropods. In particular, the broad lower jaw and narrowed frontals of Irritator resulted in the orbits facing at a steep incline towards the midline of the skull, whereas most theropods had laterally facing orbits. These traits would have permitted the animal to see above the waterline when submerged. In 2018, Aureliano and colleagues conducted an analysis on the Romualdo Formation tibia fragment.
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Because it survived the attack, Carpenter suggested that it may have outmaneuvered or outrun its attacker, or that the damage to its tail was incurred by the hadrosaurid using it as a weapon against the tyrannosaur. [not printed until 2000] Another specimen of E. annectens, pertaining to a long individual from South Dakota, shows evidence of tooth marks from small theropods on its lower jaws. Some of the marks are partially healed. Michael Triebold, informally reporting on the specimen, suggested a scenario where small theropods attacked the throat of the edmontosaur; the animal survived the initial attack but succumbed to its injuries shortly thereafter.
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Dry season at the Mygatt-Moore Quarry showing Ceratosaurus (center) and Allosaurus fighting over the desiccated carcass of another theropod Within the Morrison Formation, Ceratosaurus fossils are frequently found in association with those of other large theropods, including the megalosaurid Torvosaurus and the allosaurid Allosaurus. The Garden Park locality in Colorado contained, besides Ceratosaurus, fossils attributed to Allosaurus. The Dry Mesa Quarry in Colorado, as well as the Cleveland-Lloyd Quarry and the Dinosaur National Monument in Utah, feature, respectively, the remains of at least three large theropods: Ceratosaurus, Allosaurus, and Torvosaurus. Likewise, Como Bluff and nearby localities in Wyoming contained remains of Ceratosaurus, Allosaurus, and at least one large megalosaurid.
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Cast of the hand of C. nasicornis (AMNH 27631): Most phalanges of the fingers are missing. The strongly shortened metacarpals and phalanges of Ceratosaurus raise the question whether the manus retained the grasping function assumed for other basal theropods. Within the Ceratosauria, an even more extreme manus reduction can be observed in abelisaurids, where the forelimb lost its original function, and in Limusaurus. In a 2016 paper on the anatomy of the Ceratosaurus manus, Carrano and Jonah Choiniere stressed the great morphological similarity of the manus with those of other basal theropods, suggesting that it still fulfilled its original grasping function, despite its shortening.
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Scientists have described many dinosaurs from the Nemegt Formation, including the ankylosaurid Saichania, and pachycephalosaur Prenocephale. By far the largest predator known from the formation, adult Tarbosaurus most likely preyed upon large hadrosaurs such as Saurolophus and Barsboldia, or sauropods such as Nemegtosaurus, and Opisthocoelicaudia. Adults would have received little competition from small theropods such as the small tyrannosaurid Alioramus, troodontids (Borogovia, Tochisaurus, Zanabazar), oviraptorosaurs (Elmisaurus, Nemegtomaia, Rinchenia) or Bagaraatan, sometimes considered a basal tyrannosauroid. Other theropods, like the gigantic Therizinosaurus, might have been herbivorous, and ornithomimosaurs such as Anserimimus, Gallimimus, and gigantic Deinocheirus might have been omnivores that only took small prey and were therefore no competition for Tarbosaurus.
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An ostrich walking on a road in Etosha National Park, Namibia As a hugely diverse group of animals, the posture adopted by theropods likely varied considerably between various lineages through time. All known theropods are known to be bipedal, with the forelimbs reduced in length and specialized for a wide variety of tasks (see below). In modern birds, the body is typically held in a somewhat upright position, with the upper leg (femur) held parallel to the spine and with the forward force of locomotion generated at the knee. Scientists are not certain how far back in the theropod family tree this type of posture and locomotion extends.
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Barsbold found that segnosaurids were so peculiar compared to more typical theropods that they were either a very significant deviation in theropod evolution, or were possibly outside the group; he nevertheless retained them within Theropoda. Later in 1983, Barsbold stated the segnosaurian pelvis deviated significantly from the theropod norm and found the configuration of their ilia generally similar to those of sauropods. Outdated restoration of a prosauropod-like, quadrupedal Erlikosaurus. "Segnosaurs" were often depicted this way until they were definitively identified as theropods. Gregory S. Paul concluded in 1984 that segnosaurs had no theropodan features but were derived, late-surviving Cretaceous prosauropods with adaptations similar to those of ornithischians.
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Lisbonne: Direction des Travaux géologiques du Portugal, 46p However, the spinosaurid nature of Suchosaurus was not recognized until a 1998 redescription of Baryonyx.Milner, A., 2003, "Fish-eating theropods: A short review of the systematics, biology and palaeobiogeography of spinosaurs". In: Huerta Hurtado and Torcida Fernandez-Baldor (eds.).
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Despite the huge reduction in size, no taxa in Ceratosauria ever lost a digit or any critical elements of the forelimb. Some joint variation has also been observed in Ceratosauria, and it has been postulated that they may have had better shoulder mobility than other large theropods.
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In the basic-type and morphotype scheme for eggshell classification (which is now typically disusedZelenitsky, D. K., and Therrien, F. (2008). "Phylogenetic analysis of reproductive traits of maniraptoran theropods and its implications for egg parataxonomy." Palaeontology, 51(4): 807–816.Grellet-Tinner, G., and Norell, M. (2002).
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It also lived alongside the theropods Kryptops, Suchomimus, Eocarcharia, and Afromimus. Crocodylomorphs like Sarcosuchus, Anatosuchus, Araripesuchus, and Stolokrosuchus also lived there. In addition, remains of a pterosaur, chelonians, fish, a hybodont shark, and freshwater bivalves have been found. Grass did not evolve until the late Cretaceous.
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The scientific memoirs of Thomas Henry Huxley. 4 vols and supplement, London: Macmillan. In 1896, Othniel Marsh recognized the fossil as a true member of the Dinosauria. John Ostrom thoroughly redescribed the species in 1978, making it one of the best-known small theropods at that time.
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Many larger theropods had skin covered in small, bumpy scales. In some species, these were interspersed with larger scales with bony cores, or osteoderms. This type of skin is best known in the ceratosaur Carnotaurus, which has been preserved with extensive skin impressions.Bonaparte, Novas, and Coria (1990).
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Pellegrinisaurus was unearthed from the Allen Formation, in which it probably lived alongside other titanosaurs, such as Aeolosaurus and Rocasaurus. Salgado suggested that contemporaneous hadrosaurids and the titanosaur Aeolosaurus inhabited coastal lowlands while other larger titanosaurs (such as Pellegrinisaurus) and theropods inhabited interior environments of the region.
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Gauthier, J. & Rowe, T. (1990). Ceratosauria. In The Dinosauria, Dodson et al (eds.). The femur of Protoavis is astonishingly similar to non-tetanurans, namely coelophysoids. The proximal femur displays a trochanteric shelf caudal to the lesser and greater trochanters, a feature distinguishing non-tetanurans theropods from Tetanurae.
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A morphometric analysis by López-Martínez and Vicens in 2012 found that it was an intermediate shape between avian and non- avian theropods, and also very similar to an enantiornithine egg from the Bajo de la Carpa Formation in Argentina, though their microstructures are quite different.
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AMERICAN MUSEUM NOVITATES, Number 3651, NEW YORK, NY 10024 35 pp., 17 figures June 25, 2009 Incisivosaurus is assumed to have been feathered like most other maniraptoran theropods. Its total body length has been estimated at and its weight at 2-4.6 kg (4.4-10 lbs).
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A vast majority of these senses were also well-developed in earlier coelurosaurs and other theropods, indicating that therizinosaurids inherited many of these traits from their small, carnivorous maniraptoran ancestors and retained the ancestral, carnivorous ear configuration to be used for their different and very specialized dietary purposes.
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Studies of the abelisaurid Majungasaurus indicate that it was a much slower-growing dinosaur than other theropods, taking nearly 20 years to reach adult size. Similar studies on other abelisaurid genera indicate that this slow maturation may have been a common trait to the whole of the Abelisauridae.
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Ornithomimids appear to have been preyed upon at least occasionally by other theropods, as evidenced by an ornithomimid tail vertebra that preserves tooth drag marks attributed to a dromaeosaurid (Saurornitholestes).Jacobsen, A.R. 2001. Tooth-marked small theropod bone: An extremely rare trace. p. 58-63. In: Mesozoic Vertebrate Life.
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"Last Patagonian theropods". In: Carpenter, K. 2005. The Carnivorous Dinosaurs, Indiana University Press, pp 153-160 However, in a 2004 abstract (and later a 2007 full paper), Rubén Juárez Valieri et al. concluded that Quilmesaurus, in view of the hatchet- shaped cnemial crest, was a member of the Abelisauridae.
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The smallest known ornithischian is Fruitadens haagarorum. The largest Fruitadens individuals reached just 65–75 cm. Previously, only carnivorous, saurischian theropods were known to reach such small sizes. At the other end of the spectrum, the largest known ornithischians reach about 15 meters (smaller than the largest saurischians).
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Metriacanthosaurus was a medium-sized theropod with a femur length of . Gregory S. Paul in 1988 estimated its weight at . Thomas Holtz gave a length of 8 meters (26.2 feet). Metriacanthosaurus was named for the height of its neural spines, which are actually not overly tall for theropods.
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The teeth belong to an animal the size of the dromaeosaurine Utahraptor, but they appear to belong to velociraptorines, judging by the shape of the teeth.Naish, D. Hutt, and Martill, D.M. (2001). "Saurischian dinosaurs: theropods." in Martill, D.M. and Naish, D. (eds). Dinosaurs of the Isle of Wight.
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Sue was mounted with forty-seven of such caudal vertebrae. The neck of T. rex formed a natural S-shaped curve like that of other theropods. Compared to these, it was exceptionally short, deep and muscular to support the massive head. The second vertebra, the axis, was especially short.
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Retrieved 28 February 2007. Dinosaur Valley State Park is located in Glen Rose Texas off 67 and 144 which is south west of Fort Worth. Dinosaur Valley State Park has some of the world's best preserved dinosaur tracks. The tracks were left by carnivorous theropods and herbivorous sauropods.
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This would make Spinosaurus the largest known carnivorous dinosaur. In 2019, the paleontologist W. Scott Persons and colleagues described a Tyrannosaurus specimen (nicknamed "Scotty"), and estimated it to be more massive than other giant theropods, but cautioned that the femoral proportions of the carcharodontosaurids Giganotosaurus and Tyrannotitan indicated a body mass larger than other adult Tyrannosaurus. They noted that these theropods were known by far fewer specimens than Tyrannosaurus, and that future finds may reveal specimens larger than "Scotty", as indicated by the large Giganotosaurus dentary. While "Scotty" had the greatest femoral circumference, the femoral length of Giganotosaurus was about 10% longer, but the authors stated it was a difficult to compare proportions between large theropod clades.
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They rejected the hypothesis by James Orville Farlow that the risk of injuries involved in such large animals falling while on a run, would limit the speed of large theropods. Instead they posed that the imbalance caused by increasing velocity would be the limiting factor. Calculating the time it would take for a leg to gain balance after the retraction of the opposite leg, they found the upper kinematic limit of the running speed to be . They also found comparison between the running capability of Giganotosaurus and birds like the ostrich based on the strength of their leg-bones to be of limited value, since theropods, unlike birds, had heavy tails to counterbalance their weight.
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The lower jaw did not have a coronoid process or a supradentary bone, the lack of which is a common feature of beaked theropods (ornithomimosaurs, oviraptorosaurs, therizinosaurs and birds), but unusual among theropods in general. The jaws of Gallimimus were edentulous (toothless), and the front part would have been covered in a keratinous rhamphotheca (horny beak) in life. The beak may have covered a smaller area than in North American relatives, based on the lack of nourishing foramina on the maxilla. The inner side of the beak had small, tightly packed and evenly spaced columnar structures (their exact nature is debated), which were longest at the front and shortening towards the back.
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Illustration of known material of U. comahuensis In 1996 in the Neuquén province of Argentina a skeleton of a theropod was discovered in the Sierra del Portezuelo and reported the same year.F.E. Novas, G. Cladera, and P. Puerta, 1996, "New theropods from the Late Cretaceous of Patagonia", Journal of Vertebrate Paleontology 16(3, suppl.):56A In 1997 Fernando Emilio Novas and Pablo Puerta named and described Unenlagia comahuensis. The generic name is derived from Mapuche uñùm, 'bird', and llag, 'half', in reference to the fact that the describers considered the species to be a link between birds and more basal theropods. The specific name refers to the Comahue, the region the find was made.
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Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventually became a wastebasket taxon. This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen's 1976 monograph. Major publications using the name "Megalosauridae" instead of "Allosauridae" include Gilmore, 1920, von Huene, 1926, Romer, 1956 and 1966, Steel, 1970, and Walker, 1964.
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Skeleton of Ornithomimus edmontonicus This timeline of ornithomimosaur research is a chronological listing of events in the history of paleontology focused on the ornithomimosaurs, a group of bird-like theropods popularly known as the ostrich dinosaurs. Although fragmentary, probable, ornithomimosaur fossils had been described as far back as the 1860s, the first ornithomimosaur to be recognized as belonging to a new family distinct from other theropods was Ornithomimus velox, described by Othniel Charles Marsh in 1890. Thus the ornithomimid ornithomimosaurs were one of the first major Mesozoic theropod groups to be recognized in the fossil record. The description of a second ornithomimosaur genus did not happen until nearly 30 years later, when Henry Fairfield Osborn described Struthiomimus in 1917.
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Because its fore and hindlimbs were preserved, Alxasaurus showed that Perle's assignment of segnosaurian hindlimbs to Therizinosaurus was probably correct. Russell and Dong, therefore, proposed that Segnosauridae was a junior synonym of the older name Therizinosauridae, and that Alxasaurus was the most completely known representative so far. They also named the new higher taxonomic rank Therizinosauroidea to contain Alxasaurus and Therizinosauridae because the new genus was somewhat different from its relatives. They concluded that therizinosaurs were tetanuran theropods, most closely related to ornithomimids, troodontids, and oviraptorids, which they placed together in the group Oviraptorosauria (because they found Maniraptora—the conventional grouping of these—invalid, and the higher-level taxonomy of theropods was in flux).
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Chinese and North American scientists described Caudipteryx and Protarchaeopteryx soon after. Based on skeletal features, these animals were non-avian dinosaurs, but their remains bore fully formed feathers closely resembling those of birds. "Archaeoraptor", described without peer review in a 1999 issue of National Geographic, turned out to be a smuggled forgery, but legitimate remains continue to pour out of the Yixian, both legally and illegally. Feathers or "protofeathers" have been found on a wide variety of theropods in the Yixian, and the discoveries of extremely bird-like non-avian dinosaurs, as well as non-avian dinosaur-like primitive birds, have almost entirely closed the morphological gap between non-avian theropods and birds.
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N. rumosus was most likely laid by some kind of non-avian maniraptor because of its similarities in microstructure and ornamentation to oviraptorosaur eggs and the eggs of Deinonychus. Other very small theropod eggs (ranging in size from to ), including Elongatoolithus, Prismatoolithus (and other indeterminate prismatoolithids), as well as ornithopod eggs assigned to Spheroolithus, are also known from the Kamitaki site. These eggs, along with skeletal remains, show that the parents of Nipponoolithus coexisted with numerous other small theropods, as well as an assemblage of ankylosaurs, titanosaurs, hadrosauroids, tyrannosaurs, and therizinosaurs. The parent of Nipponoolithus probably weighed roughly , comparable to the size of some contemporary small theropods from the Jehol biota in China.
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Decades of paleontological exploration in these deposits have uncovered only a few theropod dinosaur bones, so it appears that baurusuchids like Stratiotosuchus occupied the niche of top predators in the absence of these dinosaurs. A nearby Cretaceous deposit in Argentina called the Neuquén Group also contains baurusuchids, but they are much smaller than Stratiotosuchus and were likely out-competed by the wide range of theropod dinosaurs known from these deposits. In the absence of large theropods, carnivores like Stratiotosuchus may have fed on large herbivorous titanosaurs, including Adamantisaurus, Aeolosaurus, Gondwanatitan, and Maxakalisaurus. Pseudosuchians superficially resembling Stratiotosuchus were the top predators of the Triassic period, until they were decimated by the Triassic–Jurassic extinction event and replaced by large theropods.
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In 2011, Martinez et al. described Eodromaeus, a basal theropod from the same formation as Herrerasaurus. In a phylogenetic analysis, Eoraptor was placed within Sauropodomorpha, Herrerasauridae was placed as the most basal theropods, and Eodromaeus was placed as the next most basal. A more recent analysis, by Bittencourt et al.
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Theropods (spinosaurines), sauropods, and ornithischians have been reported from the Galve region. Fossil teeth belonging to baryonychines, allosauroids, dromaeosaurids and indeterminable coelurosaurs have also been recovered at some of the Galve sites. Those indeterminable coelurosaur teeth are from the Galve outcrops of the El Castellar Formation, and bear some avian resemblance.
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77 The other ten trackways were made by large theropods (footprint length more than ). The large theropod tracks are tri− and tetradactyl, mesaxonic, and have lengths and widths between and , respectively. Nearly all digit impressions possess claw marks, but they lack clear impressions of digital pads. The stride length varies between .
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Abelisaurids may have been ambush predators, using a bite-and-hold tactic to hunt large prey. The leg bones of Majungasaurus are comparatively short to other similarly-sized theropods, suggesting the dinosaur was comparatively slower–this same condition is seen in Rajasaurus. However, ceratosaurs may have been able to rapidly accelerate.
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Among theropods, two carcharodontosaurids (Carcharodontosaurus saharicus and Sauroniops pachytholus), one spinosaurid (Spinosaurus aegyptiacus), one coelurosaur (Deltadromeus agilis), an unnamed abelisaur and an unnamed dromaeosaur characterize the assemblage. Pterosaurs are also present, although their fossils are extremely rare and enigmatic: an azhdarchid, an ornithocheirid, a tapejarid and a pteranodontid are recognized.
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The classification of dinosaur eggs is based on the structure of the egg shells viewed in thin section via microscope, although new techniques such as electron backscatter diffraction have been used. There are three main categories of dinosaur eggs: spherulitic (sauropods and hadrosaurs), prismatic, and ornithoid (theropods, including modern birds).
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Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, a consensus of recent work suggests that they evolved from an early branch of maniraptoran theropods. Alvarezsaurids were highly specialized. They had tiny but stout forelimbs, with compact, bird-like hands.
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Tianyulong from China appears to preserve filamentous integument which has been interpreted to be a variant of the proto-feathers found in some theropods. These filaments include a crest along its tail. The presence of this filamentous integument has been used to suggest that both ornithischians and saurischians were endothermic.
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Lusotitan lived alongside species of the predatory theropods Allosaurus (A. europaeus), Ceratosaurus, Lourinhanosaurus, and Torvosaurus, the ankylosaurian Dracopelta, the sauropods Supersaurus, Lourinhasaurus, and Zby, and the stegosaurs Dacentrurus and Miragaia.Octávio Mateus. Late Jurassic dinosaurs from the Morrison Formation (USA) included the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania).
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"A review of European Triassic theropods." Gaia, 15: 75-88. Michael Benton, continuing the studies of the late Alick Walker redescribing the fossil in 2011, found it to be a dinosauriform more derived than Pseudolagosuchus and outside the smallest clade including Silesauridae and Dinosauria.Michael J. Benton and Alick D. Walker†. 2011.
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Bulletin of the American Museum of Natural History 371: 1–206. Most feathered dinosaurs discovered so far have been coelurosaurs. Philip J. Currie considers it likely and probable that all coelurosaurs were feathered. In the past, Coelurosauria was used to refer to all small theropods, but this classification has since abolished.
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Most pathologies preserved in theropod fossils are the remains of injuries, but infections and congenital deformities have also been documented. Pathologies are less frequently documented in small theropods, although this may simply be because the larger bones of correspondingly larger animals would be more likely to fossilize in the first place.
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Dinosaur bone fragments and more than 2,500 dinosaur footprints have been found in the park. They belong to biped and quadruped dinosaurs, theropods and sauropods from the Cretaceous period 120 million years ago. Llama Chaki, an archaeological site southeast of the town of Torotoro, has remnants of the Quechua culture.
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Dinosaurs that lived alongside Saurophaganax, and may have served as prey, included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus, and Othnielosaurus. Predators in this paleoenvironment included the theropods Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes, andFoster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.
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They resemble the type 3 feathers of theropods. The base plates are ordered in a hexagonal pattern but do not touch each other. The third type is unique. It was found on the upper lower legs and consists of bundles of six or seven ribbon-like structures, up to two centimetres long.
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The high- resolution mapping of the site from 1998 to 2015 revealed a total of 12,092 individual dinosaur tracks in 465 trackways. Nine different morphotypes of dinosaur tracks have been documented. Amongst them are several trackways of theropods, ornithopods, ankylosaurs and sauropods, with the latter group accounting for 26% of the trackways.
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154, no. 4, pp. 587-588. that have yielded a wide variety of examples of soft-tissue preservation (e.g., connective tissues in fishes and theropods or insect wings (2010): "A holistic approach to the palaeoecology of Las Hoyas Konservat-Lagerstätte (La Huérguina Formation, Lower Cretaceous, Iberian Ranges, Spain)", Journal of Iberian Geology, vol.
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It was closer to the coelophysids, including the well-known Coelophysis, than to Liliensternus. It has been assigned to the superfamily Coelophysoidea. An analysis of early dinosaurs by Baron, Norman and Barrett (2017) placed Lophostropheus in a position close to the derived theropods Sinosaurus and Cryolophosaurus.Baron, M.G., Norman, D.B., and Barrett, P.M. (2017).
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There is no evidence of feathers. Uniquely for theropods, there were osteoderms (knob-like skin bones) running along the sides of the neck, back and tail in irregular rows. Each bump showed a low ridge and measured in diameter. They were set apart from each other and became larger towards the animal's top.
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Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329. Other dinosaurs known from the Morrison include the theropods Koparion, Stokesosaurus, Ornitholestes, Allosaurus, and Torvosaurus; the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus; and the ornithischians Camptosaurus, Dryosaurus, Othnielia, Gargoyleosaurus, and Stegosaurus.
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During the Early Cretaceous, new dinosaurs evolved to replace the old ones. Sauropods were still present, but they were not as diverse as they were in the Jurassic Period. Theropods from the Early Cretaceous of North America include dromaeosaurids such as Deinonychus and Utahraptor, Acrocanthosaurus, and Microvenator. Sauropods included Astrodon, Brontomerus, and Sauroposeidon.
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The Quintaglio are a fictional species of sapient theropods which first appeared in Robert J. Sawyer's short story "Uphill Climb", and later on starred in his Quintaglio Ascension Trilogy. Descended from earth's dinosaurs, (specifically, Tyrannosaurs), they live on a moon orbiting a gas giant that they refer to as "The Face of God".
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Members of this group include the Dinosauromorpha, Pterosauromorpha, the genus Scleromochlus, and Aphanosauria. Dinosauromorpha contains more basal forms, including Lagerpeton and Marasuchus, as well as more derived forms, including dinosaurs. Birds belong to the dinosaurs as members of the theropods. Pterosauromorpha contains Pterosauria, which were the first vertebrates capable of true flight.
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The related Torosaurus, and the more distantly related diminutive Leptoceratops, were also present, though their remains have been rarely encountered. Theropods from these formations include genera of tyrannosaurids, ornithomimids, troodontids, avialans, caenagnathids, and dromaeosaurids. Acheroraptor and Dakotaraptor are dromaeosaurids from the Hell Creek Formation. Indeterminate dromaeosaurs are known from other fossil formations.
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Preserved skull bones of Panphagia protos (PVSJ 874) The teeth of Panphagia indicate a possible omnivorous diet, transitional in form between the mostly carnivorous theropods and the herbivorous sauropodomorphs. The teeth in the back of the jaw are shorter than those in the front, are leaf-shaped, and also have more marked serrations.
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Several of the arguments about whether similarities between birds and theropods are homologous that have been advanced by Feduccia have been particularly contentious. One example is identification of the digits of the avian and theropod hand, and whether, and if so by what mechanism, it might be possible to explain the discrepancy between the conflicting digital identities of tridactyl theropods and birds. Wagner and Gauthier proposed that a homeotic frame shift, whereby expression domains for groups of genes like the Hox d group, were repositioned during limb bud development, resulting in the development of the first, second, and third digits of the archosaur manus from what were originally condensations for the second, third, and fourth. This view has been supported by some other workers.
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There is significant evidence that birds emerged within theropod dinosaurs, specifically, that birds are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others. As more non-avian theropods that are closely related to birds are discovered, the formerly clear distinction between non-birds and birds becomes less so. This was noted already in the 19th century, with Thomas Huxley writing: > We have had to stretch the definition of the class of birds so as to include > birds with teeth and birds with paw-like fore limbs and long tails. There is > no evidence that Compsognathus possessed feathers; but, if it did, it would > be hard indeed to say whether it should be called a reptilian bird or an > avian reptile.
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The front teeth of the upper jaw were more robust than the rest, to provide an anchor point for the bite, while the low crown height of Majungasaurus teeth prevented them from breaking off during a struggle. Finally, unlike the teeth of Allosaurus and most other theropods, which were curved on both the front and back, abelisaurids like Majungasaurus had teeth curved on the front edge but straighter on the back (cutting) edge. This structure may have served to prevent slicing, and instead holding the teeth in place when biting. Examination of the teeth of Majungasaurus indicates that the theropod replaced its teeth anywhere from 2-13 times faster than other theropods, replacing the entire set within a span of two months.
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Head and neck of specimen FMNH PR 2836 Computed tomography, also known as CT scanning, of a complete Majungasaurus skull (FMNH PR 2100) allowed a rough reconstruction of its brain and inner ear structure. Overall, the brain was very small relative to body size, but otherwise similar to many other non- coelurosaurian theropods, with a very conservative form closer to modern crocodilians than to birds. One difference between Majungasaurus and other theropods was its smaller flocculus, a region of the cerebellum that helps to coordinate movements of the eye with movements of the head. This suggests that Majungasaurus and other abelisaurids like Indosaurus, which also had a small flocculus, did not rely on quick head movements to sight and capture prey.
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In 2008, French palaeontologist Romain Amiot and colleagues compared the oxygen isotope ratios of remains from theropod and sauropod dinosaurs, crocodilians, turtles and freshwater fish recovered from eight localities in northeastern Thailand. The study revealed that Siamosaurus teeth had isotope ratios closer to those of crocodilians and freshwater turtles than other theropods, and so it may have had semiaquatic habits similar to these animals, spending much of its daily life near or in water. Discrepancies between the ratios of sauropods, Siamosaurus, and other theropods also indicate these dinosaurs drank from different sources, whether river, pond or plant water. In 2010, Amiot and colleagues published another oxygen isotope study on turtle, crocodilian, spinosaurid, other theropod remains, this time including fossils from Thailand, China, England, Brazil, Tunisia, and Morocco.
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They interpreted the fact that histological data indicates some spinosaurids were more terrestrial than others as reflecting ecological niche partitioning among them. As some spinosaurids have smaller nostrils than others, their olfactory abilities were presumably lesser, as in modern piscivorous animals, and they may instead have used other senses (such as vision and mechanoreception) when hunting fish. Olfaction may have been more useful for spinosaurids that also fed on terrestrial prey, such as baryonychines. A 2018 study by the French palaeontologist Auguste Hassler and colleagues of calcium isotopes in the teeth of North African theropods found that spinosaurids had a mixed diet of fish and herbivorous dinosaurs, whereas the other theropods examined (abelisaurids and carcharodontosaurids) mainly fed on herbivorous dinosaurs.
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In the same article, they named the new genus Erlikosaurus (known from a well-preserved skull and partial skeleton)—which they tentatively considered a segnosaurid—and reported a partial pelvis of an undetermined segnosaurian, both from the same formation as Segnosaurus. The specimens provided relatively complete data on this group; they were united by their opisthopubic pelvis, slender mandible, and the toothless front of their jaws. Barsbold and Perle stated that, though some of their features resembled those of ornithischians and sauropods, these similarities were superficial and distinct when examined in detail. While they were essentially different from other theropods—perhaps due to diverging from them relatively early—and warranted a new infraorder, they did show similarities with the theropods.
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He noted, similar to Marsh, noted the small predicted size of the organ, but also that it was significantly developed. A number of similarities to the brains of modern reptiles were noted. A 1905 diagram showing the small size of an Edmontosaurus annectens brain (bottom; alongside that of Triceratops horridus, top) commented on in early sources James Hopson investigated the encephalization quotients (EQs) of various dinosaurs in 1977 study. Three ornithopods for which brain endocasts had previously been produced – Camptosaurus, Iguanodon, and Anatosaurus (now known as Edmontosaurus annectens) – were investigated. It was found that they had relatively high EQs compared to many other dinosaurs (ranging from 0.8 to 1.5), comparable to that of carnosaurian theropods and of modern crocodilians, but far lower than that of coelurosaurian theropods.
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Giganotosaurus was probably the apex predator in its ecosystem. It shared its environment with herbivorous dinosaurs such as the titanosaurian sauropod Andesaurus, and the rebbachisaurid sauropods Limaysaurus and Nopcsaspondylus. Other theropods include the abelisaurid Ekrixinatosaurus, the dromaeosaurid Buitreraptor, and the alvarezsaurid Alnashetri. Other reptiles include the crocodyliform Araripesuchus, sphenodontians, snakes, and the turtle Prochelidella.
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Animals from other localities include the sauropods Lapparentosaurus and "Bothriospondylus" madagascariensis, and another sauropod based on teeth; theropods of the groups Abelisauridae, basal Ceratosauria, Coelurosauria, and possibly Tetanurae, along with tracks of the ichnogenus Kayentapus; thalattosuchian crocodyliforms; a mammal belonging to the Tribosphenida; plesiosaurs; and possibly ichthyosaurs. Silicified wood is also present in the strata.
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Nothronychus were bulky herbivorous theropods with wide, sloth- like hip (resembling that of the non-related ornithischians), four-toed feet with all four toes facing forward, elongated necks and prominent arms with sharp claws. Both species were similar in dimensions, in length and weighing approximately . N. graffami was slightly robust than N. mckinleyi though.
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Skull of Abelisaurus. Although skull proportions varied, abelisaurid skulls were generally very tall and very short in length. In Carnotaurus, for example, the skull was nearly as tall as it was long. The premaxilla in abelisaurids was very tall, so the front of the snout was blunt, not tapered as seen in many other theropods.
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Contrary to most other theropods, the top portion of the radius bears a backwards bow similar to that of the ulna. The hand bears three digits, typical of the Maniraptora, which respectively bear 2, 3, and 4 phalanges. The overall length of the hand is . Several distinguishing characteristics of Jianianhualong are found among the phalanges.
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Crystal Palace Park guided by Richard Owen presents Megalosaurus as a quadruped; modern reconstructions make it bipedal, like most theropods The first reconstruction was given by Buckland himself. He considered Megalosaurus to be a quadruped. He thought it was an "amphibian", i.e. an animal capable of both swimming in the sea and walking on land.
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The eye openings of Bajadasaurus were exposed in top view of the skull, possibly allowing the animal to look forwards while feeding. Bajadasaurus was discovered in sedimentary rocks of the Bajada Colorada Formation, and its environment resembled a braided river system. It shared its environment with other dinosaurs including the sauropod Leinkupal and different theropods.
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Anatomy, Ontogeny, and Phylogeny of Coelophysoid Theropods (PhD). University of Texas at Austin. Coelophysidae is part of the superfamily Coelophysoidea, which in turn is a subset of the larger Neotheropoda clade. As part of Coelophysoidea, Coelophysidae is often placed as sister to the Dilophosauridae family, however, the monophyly of this clade has often been disputed.
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Avulsion surfaces, histosols, carbonaceous fossil roots, and silicified wood all provide evidence of a low-lying forested landscape with poor drainage. Other dinosaurs from the same locality include the ornithopod Talenkauen, the theropods Orkoraptor and Austrocheirus, and the sauropod Dreadnoughtus. Non-dinosaurian fauna known from the formation include crocodilians, turtles, bony fish, and lamniform sharks.
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These dinosaur footprints were in fact claw marks, which suggest that this theropod was swimming near the surface of a river and just the tips of its toes and claws could touch the bottom. The tracks indicate a coordinated, left-right, left- right progression, which supports the proposition that theropods were well- coordinated swimmers.
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Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present. Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. (2004) 861 pp. .
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The reason for this is their environment, which is deep water near volcanic islands; therefore, these sediments are hard to get to, giving these coelacanths an 80 million year gap or ghost lineage. Another ghost lineage was that of the averostran theropods, a ghost lineage now reduced considerably due to the discovery of Tachiraptor.
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The upper arm bone, the humerus, was short but robust. It had a narrow upper end with an exceptionally rounded head. The lower arm bones, the ulna and radius, were straight elements, much shorter than the humerus. The second metacarpal was longer and wider than the first, whereas normally in theropods the opposite is true.
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The second event occurred before the middle Campanian, and involved a migration back into Asia from North America by a common ancestor of Prenocephale and Tylocephale. Two species originally reported to be pachycephalosaurs discovered outside this range, Yaverlandia bitholus of England and Majungatholus atopus of Madagascar, have recently been shown to actually be theropods.
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Along with other saurischian dinosaurs (such as theropods, including birds), sauropods had a system of air sacs, evidenced by indentations and hollow cavities in most of their vertebrae that had been invaded by them. Pneumatic, hollow bones are a characteristic feature of all sauropods.Wedel, M.J. (2009). "Evidence for bird-like air sacs in Saurischian dinosaurs".
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Crocodilians like Crocodylus niloticus or Crocodylus porosus show more extensive injuries than theropod dinosaurs and so may have been more aggressive with other members of the same species than theropods were. Ralph Molnar has speculated that depressed fractures on the feet may be a result of toe biting, a behavior common in modern parrots.
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An abundance of fossil leaves found at dozens of different sites indicates that the area was largely forested by small trees. Ankylosaurus shared its environment with other dinosaurs that included the ceratopsids Triceratops and Torosaurus, the hypsilophodont Thescelosaurus, the hadrosaurid Edmontosaurus, an indeterminate nodosaur, the pachycephalosaurian Pachycephalosaurus, and the theropods Struthiomimus, Ornithomimus, Pectinodon, and Tyrannosaurus.
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Ekrixinatosaurus ('explosion-born reptile') is a genus of abelisaurid theropod which lived approximately 100 to 97 million years ago during the Late Cretaceous period. Its fossils have been found in Argentina. Only one species is currently recognized, Ekrixinatosaurus novasi, from which the specific name honors of Dr. Fernando Novas for his contributions to the study of abelisaurid theropods.
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However, in 2012, Matthew Carrano found that Cryolophosaurus was a tetanuran, related to Sinosaurus, but unrelated to Dilophosaurus. Fossil pelvis of Cryolophosaurus. The loop at the widest part of the pubis is large compared to later theropods. The following family tree illustrates a synthesis of the relationships of the early theropod groups compiled by Hendrickx et al.
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Yandangornis is a genus of theropods (possibly avialans) from the Late Cretaceous. It lived 85 million years ago in what is now China. The type species, Y. longicaudus, was formally described by Cai and Zhou in 1999. The holotype specimen is a mostly complete skeleton in the collection of the Zhejiang Museum of Natural History, with accession number M1236.
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Thus, Cuff and Rayfield suggested that the skulls were not efficiently built to deal well with relatively large, struggling prey, but that spinosaurids may overcome prey simply by their size advantage, and not skull build.Cuff, Andrew R., and Emily J. Rayfield. 2013. “Feeding Mechanics in Spinosaurid Theropods and Extant Crocodilians.” PLOS ONE 8 (5): e65295. doi:10.1371/journal.pone.0065295.
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The sole amphibian known is Notobatrachus; turtles are represented by a distinct form that was named Condorchelys; mammals are known from a few genera, including Argentoconodon, Asfaltomylos, and Henosferus; multiple dinosaurs have been identified, including the sauropods Volkheimeria, Patagosaurus, and a potential third genus that is yet unnamed, and theropods include the related Piatnitzkysaurus and Condorraptor.
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This subtriangular inner ear configuration is present in Allosaurus, lizards, turtles, but not in birds. The semi-"circular" canals themselves were actually very linear, which explains the pointed silhouette. In life, the floccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in other non-avian theropods, birds, and pterosaurs.
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The Clarens Formation is also well known for its numerous preserved dinosaur trackways of both large and small theropods, and also of small ornithischian dinosaurs. Petrified wood fragments, rhizoliths, coprolites, and planolites burrows have also been found.Kitching, J.W., 1979. Preliminary report on a clutch of six dinosaurian eggs from the Upper Triassic Elliot Formation, Northern Orange Free State.
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The heterodont dentition of Eoraptor consists of both serrated, recurved teeth in the upper jaw, like the teeth of theropods, and leaf-shaped teeth in the lower jaw, like the teeth of basal sauropodomorphs. Eoraptor had 4 teeth in the premaxilla and 18 teeth in the maxilla, a dental formula not dissimilar to that of Herrerasaurus.
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For example, similar theropods, ornithopods and sauropods have been found in both the Tendaguru and the Morrison. This has important biogeographical implications. The Early Cretaceous in Africa is known primarily from the northern part of the continent, particularly Niger. Suchomimus, Elrhazosaurus, Rebbachisaurus, Nigersaurus, Kryptops, Nqwebasaurus, and Paranthodon are some of the Early Cretaceous dinosaurs known from Africa.
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This argument is no longer taken seriously, because theropods replaced their teeth quite rapidly. Ever since the first discovery of Tyrannosaurus most scientists have agreed that it was a predator, although like modern large predators it would have been happy to scavenge or steal another predator's kill if it had the opportunity.Dorey, M. (1997). Tyrannosaurus. Dinosaur Cards.
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In: Weishampel DB, Dodson P, Osmólska H, eds. The dinosauria, 2nd edn. Berkeley, CA: University of California Press, 71–110. It may in fact be the most basal coelurosaurian yet known, or may even be close to the common ancestor of the two groups; in any case, it represents one of the oldest definitive tetanuran theropods.
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The consensus view in contemporary palaeontology is that the flying theropods, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids and troodontids. Together, these form a group called Paraves. Some basal members of Deinonychosauria, such as Microraptor, have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small.
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The vertebrae, originally incorrectly identified as dorsals, are thirteen to fourteen centimetres long. These remains are today commonly considered to be indistinguishable from those of other theropods from the same formation. A cervical vertebra, four rib heads and a dorsal rib have also been assigned to Dryptosauroides (D .sp), but they may have belonged to a different theropod.
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Finally, in Europe, dromaeosaurids, rhabdodontid iguanodontians, nodosaurid ankylosaurians, and titanosaurian sauropods were prevalent. Flowering plants were greatly radiating, with the first grasses appearing by the end of the Cretaceous. Grinding hadrosaurids and shearing ceratopsians became extremely diverse across North America and Asia. Theropods were also radiating as herbivores or omnivores, with therizinosaurians and ornithomimosaurians becoming common.
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As an ankylosaurian, Priodontognathus would have been a slow quadrupedal herbivore, built low to the ground, and possessing armor as a protective feature against theropods and other carnivores. It was a rather small animal, a few metres long; if the Oxfordian date is correct this might be seen as a feature shared with all early nodosaurids.
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He also at this time provisionally referred to it the right tibia NHMUK R.186, which was identified by Naish et al. (2001) as belonging to a basal coelurosaurian like a compsognathid, and has recently been referred to Ornithomimosauria by Allain et al. (2014).Naish, D., Hutt, S., and Martill, D.M. (2001). Saurischian dinosaurs 2: theropods.
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Unlike most theropods, the front teeth of M. knopfleri projected forward instead of straight down. This unique dentition suggests that they had a specialized diet, perhaps including fish and other small prey. Other bones of the skeleton indicate that Masiakasaurus were bipedal, with much shorter forelimbs than hindlimbs. M. knopfleri reached an estimated adult body length of around .
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Along with much rarer ankylosaurians and pachycephalosaurs, all of these animals would have been prey for a diverse array of carnivorous theropods, including troodontids, dromaeosaurids, and caenagnathids. Adult Albertosaurus was the apex predator in this environment, with intermediate niches possibly filled by juvenile albertosaurs.Eberth, D.A., 1997, "Edmonton group". In: Currie, P.J., Padian, K. (Eds.), Encyclopedia of Dinosaurs.
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Holtz has come up with several new theories and hypotheses about the dinosaurs' classification. For example, he coined the terms Maniraptoriformes and Arctometatarsus. He also proposed two classification systems for theropods. The first is the clade Arctometatarsalia, made up of tyrannosauroids, ornithomimosaurs, and troodontids, because all of these coelurosaurs had pinched middle metatarsal bones in their feet.
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Nipponoolithus rumosus is known only from a handful of isolated eggshell fragments ranging from 0.36 to 0.53 mm in thickness, just barely larger than a chicken egg.Tanaka, K., Zelenitsky, D. K., Saegusa, H., Ikeda, T., DeBuhr, C. L., & Therrien, F. (2016). Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods. Cretaceous Research, 57, 350–363.
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According to Frankfurt and Chiappe (1999), the Lecho Formation is composed of reddish sandstones. The Lecho is part of the Upper/Late Cretaceous Balbuena Subgroup (Salta Group), which is a near-border stratigraphic unit of the Andean sedimentary basin. Fossils from this formation include the titanosaur Saltasaurus along with a variety of avian and non-avian theropods.
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This would have indicated the presence of septate lungs, ventilated by a hepatic-piston diaphragm, driven by the liver and a Musculus diaphragmaticus, which in the fossil was visibly attached to the pubes. Such a system would be an argument against the idea that birds, whose lungs are ventilated by air-sacs, are coelurosaurian theropods, and an indication theropods were cold-blooded. John Ruben's conclusions have, however, been questioned by some scientists, such as Lawrence Witmer, who claimed the study to be flawed. The 2011 study concluded that due to the fact that the liver had been preserved as a vague halo, representing body fluids that after death might have covered a larger surface than the organs they originated from, its exact dimensions and extent cannot be determined.
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Named by O.C. Marsh in 1890, the family Ornithomimidae was originally classified as a group of "megalosaurs" (a "wastebasket taxon" containing any medium to large sized theropod dinosaurs), but as more theropod diversity was uncovered, their true relationships to other theropods started to resolve, and they were moved to the Coelurosauria. Recognizing the distinctiveness of ornithomimids compared to other dinosaurs, Rinchen Barsbold placed ornithomimids within their own infraorder, Ornithomimosauria, in 1976. The contents of Ornithomimidae and Ornithomimosauria varied from author to author as cladistic definitions began to appear for the groups in the 1990s. In the early 1990s, prominent paleontologists such as Thomas R. Holtz, Jr. proposed a close relationship between theropods with an arctometatarsalian foot; that is, bipedal dinosaurs in which the upper foot bones were 'pinched' together, an adaptation for running.
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The authors concluded that spinosaurids, like modern crocodilians and hippopotamuses, spent much of their daily lives in water. The authors also suggested that semiaquatic habits and piscivory in spinosaurids can explain how spinosaurids coexisted with other large theropods: by feeding on different prey items and living in different habitats, the different types of theropods would have been out of direct competition. In 2018, an analysis was conducted on the partial tibia of an indeterminate spinosaurine from the early Albian, the bone was from a sub-adult between 7–13 m (22–42 ft) in length still growing moderately fast before its death. This specimen (LPP-PV-0042) was found in the Araripe Basin of Brazil and taken to the University of San Carlos for a CT Scan, where it revealed osteosclerosis (high bone density).
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Since the 1930s, Barnum Brown described that an unsubscribed species of Kritosaurus, the most likely candidate being Kritosaurus navajovius, had inhabited the late Maastrichtian Ojo Alamo Formation, the Javelina Formation in Texas and the El Picacho Formation, which was a flood plain type environment at the time of the Cretaceous. These fossils might be of an unknown species of hadrosaur or an undescribed specimen of Kritosaurus. This genus lived alongside numerous species of dinosaurs including the sauropod Alamosaurus, the ceratopsians Bravoceratops, Ojoceratops, Torosaurus and a possible species of Eotriceratops, hadrosaurs which included a possible species of Edmontosaurus annectens, Saurolophus and Gryposaurus and the armored nodosaur Glyptodontopelta. Theropods from this environment which included Tyrannosaurus, smaller theropods like a species of Troodon and Richardoestesia, the oviraptorid Ojoraptorsaurus, indeterminate ornithomimids and dromaeosaurs.
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In 1998, the palaeontologist Thomas R. Holtz and colleagues pointed out that the serrations on the teeth of troodontids were different from those of typical, carnivorous theropods in their large size and wide spacing, which is similar to the condition in herbivorous dinosaurs (including therizinosaurid theropods) and lizards rather than carnivorous dinosaurs. They suggested that this difference in coarseness may be related to the size and resistance of plant and meat fibres, and that troodontids may have been herbivorous or omnivorous. They also pointed out that some features that had been interpreted as predatory adaptations in troodontids were also found in herbivorous and omnivorous animals, such as primates and raccoons. In 2001, the palaeontologists Philip J. Currie and Dong Zhiming rejected the idea that troodontids could have been herbivorous.
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Diagram of Deinonychus (left) and Archaeopteryx (right) forelimbs illustrating wing-like posture Contrary to the way theropods have often been reconstructed in art and the popular media, the range of motion of theropod forelimbs was severely limited, especially compared with the forelimb dexterity of humans and other primates. Most notably, theropods and other bipedal saurischian dinosaurs (including the bipedal prosauropods) could not pronate their hands—that is, they could not rotate the forearm so that the palms faced the ground or backwards towards the legs. In humans, pronation is achieved by motion of the radius relative to the ulna (the two bones of the forearm). In saurischian dinosaurs, however, the end of the radius near the elbow was actually locked into a groove of the ulna, preventing any movement.
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Though no skull material has been discovered for Ostrafrikasaurus, it is known that spinosaurid skulls resembled those of crocodiles; they were long, low, narrow and expanded at their front ends into a terminal rosette-like shape, with a robust secondary palate on the roof of the mouth that made them more resistant to stress and bending. In contrast, the primitive and typical condition for theropods was a tall, broader and wedge-like snout with a less developed secondary palate. The skull adaptations of spinosaurids converged with those of crocodilians; early members of the latter group had skulls similar to typical non-avian (or non- bird) theropods, later developing elongated snouts, conical teeth, and secondary palates. These adaptations may have been the result of a dietary change from terrestrial prey to fish.
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He tentatively classified Segnosauridae as theropods, traditionally thought of as the "meat-eating" dinosaurs, pointing to similarities in the mandible and its front teeth. Using features of their humeri and hand claws, he distinguished Segnosauridae from the theropod families Deinocheiridae and Therizinosauridae, which were then only known from the genera Deinocheirus and Therizinosaurus, respectively, mainly represented by large forelimbs found in Mongolia. Later in 1979, Barsbold and Perle found the pelvic features of segnosaurids and dromaeosaurids were so different from those of "true" theropods that they should be separated into three taxa of the same rank, possibly at the level of infraorder within Saurischia, one of the two main divisions of dinosaurs—the other being Ornithischia. In 1980, Barsbold and Perle named the new theropod infraorder Segnosauria, containing only Segnosauridae.
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The Dinosaur Discovery Museum in Kenosha, Wisconsin, United States, is dedicated to the exploration and explication of the relationship between modern birds and ancient carnivorous biped dinosaurs, the theropods, which include Carnotaurus, Tyrannosaurus rex, and Archaeopteryx. This link is especially well documented in the fossil record. The museum has the largest skeletal cast collection of theropods (meat-eating) dinosaurs in North America and is the only museum to focus a gallery specifically on the evolution of birds from non-avian dinosaurs, with a second smaller gallery focusing on "Little Clint", a three year old Tyrannosaurus uncovered by a dig conducted with the Carthage Institute of Paleontology. The museum is located in the former post office (later the home of the Kenosha Public Museum building) and is a part of the Kenosha Public Museums system.
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The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Barosaurus included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes andFoster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World.
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PaleoBios, 23(2): September 15, 2003. José Bonaparte and colleagues, in a 2007 study, found Saturnalia to be very similar to the primitive saurischian Guaibasaurus. Bonaparte placed the two in the same family, Guaibasauridae. Like Langer, Bonaparte found that these forms may have been primitive sauropodomorphs, or an assemblage of forms close to the common ancestor of the sauropodomorphs and theropods.
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The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Stokesosaurus included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Ornitholestes andFoster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World.
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In theropod dinosaurs, the antorbital fenestra is the largest opening in the skull. Systematically, the presence of the antorbital fenestra is considered a synapomorphy that unites tetanuran theropods as a clade. In contrast, most ornithischian dinosaurs reduce and even close their antorbital fenestrae such as in hadrosaurs and the dinosaur genus Protoceratops. This closure distinguishes Protoceratops from other ceratopsian dinosaurs.
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Additionally, Bernissartia sp., Lisboasaurus estesi, and Lusitanisuchus mitracostatus have also been found; the latter two were small, being less than in length, and likely also fed on insects like K. guimarotae. Dinosaurs from Guimarota are mainly known from teeth, and include a brachiosaurid, which is also rather small in size; theropods, including Stokesosaurus sp. (known from body fossils), Compsognathus sp.
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Cryolophosaurus restored with a speculative coat of feathers Classification of Cryolophosaurus is difficult because it has a mix of primitive and advanced characteristics. The femur has traits of early theropods, while the skull resembles much later species of the clade Tetanurae, like China's Sinraptor and Yangchuanosaurus. This led Paul Sereno et al. (1994) to place Cryolophosaurus in the taxon Allosauridae.
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Qiupalong is a genus of extinct ornithomimid theropods from the Late Cretaceous of what is now China and Canada. Life restoration The type specimen, holotype HGM 41HIII-0106, preserves partial hips and hindlimbs, and was named and described in 2011. The team describing it, Xu et al., found it to represent a new taxon, which they gave the binomial Qiupalong henanensis.
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Neuquensuchus shared its environment with a variety of animals, including snakes (Dinilysia), other crocodyliforms (Comahuesuchus, Cynodontosuchus, Notosuchus, and an unnamed form), and a variety of dinosaurs including abelisaurids, noasaurid (Velocisaurus), and alvarezsaurid (Alvarezsaurus) theropods, titanosaurians including Bonitasaura, and birds (Neuquenornis and Patagopteryx). Neuquensuchus, a small, slender crocodyliform, had limb proportions well-suited to running, and was probably a swift, land-living animal.
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In 2014, it was reported in the scientific literature that Sérgio Luis Simonatto with a team of the Museu de Paleontologia "Prof. Antonio Celso de Arruda Campos" had found the front of a theropod axis near São José do Rio Preto.Méndez A.H., Novas F.E., Iori F.V. 2014. "New record of abelisauroid theropods from the Bauru Group (Upper Cretaceous), São Paulo State, Brazil".
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Timothy Rowe, Richard A. Ketcham, Cambria Denison, Matthew Colbert, Xing Xu, Philip J. Currie, 2001, "Forensic palaeontology: The Archaeoraptor Forgery", Nature 410, 539 - 540 (29 Mar 2001), The scandal brought attention to illegal fossil deals conducted in China. Although "Archaeoraptor" was a forgery, many true examples of feathered dinosaurs have been found and demonstrate the evolutionary connection between birds and other theropods.
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For a long time, the precise relationships of Megalosaurus remained vague. It was seen as a "primitive" member of the Carnosauria, the group in which most large theropods were united.Carrano (2012) p. 266 In the late 20th century the new method of cladistics allowed for the first time to exactly calculate how closely various taxa were related to each other.
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The dorsal ribs were thick and curved yet hollow and pierced by a hole near their connection to the vertebrae. The gastralia (belly ribs) were wide and strongly built paddle-shaped structures, with the left and right sides fused at the midline of the chest. These features signified that megaraptorans were wide-bodied theropods, akin to the condition in tyrannosaurids.
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The close spatial proximity of skull elements (most belonging to Allosaurus) supports this hypothesis. Larger individual theropods almost certainly became mired while attempting to scavenge the carcasses of other entrapped dinosaurs (Richmond and Morris, 1996). However, some palaeontologists suggest that the mass deaths were in fact a result of a drought, and not a predator trap. Debates continue to this day.
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Tianyulong has a row of long, filamentous integumentary structures on the back, tail and neck of the specimen. The similarity of these structures with those found on some theropods suggests their homology with feathers and raises the possibility that the earliest dinosaurs and their ancestors were covered with homologous dermal filamentous structures that can be considered primitive feathers ("proto-feathers").
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Among the theropods, Allosaurus, Saurophaganax, Torvosaurus, Ceratosaurus, Coelurus, Ornitholestes, Tanycolagreus, Stokesosaurus, and Marshosaurus are found in the Morrison. An abundance of sauropods has been found there, including Apatosaurus, Diplodocus, Barosaurus, Brachiosaurus, Camarasaurus, Brontosaurus and Amphicoelias. Three genera of stegosaurs, Alcovasaurus, Stegosaurus and Hesperosaurus, have been found there. Finally, ornithopods found in the Morrison include Dryosaurus, Camptosaurus, Drinker, Othnielia, and Othnielosaurus.
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Theropods included the tyrannosaurs Albertosaurus, Gorgosaurus, Daspletosaurus, Teratophoneus, Bistahieversor, and Appalachiosaurus, and the dromaeosaurids Dromaeosaurus, Saurornitholestes, Atrociraptor, and Bambiraptor. Ceratopsians, such as Pachyrhinosaurus, Styracosaurus, Centrosaurus, Monoclonius, Brachyceratops and Pentaceratops also existed. Among hadrosaurs, Hypacrosaurus, Gryposaurus, Kritosaurus, Parasaurolophus, Corythosaurus, Lambeosaurus and Prosaurolophus existed. During the latest Cretaceous, the Maastrichtian age, the diversity of dinosaurs saw a decline from the preceding Campanian stage.
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Ischium Madsen originally was unsure about the phylogenetic position of Marshosaurus, placing it as Theropoda incertae sedis. Some later analyses showed Marshosaurus to be a member of Avetheropoda, a group of more bird-like theropods including Tyrannosaurus, Velociraptor and Allosaurus. However, Roger Benson (et al., 2009) found it to be a megalosauroid, using a lot of newly found characters of referred Megalosaurus specimens.
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Daemonosaurus is typically considered to be a basal theropod that lies outside the clade Neotheropoda,H.D. Sues, S. J. Nesbitt, D. S. Berman and A. C. Henrici. 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society B 278:3459-3464 a group that includes more advanced Triassic theropods (like Coelophysis) and their descendants.
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Daemonosaurus differs from Chindesaurus bryansmalli in features of the cervical vertebrae. A paper published by Baron et al. (2017) resurrected the clade Ornithoscelida to unite ornithischians and theropods to the exception of sauropodomorphs. Although not included in the original study, the authors added Daemonosaurus to their dataset after their hypothesis was criticized by a team of international researchers, Langer et al. (2017).
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The wrist had a version of the semilunate carpal also found in more derived theropods like maniraptorans. Of the three fingers, the innermost (or thumb) was the largest, and diverged from the others. The phalangeal formula is 2-3-4-0-0, meaning that the innermost finger (phalange) has two bones, the next has three, and the third finger has four.
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In Foreigner, a second species of sentient theropods is discovered on an archipelago on the other side of the world; they are simply known as "The Others". They are similar to the Quintaglios, but both genders have dewlaps, are yellow with grey highlights, and are smaller in stature. They can lie without physical changes, and have about 4 eggs each time.
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Coelophysids are characterized by slender, skinny builds and long, narrow skulls with large fenestrae to allow for a lighter skull. They are fairly primitive theropods, and so have fairly basal characteristics, such as hollow air sacs in the cervical vertebrae and obligate bipedalism. Their slender builds allowed them to be fast and agile runners. All known members of Coelophysidae are carnivores.
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Research by Matthew G. Baron, David B. Norman, and Paul M. Barrett in 2017 suggested a radical revision of dinosaurian systematics. Phylogenetic analysis by Baron et al. recovered the Ornithischia as being closer to the Theropoda than the Sauropodomorpha, as opposed to the traditional union of theropods with sauropodomorphs. They resurrected the clade Ornithoscelida to refer to the group containing Ornithischia and Theropoda.
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Contemporary dinosaurs were Kentrosaurus, various sauropods including Giraffatitan and Dicraeosaurus, and large theropods including Megalosaurus and Ceratosaurus. Pterosaurs are also common in the Tendaguru Formation, as well as mammaliaformes (ancestral to mammals). During the Jurassic, Tendaguru was part of the semi-arid coastline of Gondwana. Dysalotosaurus fossils were discovered in strata that were deposited in structures characteristic of tidal flats and lagoons.
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University of California Press:Berkeley 259-322. A 2010 overview of Late Jurassic sauropods from Dorset noted that Ischyrosaurus shared features seen in both Rebbachisauridae and Titanosauriformes, but lacked features to nail down its exact phylogenetic position.Paul M. Barrett, Roger B.J. Benson and Paul Upchurch (2010). "Dinosaurs of Dorset: Part II, the sauropod dinosaurs (Saurischia, Sauropoda) with additional comments on the theropods".
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Archosaurs developed into the well-known dinosaurs and pterosaurs, as well as the ancestors of crocodiles. Since reptiles, first rauisuchians and then dinosaurs, dominated the Mesozoic era, the interval is popularly known as the "Age of Reptiles". The dinosaurs also developed smaller forms, including the feather-bearing smaller theropods. In the Cretaceous period, these gave rise to the first true birds.
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Glut (1997), p. 645 In 1986, Jacques Gauthier redefined this and several other paleontological terms in a more rigorous fashion, based on cladistic methods. Tetanurae was defined as modern birds and all theropods more closely related to modern birds than to ceratosaurs, while Coelurosauria now comprised all members of Tetanurae more closely related to modern birds than to carnosaurs.Holtz et al.
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In 2017, DNHM D3012 was named as the type specimen of the new genus and species Liaoningvenator curriei by Shen Caizhi, Zhao Bo, Gao Chunling, Lü Junchang, and Martin Kundrát. The genus name Liaoningvenator combines Liaoning with the suffix -venator, meaning "hunter" in Latin; the specific name curriei honors the contributions of Canadian paleontologist Philip John Currie to the research of small theropods.
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Trigonoolithus is classified in the oofamily Prismatoolithidae, alongside Preprismatoolithus, Prismatoolithus, Protoceratopsidovum, Sankofa, and Spheruprismatoolithus. Moreno-Azanza et al. performed multiple cladistic analyses to determine the phylogenetic position of Trigonoolithus. Because no complete Trigonoolithus eggs are known, its position was slightly unstable, but Trigonoolithus was consistently placed as the basalmost member of Prismatoolithidae, or in a polytomy with other non- avian theropods and birds.
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Distribution of spinosaurids in Europe and North Africa during the Cretaceous; 1 is Baryonyx Spinosaurids appear to have been widespread from the Barremian to the Cenomanian stages of the Cretaceous period, about 130 to 95 million years ago, while the oldest known spinosaurid remains date to the Middle Jurassic. They shared features such as long, narrow, crocodile-like skulls; sub-circular teeth, with fine to no serrations; the terminal rosette of the snout; and a secondary palate that made them more resistant to torsion. In contrast, the primitive and typical condition for theropods was a tall, narrow snout with blade-like (ziphodont) teeth with serrated carinae. The skull adaptations of spinosaurids converged with those of crocodilians; early members of the latter group had skulls similar to typical theropods, later developing elongated snouts, conical teeth, and secondary palates.
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According to this scenario, the three fingers retained by tetanurans were therefore homologous (evolutionary corresponding to) with digit I, II, and III of basal theropods, which would have implications for the evolution of birds. alt=Diagram showing the evolution of the theropod hand However, the hypothesis of LDR is in contradiction to some embryological studies on birds which show that, from five developmental sites, the digits that develop are the three middle digits (II, III, IV). This inconsistency has been a matter of debate for almost 200 years, and has been used by paleornithologist Alan Feduccia to support the hypothesis that birds are descended not from theropods but from some other group of archosaurs which had lost the first and fifth digits. The mainstream view of bird origins among paleontologists is that birds are theropod dinosaurs.
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Distribution of spinosaurids in Europe and North Africa during the Cretaceous; 1 is Baryonyx Spinosaurids appear to have been widespread from the Barremian to the Cenomanian stages of the Cretaceous period, about 130 to 95 million years ago, while the oldest known spinosaurid remains date to the Middle Jurassic. They shared features such as long, narrow, crocodile-like skulls; sub-circular teeth, with fine to no serrations; the terminal rosette of the snout; and a secondary palate that made them more resistant to torsion. In contrast, the primitive and typical condition for theropods was a tall, narrow snout with blade-like (ziphodont) teeth with serrated carinae. The skull adaptations of spinosaurids converged with those of crocodilians; early members of the latter group had skulls similar to typical theropods, later developing elongated snouts, conical teeth, and secondary palates.
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They published the first ever cladogram showing the evolutionary relationships of Therizinosauria, and demonstrated that Beipiaosaurus had features of more basal theropods, coelurosaurs, and therizinosaurs. By the early 21st century, many more therizinosaur taxa had been discovered, including outside Asia (the first being Nothronychus from North America), as well as various basal taxa that helped understanding of the early evolution of the group (such as Falcarius, also form North America). Therizinosaurs were not considered as rare or aberrant anymore, but more diverse than previously thought (including in size), and their classification as maniraptoran theropods was generally accepted. The placement of Therizinosauria within Maniraptora continued to be unclear; in 2017, paleontologist Alan H. Turner and colleagues found them to group with oviraptorosaurs, while Zanno and collagues found them to be the most basal clade within Maniraptora in 2009, bracketed by Ornithomimosauria and Alvarezsauridae.
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Velaux-La Bastide Neuve represents a continental deposit. However, it was probably close to the shoreline, judging by the presence of claws from decapods, gastropods, and unionid mussels at the site. Fossils from the locality are well-preserved and were likely slowly transported. Other dinosaurs discovered at the site include the titanosaur Atsinganosaurus, in addition to teeth from nodosaurid ankylosaurs as well as neoceratosaurian and dromaeosaurid theropods.
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The teeth of the dentary were of similar shape and size, except for the first one, which was smaller. The teeth were compressed sideways, were oval in cross-section, and had serrations at the front and back borders, which is typical of theropods. The teeth were sigmoid- shaped when seen in front and back view. One tooth had nine to twelve serrations per mm (0.039 in).
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Montanoceratops shared the paleoenvironment of the St. Mary River Formation with other dinosaurs, such as the ceratopsians Anchiceratops and Pachyrhinosaurus canadensis, the armored nodosaur Edmontonia longiceps, the duckbilled hadrosaur Edmontosaurus regalis, the theropods Hagryphus, Saurornitholestes and Troodon, and the tyrannosaurid Albertosaurus which was likely the apex predator in its ecosystem."Alberta, Canada; 13. St. Mary River Formation," in Weishampel, et al. (2004). Pages 577-578.
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Journal of Vertebrate Paleontology 30 (Supplement 2): 55A. The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present. Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.
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Stokesosauridae is a suggested family of small to medium-sized tyrannosauroid theropods whose fossil remains have been found in North America and Europe. It includes the genera Stokesosaurus, and Juratyrant, and it may also include Eotyrannus.The family name first appeared in the supplemental info of Carr et al. (2017) and was first used within the main text of a paper during Wu et al.
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Through experimentation by Lauder and Pierce, the tail of Spinosaurus was found to have eight times as much forward thrust as the tails of terrestrial theropods like Coelophysis and Allosaurus, as well as being twice as efficient at achieving forward thrust. The discovery indicates that Spinosaurus may have had a lifestyle comparable to modern alligators and crocodiles, remaining in water for long periods of time while hunting.
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The first type consists of hair-like filaments covering the trunk, neck and head. These are up to three centimetres long and resemble the stage 1 "dino-fuzz" already known from theropods like Sinosauropteryx. The second type is represented by groups of six or seven downwards-projecting filaments up to 1.5 centimetres long, originating from a base plate. These are present on the upper arm and thigh.
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Indosuchus is a genus of abelisaurid dinosaur from the Late Cretaceous Period (70 to 66 million years ago – the Maastrichtian), a theropod related to Abelisaurus. Like most theropods, Indosuchus was a bipedal carnivore. It was about 7 metres long, weighed about 1.2 tonnes,Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 78 and had a crested skull, flattened on the top.
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The elaborate head crest of Guanlong, a basal tyrannosauroid from China. Bony crests are found on the skulls of many theropods, including numerous tyrannosauroids. The most elaborate is found in Guanlong, where the nasal bones support a single, large crest which runs along the midline of the skull from front to back. This crest was penetrated by several large foramina (openings) which reduced its weight.
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It also lived alongside the theropods Kryptops, Suchomimus, and Eocarcharia, and a yet-unnamed noasaurid. Crocodylomorphs like Sarcosuchus, Anatosuchus, Araripesuchus, and Stolokrosuchus also lived there. In addition, remains of a pterosaur, chelonians, fish, a hybodont shark, and freshwater bivalves have been found. Grass did not evolve until the late Cretaceous, making ferns, horsetails, and angiosperms (which had evolved by the middle Cretaceous) potential food for Nigersaurus.
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Diagram showing preserved portions of the skull compared to a human It is quite possibly the largest known member of Rauisuchia, with an estimated length of , even bigger than the prestosuchid Saurosuchus at in length. This would make Fasolasuchus the largest terrestrial predator to have ever existed save for large theropods. Like Saurosuchus, it had only a single row of caudal osteoderms, unusual among rauisuchians.Sulej, T. (2005).
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Other notable traits include the broad neural spines on the dorsal vertebrae. Life restoration Siats represents one of the largest known theropods from North America. Zanno and Mackovicky (2013), using other megaraptoran taxa as a proxy, estimated the length of the holotype individual at long, scaling upwards from the femur. Additionally, using a femur circumference regression, they estimated its mass at roughly 4 tons.
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For instance, the southeastern assemblage (which consists of the Carolinas and the Gulf Coast sites) has some tyrannosauroids such as Appalachiosaurus, some hadrosauroids such as Eotrachodon and Lophorhothon, nodosaurs, dromaeosaurs, and new leptoceratopsian while the northern assemblage (which consists of New Jersey, Delaware, and Maryland) has some tyrannosauroids such as Dryptosaurus, hadrosauroids such as Hadrosaurus, smaller theropods, and a possible lambeosaur in the area.
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Naish, D., Hutt S. and Martill, D., 2001, "Saurischian dinosaurs 2: Theropods". In: Martill D. and Naish D. (eds.), Dinosaurs of the Isle of Wight The Palaeontological Association, pp. 242-309 The front joint surface of the intercentrum of the axis, the second neck vertebra, is transversely widened. The odontoid process of the axis has small openings along the side edge of the front facet.
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In the foot, the outer side of the second metatarsal has a hollow surface to contact the third metatarsal. Estimated size based on the holotype Several traits that once were thought to be unique or apomorphic for Neovenator, subsequent research showed to have been shared by other theropods. The nostrils are large but not uncommonly so. Having pneumatised rear back vertebrae is normal for carcharodontosaurids.
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Some elongated eggs are symmetrical, whereas others have one rounded end and one pointed end (similar to bird eggs). Most elongated eggs were laid by theropods and have an avian-like eggshell, whereas the spherical eggs typically represent non-theropod dinosaurs. Diagram of a two- layered eggshell. Fossil dinosaur eggshells, like modern bird and reptile eggshells, are made up of calcium carbonate crystal units.
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The only specimens belonging to Megalosaurus bucklandii are from the Lower/Middle Bathonian of Oxfordshire and Gloucestershire. No material from outside of the Bathonian formations of England can be referred to Megalosaurus. It lived alongside the theropods Cruxicheiros, Iliosuchus and Streptospondylus, and the sauropods Cardiodon, Cetiosaurus, and possibly Cetiosauriscus. The pterosaur Rhamphocephalus, and indeterminate sauropod and ornithopod remains have also been found alongside fossils of Megalosaurus.
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Unlike many smaller fast-running dinosaurs, its femur was longer than its tibia and metatarsals, suggesting that Acrocanthosaurus was not a fast runner. Unsurprisingly, the hind leg bones of Acrocanthosaurus were proportionally more robust than its smaller relative Allosaurus. Its feet had four digits each, although as is typical for theropods, the first was much smaller than the rest and did not make contact with the ground.
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However, the rear part of the mandible (as seen in Murusraptor) was significantly more lightly built than that of tyrannosauroids. Preserved braincase material has similarities to both carcharodontosaurians and tyrannosauroids. The premaxillary teeth of Megaraptor were variably similar to those of tyrannosauroids, being small, incisiform (chisel-like) and D-shaped in cross section. However, Murusraptor's premaxillary teeth were fang-like, as in non-tyrannosauroid theropods.
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Anserimimus was recovered from the Nemegt Formation of Mongolia. The Nemegt is thought to represent alluvial plains containing meandering rivers. The layer Anserimimus was found, is dating from the early Maastrichtian stage of the Late Cretaceous, or about 70 million years ago. Aside from Gallimimus, other theropods found in the Nemegt Formation include the gigantic Tarbosaurus and Deinocheirus, as well as smaller dromaeosaurids, oviraptorosaurs, troodontids, and birds.
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's analysis placed Daemonosaurus as an ornithoscelidan outside the ornithichian-theropod split. This area was also occupied by Tawa and Chindesaurus. Although Daemonosaurus was not recovered as an ornithichian in any analysis, it also does not share any clear unambiguous characteristics exclusively with theropods. Though Nesbitt and Sues (2020) considered Daemonosaurus a likely saurischian, they were unable to conclusively place the genus within any subgroup of Dinosauria.
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Paleontologists now regard dinosaurs as being very intelligent for reptiles, but generally not as smart as their avian descendants. Some have speculated that if the Cretaceous–Paleogene extinction event had not occurred, the more intelligent forms of small theropods might have eventually evolved human-like levels of intelligence. Popular misconceptions of dinosaur neurology include the concept of a second brain in the pelvis of stegosaurs and sauropods.
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Eutyrannosauria is a clade of tyrannosauroid theropods whose distribution has been found in what is now Asia and North America. The clade consists of an evolutionary grade of tyrannosaurs such as Appalachiosaurus, Dryptosaurus, and Bistahieversor which led up to the family Tyrannosauridae. The group was named in 2018 by Delcourt and Grillo in their paper about possible southern hemisphere tyrannosauroids and the phylogeography of tyrannosaurs.
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Pterosaurs are known to have been eaten by theropods. In the 1 July 2004 edition of Nature, paleontologist Eric Buffetaut discusses an Early Cretaceous fossil of three cervical vertebrae of a pterosaur with the broken tooth of a spinosaur, most likely Irritator, embedded in it. The vertebrae are known not to have been eaten and exposed to digestion, as the joints are still articulated.
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Conifers were apparently the dominant canopy plants, with an understory of ferns, tree ferns, and angiosperms. Dinosaur Park is known for its diverse community of herbivores. As well as Stegoceras, the formation has also yielded fossils of the ceratopsians Centrosaurus, Styracosaurus and Chasmosaurus, the hadrosaurids Prosaurolophus, Lambeosaurus, Gryposaurus, Corythosaurus, and Parasaurolophus, and the ankylosaurs Edmontonia and Euoplocephalus. Theropods present include the tyrannosaurids Gorgosaurus and Daspletosaurus.
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Kayentavenator shared its paleoenvironment with other dinosaurs, such as several theropods including Dilophosaurus, Coelophysis kayentakatae, and the "Shake N Bake" theropod, the basal sauropodomorph Sarahsaurus,Rowe, T. B., Sues, H.-D., and Reisz, R. R. 2011. Dispersal and diversity in the earliest North American sauropodomorph dinosaurs, with a description of a new taxon. Proceedings of the Royal Society B: Biological Sciences 278(1708):1044–1053.
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The skull is lightly built with long and slender jaws and minute teeth. Shuvuuia is unique among non-avian theropods in the skull's ability to perform prokinesis, that is, it could flex its upper jaw independently of its braincase. The hindlimbs of Shuvuuia were long, slender, and short-toed, which may indicate significant running capabilities. The forelimbs, however, were unusually short and powerfully constructed.
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Rauhut & Carrano (2016) define Noasaurinae as "all noasaurids more closely related to Noasaurus than to Elaphrosaurus, Abelisaurus, Ceratosaurus, or Allosaurus". Masiakasaurus (and presumably other noasaurines) had a downturned lower jaw with long teeth splaying forwards. These teeth were spoon-shaped with sharply pointed tips and serrations along their outer edge. The rest of the teeth in the mouth were similar to the teeth of more conventional theropods.
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Diet is largely deduced by the tooth morphology, tooth marks on bones of the prey, and gut contents. Some theropods, such as Baryonyx, Lourinhanosaurus, ornithomimosaurs, and birds, are known to use gastroliths, or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are pachydont or phyllodont depending on the shape of the tooth or denticles.
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Accarie et al. assigned Genusaurus to the ceratosaur group of theropods, more precisely to the Coelophysoidea. A 2008 cladistic analysis by Carrano and Sampson placed Genusaurus in the Noasauridae along with Laevisuchus, Masiakasaurus, Noasaurus, and Velocisaurus; in turn, noasaurids are part of the Abelisauroidea group, which is part of the ceratosaur group. Subsequent phylogenetic analyses found Genusaurus to be a member of the Abelisauridae, specifically the Majungasaurinae.
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The arm is relatively short, equal to 60% of the hindlimb length. Especially the humerus is short, 42.1 millimetres long, with 60% of thighbone length, compared to a ratio of 100% with Anchiornis. The ulna is longer than the upper arm, a trait which in theropods is generally limited to flying birds. The ulna has a length of 47.2 millimetres and is only lightly bowed.
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Yunnan Publishing House of Science and Technology, Kunming, China 1–100. [Chinese] Kunmingosaurus wudingensis, Chinshakiangosaurus chunghoensis, Yunnanosaurus huangi, "Y." robustus, and an unnamed taxon; and the theropods Lukousaurus, Eshanosaurus, and Coelophysis sp. Changpeipus footprints have been found in the Lufeng Formation. In 2009, a study led by Li-Da Xing found that footprints from the Lufeng Formation were unique among ichnogenera, and named the footprints Changpeipus pareschequier.
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Later research by Sues et al. (2011) supports that Staurikosaurus and the related genus Herrerasaurus are theropods and evolved after the sauropod line had split from the Theropoda. Mortimer points out that Benedetto (1973) and Galton (1985) were the first to recognize that Staurikosaurus and Herrerasaurus were more closely related to each other than to sauropodomorphs or avepods, placing them both in the Herrerasauridae and Herrerasauria.Galton, 1985.
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Carpenter (2002) examined the bio-mechanics of theropods forelimbs and attempted to evaluate their usefulness in predation. He concluded that the forelimb of Coelophysis was flexible and had a good range of motion, but its bone structure suggested that it was comparatively weak. The "weak" forelimbs and small teeth in this genus, suggested that Coelophysis preyed upon animals that were substantially smaller than itself. Rinehart et al.
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Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), often called T. rex or colloquially T-Rex, is one of the most well-represented of the large theropods. Tyrannosaurus lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids.
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Size comparison of Elaphrosaurus with a human Elaphrosaurus was long and slender, with a long neck. What is known about Elaphrosaurus mostly comes from a single nearly complete skeleton and no skull has been found. It was distinctive among theropods for being short-legged for its length. Paul (1988) noted that this was the longest-bodied and shallowest-chested theropod that he had examined.
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Scale comparison of 3 Afrovenatorines Like other tetanurans, megalosaurids are carnivorous theropods characterized by large size and bipedalism. Specifically, megalosaurids exhibit especially giant size, with some members of the family weighing more than one tonne. Over time, there is evidence of size increase within the family. Basal megalosaurids from the Early Jurassic had smaller body size than those appearing in the late Middle Jurassic.
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In theropods, the head and neck are greatly pneumatized, and the forearms are reduced. This would help reduce the mass further away from the center of balance. This adjustment to the center of mass would allow the animal to reduce its rotational inertia, thereby increasing its agility. The sacral pneumaticity would lower its center of mass to a more ventral position, allowing it more stabilization.
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Indiana University Press. Hardbound: 634 pp. This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Nasutoceratops shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus.
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In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures in theropod dinosaurs. They found four toe bones from unidentifiable dromaeosaurids out of seventeen examined had stress fractures. Four of the twelve finger bones they also examined were likewise found to have stress fractures. Dromaeosaurids were the only theropods in Ralph Molar's 2001 survey to have pathologies of their claws.
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A Corythosaurus specimen has been preserved with its last meal in its chest cavity. Inside the cavity were remains of conifer needles, seeds, twigs, and fruits: Corythosaurus probably fed on all of these. The two species of Corythosaurus are both present in slightly different levels of the Dinosaur Park Formation. Both still co-existed with theropods and other ornithischians, like Daspletosaurus, Brachylophosaurus, Parasaurolophus, Scolosaurus, and Chasmosaurus.
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Elongatoolithus is an oogenus of dinosaur eggs found in the Late Cretaceous formations of China and Mongolia. Like other elongatoolithids, they were laid by small theropods (probably oviraptorosaurs), and were cared for and incubated by their parents until hatching. They are often found in nests arranged in multiple layers of concentric rings. As its name suggests, Elongatoolithus was a highly elongated form of egg.
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Judging from the stratigraphical, sedimentological and faunal data, the environment was thus probably semi-humid, possibly (seasonally?) semi-arid grassland or shrubland in a tropical or subtropical climate. The claystone apparently formed from sediment of a small floodplain, such as an ephemeral pool. A diverse fauna utilized the location as a habitat. Other theropods were plentiful, including Troodon (the nest of which was recovered), tyrannosaurids, and dromaeosaurids.
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Yurgovuchia compared to the fauna of the Yellow Cat Member from the Cedar Mountain Formation (Yurgovuchia in salmon) Other dinosaurs are also known from Don’s Place including the iguanodontians Iguanacolossus, polacanthines, and velociraptorine dromaeosaurids represented by a pubis (UMNH VP 21752) and a tentaive radius (UMNH VP 21751). Many additional theropods have previously been described from the Yellow Cat Member, including the therizinosaur Falcarius and the small, predatory troodontids Geminiraptor from the lower part of the member, in addition, the large dromaeosaurines Utahraptor, small ornithomimosaurs Nedcolbertia and unnamed eudromaeosaurs represented by a tail skeleton (UMNH VP 20209) from the upper part of the member. Yurgovuchia shared its environment and lived alongside other dinosaurs in the Lower Yellow Cat, such as the theropods Falcarius and Geminiraptor, the sauropods Mierasaurus and the large iguanodontians Iguanacolossus. There are also indeterminate goniopholidid crocodiles and the unnamed velociraptorines known from the Lower Yellow Cat.
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Dinosaurs include the theropods Megaraptor and Unenlagia (alongside dromaeosaurid and carcharodontosaurid teeth), the sauropod Futalognkosaurus, and indeterminate iguanodontian ornithopods. Additionally, a crocodylomorph similar to Comahuesuchus is also known from Futalognko, as are teeth of the Peirosauridae. Turtles of the group Pelomedusoidea have been found as well. Fish include a small member of the Euteleostei, two members of the Clupeomorpha, and a member of the Semionotidae, known from scales.
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22, no. 1-4, pp. 121–143. The Dry Mesa Quarry has produced the remains of the sauropods Apatosaurus, Diplodocus, Barosaurus, Supersaurus, Dystylosaurus and Camarasaurus, the iguanodonts Camptosaurus and Dryosaurus, and the theropods Allosaurus, Tanycolagreus, Koparion, Stokesosaurus, Ceratosaurus and Ornitholestes, as well as Othnielosaurus, Gargoyleosaurus and Stegosaurus. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers.
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Elements of the type specimen Prior to the discovery of Dryptosaurus in 1866, New World theropods were known only from some isolated theropod teeth discovered in Montana by Joseph Leidy in 1856.Leidy, J. 1856. Notice of remains of extinct reptiles and fishes discovered by Dr. F. V. Hayden in the badlands of the Judith River, Nebraska Territory. Proceedings of the Academy of Natural Sciences of Philadelphia 8: 72–73.
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The holotype shows eighteen teeth in the right dentary, seventeen in the left dentary; such an asymmetry is not rare among large theropods. A row of foramina is present below and on the outer side of the tooth row. These openings are relatively large below the first four teeth; more to behind, they become smaller and their row curves downwards. From the ninth tooth onwards, the foramina merge into a groove.
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Skeleton of Giganotosaurus, one of the largest theropods known. Tyrannosaurus was for many decades the largest and best known theropod to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus, Carcharodontosaurus, and Giganotosaurus. These large theropod dinosaurs rivaled or even exceeded Tyrannosaurus in size, though more recent studies show some indication that Tyrannosaurus, although shorter, was the heavier predator.
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On land, dinosaurs and other archosaurs staked their claim as the dominant race, with theropods such as Dilophosaurus at the top of the food chain. The first true crocodiles evolved, pushing the large amphibians to near extinction. All-in-all, archosaurs rose to rule the world. Meanwhile, the first true mammals evolved, remaining relatively small but spreading widely; the Jurassic Castorocauda, for example, had adaptations for swimming, digging and catching fish.
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The researchers concluded that the abundance of preserved plant material probably reflects the great abundance of local plant life during the Cretaceous. H97-04's excavation site Excavation A preserved shed teeth from theropods of differing size, champsosaur vertebrae, a fish scale, a pisidiid clam, and two unidentifiable coprolites in addition to its centrosaur fossils. The Excavation B site at H97-04 preserved a fish scale and two theropod teeth.
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Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation; in contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials. In the Mesozoic, some theropod dinosaurs such as Tyrannosaurus rex were probably obligate carnivores. Though the theropods were the larger carnivores, several carnivorous mammal groups were already present. Most notable are the gobiconodontids, the triconodontid Jugulator, the deltatheroideans and Cimolestes.
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Aerosteon, a Late Cretaceous allosaur, had the most bird-like air sacs found so far. Early sauropodomorphs, including the group traditionally called "prosauropods", may also have had air sacs. Although possible pneumatic indentations have been found in Plateosaurus and Thecodontosaurus, the indentations are very small. One study in 2007 concluded that prosauropods likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods).
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Teratophoneus curriei shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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The concept is now considered redundant, and the clade Bullatosauria is now viewed as synonymous with Maniraptoriformes. In 2002, Gregory S. Paul named an apomorphy-based clade Avepectora, defined to include all theropods with a bird-like arrangement of the pectoral bones, where the angled shoulder girdle (coracoids) come in contact with the breastbone (sternum). According to Paul, ornithomimosaurs are the most basal members of this group.Paul, G.S. (2002).
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The theropods Daspletosaurus and Troodon were also present. Both Maiasaura and Troodon are known to have formed nesting colonies in the area. Late Cretaceous fossil dinosaur footprints are surprisingly rare in Montana compared to other western states with contemporary deposits. This might be due to the local ancient environments not being well suited for track preservation or merely because scientists have not yet looked in the right places. Tyrannosaurus.
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Both Triassic amphibians and reptiles left behind footprints near what is now the Fall Creek Post Office. During the Late Jurassic deposition of the sediments now known as the Morrison Formation, both sauropods and theropods left behind footprints. Only two large tracksites of fossil footprints are known from the Morrison Formation and both of them are located in Colorado. A tracksite called Rancho del Rio preserves both sauropod and theropod tracks.
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However, there is general agreement that some behaviors which are common in crocodiles and birds, dinosaurs' closest living relatives, were also common among dinosaurs. Gregarious behavior was common in many dinosaur species. Dinosaurs may have congregated in herds for defense, for migratory purposes, or to provide protection for their young. There is evidence that many types of dinosaurs, including various theropods, sauropods, ankylosaurians, ornithopods, and ceratopsians, formed aggregations of immature individuals.
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Cross section of a typical theropod dinosaur tooth in side view. All dinosaur teeth possess the same tissue types but can differ in their appearance. Various major groups of dinosaurs have been examined through histology, these include the carnivorous theropods and herbivorous groups such as the sauropods, hadrosaurs and ceratopsians. Listed below are some of the dental anatomy that has been identified through histology and interpretations on their significance.
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The other paleofauna is from the Upper Yellow Cat, which includes: Aquatilavipes; Sauropods: Cedarosaurus and Moabosaurus; Iguanodontians: Cedrorestes and Hippodraco; Theropods: Martharaptor and Utahraptor; the nodosaurid Gastonia; Turtles: Glyptops and Trinitichelys; Fish: Ceratodus, Semionotus and indeterminate remains of Hybodontids and Polyacrodontids sharks. Lastly, the mammal Cifelliodon. Additional unnamed genera is known from this bed: U. Sail-backed Iguanodont, U. Eudromaeosaur and Velociraptorine, U. Goniopholidids, U. Mesoeucrocodylian and U. Neochoristodere.
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Such a trip would have required speeds of about , and could have brought it from Alaska to Alberta. The possible migratory nature of E. regalis contrasts with many other dinosaurs, such as theropods, sauropods, and ankylosaurians, which Bell and Snively found were more likely to have overwintered. In contrast to Bell and Snively, Anusuya Chinsamy and colleagues concluded from a study of bone microstructure that polar edmontosaurs overwintered.
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Ceratosauria's fortune changed in 1986 when Jacques Gauthier, in an attempt to clarify the evolution of birds, grouped the majority of theropods into either Ceratosauria or Tetanurae. In Ceratosauria, he placed the ceratosaurs and coelophysoids. Gauthier's paper brought Ceratosauria's use back in vogue, and by the early 1990s, Abelisaridae had also been included under Ceratosauria. The triumvirate model of ceratosaurs, coelophysoids, and abelisaurids would go unchallenged until the early 2000s.
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Ceratosaurs were theropods and thus carnivores, with one exception, Limusaurus inextricabilis was an herbivore with a toothless beak. Ceratosaurus has been argued to have eaten a large amount of fish and other aquatic creatures, though this has been disputed by many paleontologists. Tooth marks on large animals such as Allosaurus indicate that Ceratosaurus likely utilized scavenging often. The interesting jaws of the abelisaurids have drawn mixed dietary predictions.
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In all specimens, the tooth crowns of the upper jaws were exceptionally long. In specimen UMNH VP 5278, they measured up to in length, which is equal to the minimum height of the lower jaw. In the holotype, they are in length, which even surpasses the minimum height of the lower jaw. In other theropods, a comparable tooth length is only known from the possibly closely related Genyodectes.
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This formation is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania. The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Dryosaurus included the herbivorous ornithischians Camptosaurus, Stegosaurus and Nanosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes and Allosaurus.
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The radius is not unusual compared to other theropods. Megaraptorans also had very characteristic hands. The first two fingers were large and slender, but the third one was small. These relative differences in finger length are somewhat similar to the case in tyrannosauroids and various other basal coelurosaurs, but the megaraptoran trend of forearm and finger enlargement is opposite to the trend towards forearm diminishment which characterizes advanced tyrannosauroids.
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Megaraptor retained a vestigial fourth metacarpal, the hand bone that would have connected to the fourth finger in early dinosaurs. This was a primitive feature lost by most other tetanurans. The first two fingers had absurdly large unguals (claws); in Megaraptor the first claw was larger than the entire ulna. Unlike the large unguals of many other theropods (megalosauroids, for example), megaraptoran claws were thin and oval-shaped in cross-section.
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In non-coelurosaur theropods, the greater trochanter is small, making the femur teardrop-shaped when seen from above. The femoral head is slightly upturned as in carcharodontosaurians (particularly carcharodontosaurids) and some coelurosaurs. In megaraptorans, the portion of the femur near the knee is asymmetrical when seen from the front due to the lateral condyle projecting further distally than the medial condyle. The tibia was also similar to that of coelurosaurs.
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Foot finger bones Several bones of the left foot are preserved. The first metatarsal thins towards the ankle, similar to most theropods but unlike therizinosaurids, indicating that the first toe did not contact the ground. In conjunction with this, the claw of the first toe is smaller than those of the other toes. On the other hand, the toe claws are all deep and curved, as in other therizinosauroids.
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In 1984, Yuri Bolotsky and the Amur Complex Integrated Research Institute discovered a large dinosaur bonebed at Blagoveschensk. Most of the remains were of Amurosaurus (a lambeosaurine hadrosaur), but some came from turtles, crocodilians, theropods, nodosaurids, and a new hadrosaurine. For the hadrosaurine, cranial material (holotype AENM 1/319, braincase, plus others) was distinctive enough to permit the naming of a new genus. Kerberosaurus manakini would be described twenty years later.
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Institute "Juan Valdez", Cuenca, Argentina 126-163 Recognizing the difference between ornithomimids and other theropods, Rinchen Barsbold placed ornithomimids within their own infraorder, Ornithomimosauria, in 1976.R. Barsbold. 1976. K evolyutsii i sistematike pozdnemezozoyskikh khishchnykh dinozavrov [The evolution and systematics of late Mesozoic carnivorous dinosaurs]. In N. N. Kramarenko, B. Luvsandansan, Y. I. Voronin, R. Barsbold, A. K. Rozhdestvensky, B. A. Trofimov & V. Y. Reshetov (eds.), Paleontology and Biostratigraphy of Mongolia.
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Skeleton on display, Royal Tyrrell Museum of Paleontology The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Barosaurus, Diplodocus, Apatosaurus, Brontosaurus, and Brachiosaurus. Dinosaurs living alongside Camarasaurus included the herbivorous ornithischians Camptosaurus, Gargoyleosaurus, Dryosaurus, Stegosaurus, and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, Ornitholestes,Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World.
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Under the basic type and morphotype system of classification for fossil eggs, dictyoolithids are classified in an unnamed morphotype in the dinosauroid-spherulitic basic type. However, morphotypes and basic types are not normally used in modern research as they are often redundant and uninformative.Zelenitsky, D. K., and Therrien, F. (2008). "Phylogenetic analysis of reproductive traits of maniraptoran theropods and its implications for egg parataxonomy." Palaeontology, 51(4): 807–816.
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Carnotaurus is a genus of large theropod dinosaur that lived in South America during the Late Cretaceous period, between about 72 and 69.9 million years ago. The only species is Carnotaurus sastrei. Known from a single well- preserved skeleton, it is one of the best-understood theropods from the Southern Hemisphere. The skeleton, found in 1984, was uncovered in the Chubut Province of Argentina from rocks of the La Colonia Formation.
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Carnotaurus is a derived member of the Abelisauridae, a group of large theropods that occupied the large predatorial niche in the southern landmasses of Gondwana during the late Cretaceous. The phylogenetic relations of Carnotaurus are uncertain; it might have been closer to either Majungasaurus or Aucasaurus. Carnotaurus was a lightly built, bipedal predator, measuring in length and weighing at least . As a theropod, Carnotaurus was highly specialized and distinctive.
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The bumps probably represent clusters of condensed scutes, similar to those seen on the soft frill running along the body midline in hadrosaurid ("duck-billed") dinosaurs. Stephen Czerkas (1997) suggested that these structures may have protected the animal's sides while fighting members of the same species (conspecifics) and other theropods, arguing that similar structures can be found on the neck of the modern iguana where they provide limited protection in combat.
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Hagryphus shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, and the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, metatherians, and eutherians.
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Because of this, some paleontologists have suggested that dromaeosaurs are actually basal birds whose larger members are secondarily flightless, i.e. that dromaeosaurs evolved from birds and not the other way around. Evidence for this theory is currently inconclusive, but digs continue to unearth fossils (especially in China) of feathered dromaeosaurs. At any rate, it is fairly certain that flight utilizing feathered wings existed in the mid- Jurassic theropods.
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Life restoration of B. salgadoensis B. salgadoensis is seen as a terrestrial predator, living in a hot and arid climate. The position of the external nares was unsuited for an amphibious lifestyle like in modern crocodilians and the snout and teeth are laterally compressed like in theropods. Both of this supports the terrestrial hypothesis. The hot environment hypothesis is based on the lifestyle of modern crocodilians and the stratigraphy of Baurusuchus.
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The dorsal vertebrae were tall and narrow, with large pits known as pleurocoels on the side of their centra (spool-shaped main portion). These features are common in the vertebrae of large carnivorous theropods. Some of the vertebrae had fragments of bone in the pleurocoels, which were likely remnants of thin bony walls known as septa which divided the pits. Septa are also known in other megaraptorans and carcharodontosaurids.
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The neural arches of the vertebrae are taller and narrower in Tratayenia than in most other theropods. The tubular transverse processes (rib facets) project upwards and to the side. A large and deep excavation is located directly below each transverse process, bounded from the front and rear by thin laminae (ridges). The front edge is formed by the paradiapophyseal lamina and the rear edge is formed by the posterior centrodiapophyseal lamina.
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Poposauridae is a family of large carnivorous archosaurs which lived alongside dinosaurs during the Late Triassic. They were around long. Poposaurids are known from fossil remains from North and South America. While originally believed to be theropod dinosaurs (they mirrored the theropods in a number of respects, such as features of the skull and bipedal locomotion), cladistic analysis has shown them to be more closely related to crocodiles.
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A 2007 report described pathologies in the bones of Majungasaurus. Scientists examined the remains of at least 21 individuals and discovered four with noticeable pathologies. While pathology had been studied in large tetanuran theropods like allosaurids and tyrannosaurids, this was the first time an abelisauroid had been examined in this manner. No wounds were found on any skull elements, in contrast to tyrannosaurids where sometimes gruesome facial bites were common.
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Betasuchus is known only from a single incomplete femur, so its exact relationships with other theropods have been difficult to determine. In 1972 Dale Russell confirmed Von Huene's opinion that Betasuchus was an ornithomimosaurid, but also considered the name a nomen vanum: a failed emendation. Some workers in reference to the material still use M. bredai instead of Betasuchus. David Norman in 1990 listed Megalosaurus bredai as a nomen dubium.
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The lacrimal bone has a crest strongly projecting to above and sideways. In the lower jaw, the dentary is robust with the front tip higher than the middle section. In the pelvis, the ilium is short with a length less than half that of the femur (thighbone); in all other theropods the ilium is more than half as long. All these traits are unique within the clade Paraves.
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Segisaurus is significant because it demonstrates that the clavicle was primitively present in early theropods.Chure, D. J., and Madsen, J. H., 1996, The furcula in Allosaurid Theropods and its implication for determining bird origins: Journal of Vertebrate Paleontology, v. 16, supplement to n. 3, Abstracts of Papers, Fifty-sixth Annual Meeting, Society of Vertebrate Paleontology, American Museum of Natural History, New York, New York, October 16–19, p. 28A.
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According to the authors, this dramatic size range suggests the teeth are from individuals of different ages. Among theropods, this may also indicate size variation along the tooth row in the jaws, which is observed to have been prevalent in spinosaurids. The holotype tooth is relatively straight, with only minor front to back curvature. It is oval in cross section while other specimens are nearly circular in this aspect.
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Zupaysaurus was classified as the earliest known tetanuran theropod due to several features of its skull, dentition, and hindlimb. However, several features typical of more basal theropods were also noted by the original authors. Analyses by Carano (2005), Tykoski (2005), and Ezcurra and Novas (2005) have classified Zupaysaurus as a coelophysoid related to Segisaurus and probably Liliensternus, though more basal than Coelophysis.Carrano, M.T., Hutchinson, J.R., & Sampson, S.D. 2005.
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Coelophysis had an elongated snout with large fenestrae which helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced sigmoid curve. The braincase is known in Coelophysis bauri but little data could be derived because the skull was crushed. Unlike some other theropods, the cranial ornamentation of Coelophysis was not located at the top of its skull.
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Dromaeosaurid feeding was discovered to be typical of coelurosaurian theropods, with a characteristic "puncture and pull" feeding method. Studies of wear patterns on the teeth of dromaeosaurids by Angelica Torices et al. indicate that dromaeosaurid teeth share similar wear patterns to those seen in the Tyrannosauridae and Troodontidae. However, microwear on the teeth indicated that dromaeosaurids likely preferred larger prey items than the troodontids they often shared their environment with.
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The multiple clutches indicate that some therizinosaurs were colonial nesters, like hadrosaurs, prosauropods, titanosaurs, and birds, and the fact that they were found in a single stratigraphic layer suggests the dinosaurs nested at the site on a single occasion, and therefore did not exhibit site fidelity. The discovery was the first record of colonially nesting non-avian theropods from Asia, as well as the largest known non-avian theropod colony.
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These structures may have served as areas of interest for the smaller oviraptorosaurs. The dinosaur fauna of the Nemegt Formation was very diverse. Therizinosaurus shared its habitat with other theropods such as the deinonychosaurs Adasaurus and Zanabazar; ornithomimosaurs Anserimimus, Deinocheirus and Gallimimus; oviraptorosaurs Nemegtomaia, Elmisaurus, Gobiraptor, and the apex predator of the formation, Tarbosaurus. Other herbivorous dinosaurs include Barsboldia, Tarchia, Prenocephale, Nemegtosaurus, Opisthocoelicaudia and the most common herbivore, Saurolophus.
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Liliensternus is an extinct genus of basal neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. Liliensternus was a moderate-sized, bipedal, ground-dwelling carnivore, that could grow up to long. It is the best represented Triassic theropod from Europe and one of the largest known.Rauhut, O.M.W. & A. Hungerbuhler, 1998, "A review of European Triassic theropods".
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Holotype mount from the front Paul (1988) noted that Elaphrosaurus bambergi was too small to prey on the sauropods and stegosaurs present in its paleoenvironment, and instead, it likely hunted the small and swift ornithopod herbivores. However, newer studies support the idea that Elaphrosaurus was a herbivore or omnivore, owing to its close relation with Limusaurus and a neck which is much less flexible than those characteristic of carnivorous theropods.
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The Venenosaurus type specimen was found in the Early Cretaceous (Aptian-Albian) Poison Strip Member of the Cedar Mountain Formation in Grand County, Utah. The Denver Museum of Natural History opened a small Cedar Mountain Formation quarry in Eastern Utah. This quarry has produced diverse dinosaur fossils including sauropods, theropods, and ornithopods of varying states of growth. Of the sauropod remains from the quarry only one individual was fully grown.
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In addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the Cretaceous–Paleogene extinction event wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, alongside many species of theropods, crocodyliforms, and squamates (e.g., mosasaurs). Modern non- avian reptiles inhabit all the continents except Antarctica, although some birds are found on the periphery of Antarctica.
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Chilesaurus is an extinct genus of herbivorous dinosaur. The type and only species is Chilesaurus diegosuarezi. Chilesaurus lived about 145 million years ago (Mya) in the Late Jurassic period of Chile. Showing a combination of traits from theropods, ornithischians, and sauropodomorphs, this genus has far-reaching implications for the evolution of dinosaurs, such as whether the traditional saurischian-ornithischian split is superior or inferior to the newly proposed group Ornithoscelida.
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Syodon is characterized as a carnivore, likely feeding on small-bodied prey. They lack the ‘expansion of supraorbital bones over the orbits, which would act as a stress sink’ in certain hypercarniverous species such as thalattosuchian Dakosaurus. This thickened supraorbital regions also found in large theropods would have alleviated cranial stress used for feeding on large prey.Young, M. T., Brusatte, S. L., Ruta, M. & Andrade, M. B. 2010.
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The early sauropodomorphs were most likely omnivores as their shared common ancestor with the other saurischian lineage (the theropods) was a carnivore. Therefore, their evolution to herbivory went hand in hand with their increasing size and neck length. They also had large nostrils (nares), and retained a thumb (pollex) with a big claw, which may have been used for defense -- though their primary defensive adaptation was their extreme size.
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This slowing growth rate is the opposite of the general trend of sauropods and theropods, who reached greater sizes with increased growth rates. Some of the close relatives of Europasaurus represent the largest dinosaurs known, including Brachiosaurus and Sauroposeidon. Marpmann et al. (2014) proposed that the small size and reduced growth rate of Europasaurus was an effect of pedomorphism, where the adults of taxa retain juvenile characteristics, such as size.
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Prismatoolithids were previously hypothesized to be eggs of hypsilophodonts or ceratopsians, but later research found that they in fact are the eggs of theropods, based on analysis of preserved embryos of Prismatoolithus levis which showed them to be Troodon formosus. Therefore, Trigonoolithus was also probably laid by a theropod. Based on its phylogenetic position, Moreno-Azanza et al. concluded it was most likely a non-dromaeosaurian, non-oviraptorid coelurosaur theropod dinosaur.
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Based on the data in Snow et al. (1998). The original description of the fossils found its affinities unresolvable except that it was probably an ornithothoracine bird. Agnolin and Varricchio (2012) reinterpreted Piksi barbarulna as a pterosaur rather than a bird, most likely a member of Ornithocheiroidea. However, it has since been noted that the humerus of Piksi possesses features which found in some theropods but not in any pterodactyloid pterosaurs.
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Reconstructed brain of Erlikosaurus Erlikosaurus is poorly known from postcranial material, but the holotype skull became the focus of study in Computed Tomography (CT) scans that were published back in 2012 by the paleontologist Stephan Lautenschlager and Dr Emily Rayfield of Bristol University School of Earth Sciences, Professor Lindsay Zanno of the North Carolina Museum of Natural History and North Carolina State University, and Lawrence Witmer, Chang Professor of Paleontology at the Ohio University Heritage College of Osteopathic Medicine. Analysis of the brain cavity revealed that Erlikosaurus, and quite likely most other therizinosaurids, had well developed senses of smell, hearing, and balance, traits better associated with carnivorous theropods. The enlarged forebrain of Erlikosaurus may also have been useful in complex social behavior and predator evasion. These senses were also well-developed in earlier coelurosaurs and other theropods, indicating that therizinosaurs may have inherited many of these traits from their carnivorous ancestors and used them for their different and specialized dietary purposes.
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While discussing this hypothesis in 1976, both Alan Jack Charig and José Fernando Bonaparte pointed out that the saurischian pelvic shape is not a valid diagnostic new trait or synapomorphy but a basal character inherited from reptilian ancestors or symplesiomorphy, which suggested the possibility that the two main saurischian groups, the Theropoda and Sauropodomorpha, are not closely related. Bakker and Galton had based their analysis on a study of the basal sauropodomorph Anchisaurus, showing that it had many traits in common with the Ornithischia. Bakker now began to consider the possibility that, in view of the lack of proof for a close relationship between theropods and sauropodomorphs, the 1974 study indicated that Sauropodomorpha were more closely related to the ornithischian dinosaurs than to theropods. In 1986, Bakker openly proposed this in his book The Dinosaur Heresies: > Therefore all the plant-eating dinosaurs of every sort really constitute > one, single, natural group branching out from one ancestor, a primitive > anchisaurlike dinosaur.
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A 2018 study of buoyancy (through simulation with 3D models) by the Canadian palaeontologist Donald M. Henderson found that distantly related theropods floated as well as the tested spinosaurs, and instead supported they would have stayed by the shorelines or shallow water rather than being semi-aquatic. Spatial distribution of abelisaurids, carcharodontosaurids, and spinosaurids (the latter strongly associated with coastal environments) A 2010 study by the French palaeontologist Romain Amiot and colleagues proposed that spinosaurids were semiaquatic, based on the oxygen isotope composition of spinosaurid teeth from around the world compared with that of other theropods and extant animals. Spinosaurids probably spent much of the day in water, like crocodiles and hippopotamuses, and had a diet similar to the former; both were opportunistic predators. Since most spinosaurids do not appear to have anatomical adaptations for an aquatic lifestyle, the authors proposed that submersion in water was a means of thermoregulation similar to that of crocodiles and hippopotamuses.
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Right half of the holotype mandible shown from the inner side (A), the top (C), and bottom (D), and the left half shown from the inner side (B), compared with the mandibles of other therizinosaurs (to scale in lower right) The unusual features of therizinosaurs have led to several interpretations of their feeding behavior; there is no direct evidence of their diet, such as stomach contents and feeding traces. In 1970, Anatoly K. Rozhdestvensky suggested Therizinosaurus—the only member of the group known at the time—used its large claws to open termite mounds or gather fruits from trees. Barsbold and Perle pointed out in 1979 and 1980 that their peculiar features probably reflected a different evolutionary direction than those of more typical theropods, many of which were considered effective, active predators. Their delicate jaws, small, weak teeth and beaks, and short, compact feet indicated they would not have used the armaments of other theropods to procure food but could have preyed on fish.
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They also named the new higher taxonomic rank Therizinosauroidea to contain Alxasaurus and Therizinosauridae (since the new genus was somewhat different from its relatives), which they placed in the group Tetanurae within Theropoda. They considered therizinosaurs most closely related to ornithomimids, troodontids, and oviraptorids, which they placed together in the group Oviraptorosauria (since they found Maniraptora, the conventional grouping of these, invalid, and the higher level taxonomy of theropods was in flux at the time). basal therizinosaur Beipiaosaurus with impressions of feather structures, Paleozoological Museum of China The synonymy of Segnosauridae with Therizinosauridae was accepted by Perle himself and co-authors of a redescription of the holotype skull of Erlikosaurus in 1994, and they considered therizinosaurs maniraptoran theropods, the group that also includes modern birds (since they did find Maniraptora to be valid through their analysis). They also discussed the previous ornithischian and sauropod hypotheses for therizinosaur affinities in detail and demonstrated various faults with them.
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Size comparison of the native torvosaur (blue) and arriving theropod (green) Dinosaur footprints preserved at the Langenberg Quarry display a possible reason for the extinction of Europasaurus, and potentially other insular dwarfs present on the islands of the region. The footprints are located above the deposit of Europasaurus individuals, which shows that at least 35,000 years after that deposit there was a drop in sea level which allowed for a faunal overturn. The inhabiting theropods of the island, that coexisted with Europasaurus, would have been about , but the theropods that arrived over the land bridge preserve footprints up to , which indicates a body size between if reconstructed as an allosaurian. It was suggested by the describers of these tracks (Jens Lallensack and colleagues), that these theropod taxa likely made the specialized dwarf fauna extinct, and the bed from which the footprints originated (Langenberg bed 92) is probably the youngest in which Europasaurus is present.
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At Oarda de Jos A, crocodilian remains belonging to Allodaposuchus are very numerous; the area was probably "full of" them. Other crocodilians, such as Doratodon and Acynodon, were present in smaller numbers. Many bones found in the area exhibit bite marks, which they probably produced. Dinosaurs have also been found, including the ornithopods Telmatosaurus and Zalmoxes; titanosaurian sauropods; indeterminate dromaeosaurid theropods; and enantiornithine birds (including eggs), interpreted as representing a breeding colony.
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The hind limbs differed little from those of other ornithomimids, and were proportionally longer than in other theropods. The femur was nearly straight, long and slender, with a sideways flattened shaft. The tibia was straight, long, with two well developed condyles (rounded end of a bone) on the upper end and a flattened lower end. The fibula of the lower leg was flat, thin and broad at the upper end narrowing towards the lower end.
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The American Journal of Sciences and Arts 32:174-176 left by what was possibly an ornithopod, although due to the age of the tracks (some of which predate the oldest known ornithopod fossils), they were probably instead made by theropods. A 2.8 cm long footprint from the lower Jurassic represents the holotype.E. Hitchcock. 1845. An attempt to name, classify, and describe, the animals that made the fossil footmarks of New England.
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Saichania lived in a desert habitat, with sand dunes interspersed with oases. Other dinosaurs present in the Barun goyot included Lamaceratops, Bagaceratops and Tylocephale; large theropods have not been found yet. In the later Nemegt the gigantic predator Tarbosaurus was present. A study by William Gallagher in 1998 showed by means of a CAT-scan that specimen PIN 3142/250 had a healed puncture hole of a tyrannosauroid tooth above the right eye socket.
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The oofamily Dendroolithidae is often attributed to therizinosaur-grade dinosaurs. Some of the first dendroolithid eggs were found on the Bayan Shireh and Nanchao formations. Their relationships were confusing and obscure on the early years of research mainly because of the unusual traits among members. Several alternative classifications were proposed (such as the naming of Segnosauridae in 1979) until more complete specimens and other taxa were described during the 1990s, which confirmed them as theropods.
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Stress fractures to the hand are more likely to result from predatory behavior since injuries to the feet could be obtained while running or migrating. The researchers concluded that contact with struggling prey is the likely cause of a tendon avulsion found in the forelimb of the Tyrannosaurus specimen Sue. The authors concluded that the presence of stress fractures in theropods provide evidence for "very active" predation-based diets rather than obligate scavenging.
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This implies that it represents half of the snout-sacrum length, a value that is the highest for all known Mesozoic paravians. Within the Paraves, only some more recent birds have a proportionally longer neck. Among more basal theropods only some oviraptorosaurs approach this value; even ornithomimosaurs never surpass 40%. The length is not caused by a greater number of vertebrae, as in the Oviraptorosauria, but by an elongation of the individual vertebrae.
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Life restoration Pampadromaeus was a small bipedal animal. It shows a mosaic of basal and derived traits. It differs from other sauropodomorphs by a combination of characters. Some of these are shared with members of the Theropoda: the premaxilla is pointed downwards forming a subnarial gap with the maxilla and the anterior-most teeth are unserrated; in the location where with theropods the fenestra promaxillaris is positioned, a small depression is present.
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The pygostyle was rod-like as in Confuciusornis and Nomingia, but like in the former there was no long bony tail anymore. While the tarsometatarsi were more fused than in Archaeopteryx, the fibula was long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods like Avimimus). The first toe pointed backwards. In specimen IVPP V12375, the stomach contained numerous small gastroliths.
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The surangular bone has a deep oval excavation to the rear of its bone shelf and four rear surangular foramina, while other theropods possess at most two. A long narrow groove runs along the suture between the surangular and the prearticular bone. The notch in the suture between the articular and prearticular is pierced by a foramen. The front neck vertebrae possess an additional pneumatic foramen excavating the parapophysis, the lower rib contact.
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Evidence of early occupants of the area can be found in the dinosaur fossil tracks in the sandstone bedrock at Dinosaur Footprints Reservation to the east of Little Tom. Eubrontes giganteus, Anchisauripus sp., and Grallator cuneatus, all bipedal theropods, lived in this area some 200 million years ago. Although no fossil tracks are known to be visible on Little Tom, undoubtedly many are preserved deep within the sandstone layers on the property.
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The old, widely cited idea that all large dinosaurs, implicitly also Plateosaurus, swallowed gastroliths to digest food because of their relatively limited ability to deal with food orally has been refuted by a study on gastrolith abundance, weight, and surface structure in fossils compared to alligators and ostriches by Oliver Wings. The use of gastroliths for digestion seems to have developed on the line from basal theropods to birds, with a parallel development in Psittacosaurus.
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While paleontologists have long recognized the family Tyrannosauridae, its ancestry has been the subject of much debate. For most of the twentieth century, tyrannosaurids were commonly accepted as members of the Carnosauria, which included almost all large theropods. Within this group, the allosaurids were often considered to be ancestral to tyrannosaurids. In the early 1990s, cladistic analyses instead began to place tyrannosaurids into the Coelurosauria, echoing suggestions first published in the 1920s.
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Nothronychus were members of the Coelurosauria, the theropod group composed mainly by carnivorous dinosaurs. However, more specifically, Nothronychus form part of the sub-group Maniraptora, theropods which evolved into partial omnivores and, in the case of Nothronychus and their family, plant-eaters. Nothronychus mckinleyi was in 2001 assigned to the Therizinosauridae given the derived features of the genus. In 2010, Lindsay E. Zanno performed a large and comprehensive analysis of the Therizinosauria.
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The most basal theropods had five digits in the hand. Along the lineage that led to birds the number of digits in the hand decreased; by the emergence of the group Tetanurae, which includes birds, two digits had disappeared from the hand, leaving three. Traditionally, it has been hypothesized that the digits lost were the two outermost digits, i.e. digits IV and V, in a process known as Lateral Digit Reduction (LDR).
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Indiana University Press. pp. 327–329. Dinosaurs known from the Morrison include the theropods Ceratosaurus, Koparion, Stokesosaurus, Ornitholestes, Allosaurus and Torvosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Dryosaurus, Othnielia, Gargoyleosaurus and Stegosaurus. Diplodocus is commonly found at the same sites as Apatosaurus, Allosaurus, Camarasaurus, and Stegosaurus. Allosaurus accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web.
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Skorpiovenator's skull was short, stout and covered in the ridges, furrows, tubercles and bumpy nodules that are scattered over the heads of most abelisaurid theropods. It is craniocaudally short, similar to Carnotaurus, and is shorter and deeper than the skulls of Abelisaurus and Majungasaurus. Notably, the maxilla and lacrimal of Skorpiovenator are wider than in the corresponding bones of the remaining abelisaurids. Skorpiovenator had 19 maxillary teeth, which is more than any other known abelisaurid.
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The foot was also long, especially in the metatarsus. Like many other theropods of the Yixian Formation, Sinocalliopteryx was preserved with "protofeathers," simple filamentous integument (hairlike structures covering the skin), very similar to that found in Sinosauropteryx. The integument of Sinocalliopteryx differ in length across the body, with the longest protofeathers covering the hips, base of the tail, and back of the thighs. These longest protofeathers measured up to ten centimeters (4 in) in length.
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Little is known about Jurassic Texas, but there are fossil aquatic invertebrates of this age like ammonites in the state. During the Early Cretaceous local large sauropods and theropods left a great abundance of footprints. Later in the Cretaceous, the state was covered by the Western Interior Seaway and home to creatures like mosasaurs, plesiosaurs, and few icthyosaurs. Early Cenozoic Texas still contained areas covered in seawater where invertebrates and sharks lived.
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Although possible pneumatic indentations have been found in Plateosaurus and Thecodontosaurus, the indentations were very small. One study in 2007 concluded that basal sauropodomorphs like Massospondylus likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods). The study concluded that it was impossible to determine whether basal sauropodomorphs had a bird-like flow-through lung, but that the air sacs were almost certainly present.
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Orkoraptor is a genus of medium-sized theropod dinosaur from the late Cretaceous Period of Argentina. It is known from incomplete fossil remains including parts of the skull, teeth, tail vertebrae, and a partial tibia. The specialized teeth resemble those of some maniraptoriform theropods, namely the deinonychosaurs and compsognathids. This and other anatomical features led the authors who described it (Novas, Ezcurra, and Lecuona) to suggest that it was a maniraptoran coelurosaur.
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This idea is sometimes summarized as "you can't be your own grandmother". As paleontologist Peter Dodson pointed out: > I hasten to add that none of the known small theropods, including > Deinonychus, Dromaeosaurus, Velociraptor, Unenlagia, nor Sinosauropteryx, > Protarchaeopteryx, nor Caudipteryx is itself relevant to the origin of > birds; these are all Cretaceous fossils ... and as such can at best > represent only structural stages through which an avian ancestor may be > hypothezised to have passed.
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Appalachiosaurus ( ; "Appalachian lizard") is a genus of tyrannosauroid theropod dinosaur from the Late Cretaceous Period of eastern North America. Like almost all theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal over 7 meters (23 ft) long and weighing over 600 kilograms (1300 lb), which indicates an adult would have been even larger. It is the most completely known theropod from the eastern part of North America.
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The family was originally named by Raymond Martin Sternberg in 1940 as a family of flightless birds. The discovery of skeletons of the related oviraptorids revealed that they were in fact non- avian theropods, and the discovery of more complete caenagnathid remains revealed that Chirostenotes pergracilis, originally named on the basis of a pair of hands, and Citipes elegans, originally thought to be an ornithomimid, named from a foot, were caenagnathids as well.
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Many additional members of the Ceratosauria have been recognized since. The Ceratosauria split off early from the evolutionary line leading to modern birds, thus is considered basal within theropods. Ceratosauria itself contains a group of derived (nonbasal) members of the families Noasauridae and Abelisauridae, which are bracketed within the clade Abelisauroidea, as well as a number of basal members, such as Elaphrosaurus, Deltadromeus, and Ceratosaurus. The position of Ceratosaurus within basal ceratosaurians is under debate.
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It was clearly bipedal. Shortly afterwards, John Phillips created the first public display of a theropod skeleton in Oxford, arranging the known Megalosaurus bones, held by recesses in cardboard sheets, in a more or less natural position. During the 1870s, North American discoveries of large theropods, like Allosaurus, confirmed that they were bipedal. The Oxford University Museum of Natural History display contains most of the specimens from the original description by Buckland.
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Relative sizes of Acrocanthosaurus and a human Acrocanthosaurus was among the largest theropods known to exist. The largest known specimen (NCSM 14345) is estimated to have measured from snout to tail tip and weighed , with an upper maximum weight of within the realm of possibility for this specimen. Its skull alone was nearly in length. Skull diagram of NCSM 14345 The skull of Acrocanthosaurus, like most other allosauroids, was long, low and narrow.
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's arguments were formulated and published in a 2013 review of patagonian theropods, which removed Megaraptora from the Carcharodontosauria and instead placed the group within Coelurosauria. More specifically, megaraptorans were found to be deep within the Tyrannosauroidea, a radiation of basal coelurosaurs including the famed tyrannosaurids. As Novas et al. (2013) removed Megaraptora from Neovenatoridae, they named a new family, Megaraptoridae, which contained all Megaraptorans apart from the basal ("primitive") taxon Fukuiraptor.
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A nearly complete skeleton of Herrerasaurus ischigulastensis was discovered in the Ischigualasto Formation in San Juan, Argentina, in 1988. Less complete possible herrerasaurids have been found in North America, and they may have inhabited other continents as well. Herrerasaurid anatomy is unusual and specialized, and they are not considered to be ancestral to any later dinosaur group. They only superficially resemble theropods and often present a mixture of very primitive and derived traits.
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Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons.(published abstract only) There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including ceratopsians and hadrosaurs. However, only rarely are so many dinosaurian predators found at the same site. Small theropods like Deinonychus, Coelophysis and Megapnosaurus (Syntarsus rhodesiensis) have been found in aggregations, as have larger predators like Allosaurus and Mapusaurus.
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The Cretaceous unenlagiine Rahonavis also possesses features suggesting it was at least partially capable of powered flight. Although ornithischian (bird-hipped) dinosaurs share the same hip structure as birds, birds actually originated from the saurischian (lizard-hipped) dinosaurs if the dinosaurian origin theory is correct. They thus arrived at their hip structure condition independently. In fact, a bird-like hip structure also developed a third time among a peculiar group of theropods, the Therizinosauridae.
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Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons.(published abstract only) Model in RTM There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including ceratopsians and hadrosaurs. However, only rarely are so many dinosaurian predators found at the same site. Small theropods like Deinonychus and Coelophysis have been found in aggregations, as have larger predators like Allosaurus and Mapusaurus.
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This, along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods, suggests these niches may have been filled by juvenile tyrannosaurids. This is seen in modern Komodo dragons, where hatchlings start off as tree-dwelling insectivores and slowly mature into massive apex predators capable of taking down large vertebrates. For example, Albertosaurus have been found in aggregations that some have suggested to represent mixed-age packs.
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Sinosauropteryx was anatomically similar to Compsognathus, differing from its European relatives in its proportions. The skull of Sinosauropteryx was 15% longer than its thigh bones, unlike in Compsognathus, where the skull and thigh bones are approximately equivalent in length. The arms of Sinosauropteryx (humerus and radius) were only 30% the length of its legs (thigh bone and shin), compared to 40% in Compsognathus. Additionally, Sinosauropteryx had several features unique among all other theropods.
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They classified the genus as belonging to a new biological order, Sinosauropterygiformes, family Sinosauropterygidae, within the subclass Sauriurae. These proposals have not been accepted, and Sinosauropteryx is generally classified in the family Compsognathidae, a group of small-bodied long-tailed coelurosaurian theropods known from the Late Jurassic and Early Cretaceous of Asia, Europe, and South America. Below is a cladogram showing the placement of Sinosauropteryx within Coelurosauria by Senter et al. in 2012.
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Knoll, F. & Schoch, R., 2012, "CT scanning, rapid prototyping and re-examination of a partial skull of a basal crocodylomorph from the Late Triassic of Germany", Swiss Journal of Geosciences 105: 109-115 Oliver Rauhut and Axel Hungerbuhler (2000) noted features of the vertebrae which suggest that Procompsognathus may be a coelophysid or ceratosaur,Rauhut, O. and Hungerbuhler, A. (2000). "A review of European Triassic theropods." Gaia 15, 75-88 and Carrano et al.
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A phylogenetic analysis published along with the description of Lucianovenator assigned it to the Coelophysidae, in a clade with Coelophyis rhodesiensis and Camposaurus. This clade is supported by a single feature, the fact that the zygapophyses of the sacral vertebrae are fused. The authors of the paper suggested that the relative rarity of theropods in Rhaetian deposits compared to Norian deposits may be the result of taphonomic bias rather than a decline in diversity.
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The specimen they based it on (FMNH PR 2100) was not the largest one discovered. Larger specimens of Majungasaurus crenatissimus could have been similar in size to its relative Carnotaurus, which has been estimated to weigh . The skull of Majungasaurus is exceptionally well-known compared to most theropods and generally similar to that of other abelisaurids. Like other abelisaurid skulls, its length was proportionally short for its height, although not as short as in Carnotaurus.
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Specimens IVPP V57, IVPP V60 and IVPP V272 were collected by Young in blue mudstone from the same formation and were also assigned to Y. huangi. These specimens from the Shawan Member are also housed in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology. Yunnanosaurus huangi and Yunnanosaurus robustus shared their paleoenvironment with the ornithischians Bienosaurus, and Tatisaurus, the sauropodomorphs Gyposaurus, Lufengosaurus, and Jingshanosaurus, and the theropods Sinosaurus triassicus and Eshanosaurus.
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The morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey. The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite.
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The Mistaken Extinction: Dinosaur Evolution and the Origin of Birds. Freeman. While the roots of these various groups are found in the Middle Jurassic, they only became abundant during the Early Cretaceous. A few paleontologists, such as Gregory S. Paul, have suggested that some or all of these advanced theropods were actually descended from flying dinosaurs or proto-birds like Archaeopteryx that lost the ability to fly and returned to a terrestrial habitat.Paul, G.S. (2002).
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These fossils were discovered in the Candeleros Formation, the oldest formation within the Neuquén Group of Neuquén Province, Argentina. This formation dates to the Cenomanian stage of the Late Cretaceous period, about 99.6 to 97 million years ago. For the most part, the Candeleros represents an ancient braided river system, and besides Andesaurus, also contains fossils of theropods like Buitreraptor and the enormous Giganotosaurus, as well as other sauropods such as the rebbachisaurid Limaysaurus.
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Sarcosaurus (meaning "flesh lizard") is a genus of basal neotheropod dinosaur, roughly long. It lived during the Hettangian-Sinemurian boundary of the Early Jurassic, about 199-194 million years ago. Sarcosaurus is one of the earliest known Jurassic theropods, and one of only a handful of theropod genera from this time period. Along with Dracoraptor hanigani it is one of the two described neotheropods from the lowermost Jurassic of the United Kingdom.
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Early-Mid Jurassic (170 Ma) It is part of the Shemshak Group, a Late Triassic to Callovian set of coal bearing largely fluvo-lacustrine sediments up to 4000 metres thick located within the Alborz Mountains. The outcrop of sediments is strongly controlled by numerous fault structures in the region. The formation predominantly consists of sandstone, with subordinate siltstone and shale. Dinosaur tracks are known from the formation, including sauropods, and tridactlyl and didactyl theropods.
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Other dinosaurs from the Wessex Formation of the Isle of Wight include the theropods Neovenator, Aristosuchus, Thecocoelurus, Calamospondylus, and Ornithodesmus; the ornithopods Iguanodon, Hypsilophodon, and Valdosaurus; the sauropods Ornithopsis, Eucamerotus, and Chondrosteosaurus; and the ankylosaur Polacanthus. The Papo Seco Formation of Portugal where Baryonyx has possibly been identified is composed of marl, representing a lagoon environment. Other dinosaur remains from the area include fragments tentatively assigned to Mantellisaurus, a macronarian sauropod, and Megalosaurus.
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NOVITATES 2405; 1-39 Staurikosaurus lived during the late-Carnian and early-Norian stage, of the Late Triassic, approximately 225 million years ago—which makes it one of the earliest dinosaurs known. At long,Grillo, O.N. and Azevedo, S.A.K. (2011). "Recovering missing data: estimating position and size of caudal vertebrae in Staurikosaurus pricei Colbert, 1970." Annals of the Brazilian Academy of Sciences, tall, and weighing , Staurikosaurus was small in comparison to later theropods like Megalosaurus.
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Size of S. langstoni compared to a human Like other theropods in the Dromaeosauridae, Saurornitholestes had a long, curving, blade-like claw on the second toe. Saurornitholestes was more long-legged and lightly built than other dromaeosaurids such as Velociraptor and Dromaeosaurus. It resembles Velociraptor in having large, fanglike teeth in the front of the jaws. Saurornitholestes most closely resembles Velociraptor, although the precise relationships of the Dromaeosauridae are still relatively poorly understood.
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Restoration. Alvarezsaurus was a bipedal theropod. Like other lightweight theropods, it had a long tail, and its leg structure suggests that it was a fast runner. The most proximal elements of Alvarezsaurus caudal vertebrae exhibited ventrally sharp centra and the transerve processes of these vertebrae were sub-triangular and laterodistally directed, features seen in other alvarezsaurids like Shuvuuia. Spinal processes were entirely absent or poorly developed, and each caudal vertebra supported short prezygapophyses.
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The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present. Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press.
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Research on the olfactory bulbs has shown that T. rex had the most highly developed sense of smell of 21 sampled non-avian dinosaur species. Cast of the braincase at the Australian Museum, Sydney. Somewhat unusually among theropods, T. rex had a very long cochlea. The length of the cochlea is often related to hearing acuity, or at least the importance of hearing in behavior, implying that hearing was a particularly important sense to tyrannosaurs.
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Studies suggest that the paleoenvironment of the Tendaguru Formation was a marginal marine environment with both non-marine faunal and floral content. The Middle Dinosaur Member of the Tendaguru Formation has yielded the sauropods Giraffatitan, Australodocus, Janenschia, Tornieria and Dicraeosaurus, theropods similar to Allosaurus and Ceratosaurus, the carcharodontosaurid Veterupristisaurus, the stegosaurid Kentrosaurus and the iguanodontian Dysalotosaurus. Dinosaurs shared this paleoenvironment with pterosaurs like Pterodactylus and Rhamphorhynchus, as well as with early mammals.
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These two groups were named Coelurosauria and Pachypodosauria respectively. Later on, Huene distinguished between carnivorous and herbivorous dinosaurs in Pachypodosauria, placing the meat-eaters in a new group Carnosauria. As more information was uncovered about basal theropods and phylogenetic characteristics, modern paleontologists began to question the proper naming for this group. In 2005 paleontologist Paul Sereno rejected the use of the clade Megalosauridae due to its ambiguous early history in favor of the name Torvosauridae.
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Condorraptor is a genus of megalosauroid theropod dinosaur. Its genus name means 'robber from Cerro Condor', referencing a nearby village, while its species name, currumili, is named after Hipolito Currumil, the landowner and discoverer of the locality. It was among the earliest large South American theropods, having been found in Middle Jurassic strata of the Cañadón Asfalto Formation in the Cañadón Asfalto Basin of Argentina. The type species, described in 2005, is Condorraptor currumili.
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The Nanxiong Basin is known for its abundance of fossil eggs, predominantly the oviraptorisaurian eggs Elongatoolithus and Macroolithus. Other types of eggs include other elongatoolithids, as well as prismatoolithids, megaloolithids, and ovaloolithids. Footprints show that Nanxiong Basin was populated by ornithopods, theropods, and possibly sauropods. Southern China, particularly the Nanxiong Formation in Jiangxi Province, possibly has the greatest oviraptorosaur diversity in the world, and also includes several associations of oviraptorosaurs with Macroolithus or similar eggs.
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Archaeopteryx has historically been considered the first bird, or Urvogel. Although newer fossil discoveries filled the gap between theropods and Archaeopteryx, as well as the gap between Archaeopteryx and modern birds, phylogenetic taxonomists, in keeping with tradition, almost always use Archaeopteryx as a specifier to help define Aves. Aves has more rarely been defined as a crown group consisting only of modern birds. Nearly all palaeontologists regard birds as coelurosaurian theropod dinosaurs.
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The paleoenvironment of the Shishugou Formation was warm but had a basin-wide seasonal dry climate. The Wucaiwan locality of the Shishugou Formation has produced the remains of other theropods, such as the basal ceratosaur Limusaurus inextricabilis,Xu, X., Clark, J. M., Mo, J., Choiniere, J., Forster, C. A., Erickson, G. M., Hone, D. W. E., Sullivan, C., Eberth, D.A., Nesbitt, S., Zhao, Q., Hernandez, R., Jia, C.-K., Han, F.-l.&Guo;, Y. 2009a.
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These other theropods, however, were recovered in sediments that were Oxfordian in age. This rich paleofauna also included pterosaurs like Sericipterus, ornithischians like Jiangjunosaurus and Yinlong and the sauropods Bellusaurus, Klamelisaurus, Tienshanosaurus and Mamenchisaurus. Aorun was probably a predator of small lizards and mammals. Aorun is the seventh thropod, and oldest coelurosaur known from the Shishugou Formation, which is considered one of the most phylogenetically and trophically diverse middle to late Jurassic theropod faunas.
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With a fully erect stance, Stratiotosuchus has many features convergent with theropod dinosaurs, which are fully bipedal. In Stratiotosuchus, a roughly surfaced region on the upper part of the femur is analogous to the accessory trochanter common to tetanuran theropods. These projections are thought to have anchored the same muscle, called the puboischiofemoralis internus pars dorsalis. A crest on the forward edge of the tibia is similar to those seen in early theropod dinosaurs.
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The remains of Taurovenator were discovered in a layer of the Huincul Formation on the Violante Farm, southeast of the Ezequiel Ramos-Mexía Lake, Río Negro Province, Argentina, by Matías Motta in 2005. Taurovenator was found alongside the megaraptoran Aoniraptor and indeterminate remains of other Carcharodontosauridae, as well as abelisauroids and Paraves. This diverse assemblage of theropods was part of the Huincul Formation in Neuquén Province. They shared this environment with Mapusaurus, Argentinosaurus, Skorpiovenator and Ilokelesia.
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The distribution of the three major groups of dinosaurs – the theropods, sauropods, and ornithischians – was similar that of the crocodiles. East Asia remained isolated with endemic species including psittacosaurs (horned dinosaurs) and Ankylosauridae (club-tailed, armoured dinosaurs). In the early Eocene a peak in global warming led to a pan-Arctic fauna with alligators and amphibians present north of the Arctic Circle. In the early Palaeogene, landbridges still connected continents, allowing land animals to migrate between them.
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Specimens such as Sue and Scotty are both estimated to be the most massive theropods known to science. There is still no clear explanation for exactly why these animals grew so much larger than the land predators that came before and after them. The largest extant theropod is the common ostrich, up to tall and weighs between . The smallest non-avialan theropod known from adult specimens may be Anchiornis huxleyi, at in weight and in length.
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In their 2015 re-description of Sigilmassasaurus, Evers and colleagues argued that Sigilmassasaurus was in fact a distinct genus from Spinosaurus, and therefore doubted whether the material assigned to Spinosaurus by Ibrahim et. al. should be assigned to Spinosaurus or Sigilmassasaurus. In 2018, an analysis by Henderson found that Spinosaurus probably was competent at bipedal terrestrial locomotion; the center of mass was instead found to be close to the hips, allowing Spinosaurus to stand upright like other bipedal theropods.
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Godefroit et al. concluded that the filaments earlier reported in Ornithischia, with Psittacosaurus and Tianyulong, could be homologous to the "protofeathers" found in non-avian theropods. With known feather-like structures in pterosaurs, there is evidence for it being basal to Ornithodira. An attempt to reconstruct the likely ancestral state of dinosaurs found it to be likely that both Ornithodira and Dinosauria were ancestrally scaly, however, this result was only obtained when assuming that early pterosaurs were scaly.
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The rock facies of the Barun Goyot Formation are considered to be the result of an arid or semi- arid environment, with aeolian (deposited by wind) beds. Other known mammals from the Red Beds of Hermiin Tsav include the multituberculates Nemegtbaatar, Chulsanbaatar and Nessovbaatar, and the therians Deltatheridium, Asioryctes, and Barunlestes. Dinosaurs include Ajancingenia, Velociraptor, Saichania, Platyceratops, Gobiceratops, and some indeterminate theropods. Reptiles include the turtle Mongolemys, the lizards Gobinatus, Tchingisaurus, Prodenteia, Gladidenagama and Phrynosomimus, and an indeterminate crocodile.
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Life restoration of Lourinhanosaurus based on ML 370 and skeletal reconstructions L. antunesi was rather large. The individual found was a sub-adult, measuring some 4.5 m in length and weighing around 160 kg. Histology shows that the holotype specimen was between 14 and 17 years old. Though gastroliths have been found in other theropods since the description of L. antunesi, this was the first theropod dinosaur for which this kind of remains have been assigned.
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Photograph of specimen and diagram showing plumage Anchiornis is notable for its proportionally long forelimbs, which measured 80% of the total length of the hindlimbs. This is similar to the condition in early avians such as Archaeopteryx, and the authors pointed out that long forelimbs are necessary for flight. Anchiornis also had a more avian wrist than other non-avialan theropods. The authors initially speculated that it would have been possible for Anchiornis to fly or glide.
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Theropods normally have four premaxillary teeth and the previous record for this group was seven, as found in spinosaurids. In Halskaraptor, the premaxillary teeth are very closely packed, touching each other, and are very elongated, gradually curving to behind. The teeth in the maxilla, estimated in number at twenty to twenty-five, are more robust, curve only at their tips, and are spaced at a larger distance. They are more transversely flattened, with an oval cross-section.
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Eberth, D.A., and Hamblin, A.P., 1993 , Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and northern Montana: Canadian Journal of Earth Sciences, 30, 174‒200. This formation has produced the remains of the theropods Saurornitholestes, Daspletosaurus, Troodon, and Dromaeosaurus, the ceratopsids Albertaceratops, Chasmosaurus, Anchiceratops, and Coronosaurus, the hadrosaurids Brachylophosaurus, Gryposaurus, Parasaurolophus, and Corythosaurus, as well as other dinosaurs that shared that their paleoenvironment with Albertadromeus.
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By 1949, when administration of the area passed to the Chinese Communist Party and its leader Mao Zedong, the fossils of Yixian were studied only by Chinese scientists. It was not until the 1990s when remarkable fossils of birds and dinosaurs were excavated. Since 1996, a number of dinosaur fossils that have revolutionized knowledge of these animals have been found at Yixian; among them are the first known non-avian theropods with feathers. See Jehol Biota.
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Outdated quadrupedal, prosauropod-like restoration of Erlikosaurus Erlikosaurus was by Perle assigned to the Segnosauridae, a group today known as the Therizinosauridae, confirmed by later cladistic analyses. Therizinosaurs were a strange group of theropods that ate plants instead of meat, and had a backward-facing pubis, like ornithischians. Also like ornithischians, their jaws were tipped by a broad rounded bony beak useful for cropping off plants. The relationships of therizinosaurs were quite complicated when the first members were discovered.
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Researchers have presented evidence and arguments for air sacs in sauropods, "prosauropods", coelurosaurs, ceratosaurs, and the theropods Aerosteon and Coelophysis. In advanced sauropods ("neosauropods") the vertebrae of the lower back and hip regions show signs of air sacs. In early sauropods only the cervical (neck) vertebrae show these features. If the developmental sequence found in bird embryos is a guide, air sacs actually evolved before the channels in the skeleton that accommodate them in later forms.
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The most probable reason for the bony studs and plates is that it evolved for defence against theropods like Abelisaurus and Carnotaurus. Saltasaurine armour has led to controversies. In 1929 the paleontologist Friedrich von Huene named the genus Loricosaurus for armour he thought to be from ankylosaurians. These bones were found to have similarities to those later discovered on sauropods like Saltasaurus and Neuquensaurus, and as such, Loricosaurus may be the same as one of the other genera.
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In 2017 Foth and Rauhut in their re-evaluation of the Haarlem Archaeopteryx specimen (which they classified it in its own distinct genus Ostromia) found that the anchiornithids are a distinct family closer to the ancestry of birds. They provided their own definition of Anchiornithidae as "as all maniraptoran theropods that are more closely related to Anchiornis huxleyi than to Passer domesticus, Archaeopteryx lithographica, Dromaeosaurus albertensis, Troodon formosus, or Oviraptor philoceratops." During the description of Halszkaraptor, Cau et al.
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No other fossil vertebrates were found with the remains of Afromimus at the Gadoufaoua locality. However, other dinosaurs are known from Gaoufaoua: the theropods Suchomimus/Cristatusaurus, Kryptops, and Eocarcharia; the sauropod Nigersaurus; and the ornithopods Ouranosaurus, Lurdusaurus, and Elrhazosaurus. Other fauna include crocodilians, such as Sarcosuchus, Stolokrosuchus, Araripesuchus, and Anatosuchus; turtles of the genera Teneremys, Platycheloides, Taquetochelys, and Araripemys; and fish, including the coelacanth Mawsonia, the lungfish Ceratodus, and the ray-finned fish Lepidotes and Pliodetes.
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An adult Tyrannosaurus rex weighed about as much as an African elephant. If large tyrannosauroids were endotherms, they would have needed to radiate heat efficiently.Norell, M. Xu, X. (2005) "The Varieties of Tyrannosaurs" Natural History Magazine May 2005. However, due to the different structural properties of feathers compared to fur, as well as a larger surface area per cubic square meter, it is extremely unlikely even the largest theropods would suffer overheating issues from an extensive feather coat.
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Additionally, some specimens have iridescent feathers. Pigmented and iridescent feathers may have provided greater attractiveness to mates, providing enhanced reproductive success when compared to non-colored feathers. Current research shows that it is plausible that theropods would have had the visual acuity necessary to see the displays. In a study by Stevens (2006), the binocular field of view for Velociraptor has been estimated to be 55 to 60 degrees, which is about that of modern owls.
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It underwent a drastic morphological transformation as it aged: while juveniles were toothed, these teeth were completely lost and replaced by a beak with age. Several of these features were convergently similar to the later ornithomimid theropods as well as the earlier non-dinosaurian shuvosaurids. Limusaurus was the first known member of the group Ceratosauria from Asia. It belonged to the Noasauridae, a family of small and lightly built ceratosaurs, along with its closest relative Elaphrosaurus.
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A recent study conducted by Hartman et al. 2019, proposed a placement of Dakotaraptor in the "Unenlagiidae". If this study proves correct, then Dakotaraptor would have been one of the northernmost genera of Unenlagiine known. Graph comparing tooth dimensions of Dakotaraptor with those of other theropods In the recently performed phylogenetic by Currie and Evans in 2019, Dakotaraptor was again recovered as an eudromaeosaur, though the authors noted that the holotype may not represent one individual.
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Size compared to a human Xiongguanlong was a bipedal animal which balanced its body with a long tail, like most other theropods. It was intermediate in size between earlier tyrannosauroids from the Barremian and later tyrannosaurids from the Late Cretaceous, such as Tyrannosaurus, and has been estimated to weigh about . The vertebrae were more robust than in other basal tyrannosauroids, possibly to better support a big skull.Livescience: ”T. Rex Relative Fills Evolutionary Gap”, 22-4-2009.
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In places fossil sea cucumbers are abundant. During the late Albian, from about 115 to 110 million years ago sauropods and theropods left many footprints in the sediments that would later come to compose the Glen Rose Formation. The widely spaced limbs of the sauropod trackmakers suggest that they were likely brachiosaurids. Most of the tracks were left on an ancient coastal plain bordering the ancient Gulf of Mexico, although some were left in lagoonal sediments or intertidal areas.
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Siats /see-ats/ is an extinct genus of large neovenatorid theropod dinosaur known from the Late Cretaceous Cedar Mountain Formation of Utah, US. It contains a single species, Siats meekerorum. S. meekerorum could be the first neovenatorid discovered in North America and the geologically youngest allosauroid yet discovered from the continent. It was initially classified as a megaraptoran, a clade of large theropods with very controversial relationships. This group may be examples of tyrannosauroids, neovenatorid allosauroids, or basal coelurosaurs.
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Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, maniraptorans, and birds. Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed.
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Tetanurans have two basic skull morphologies. The first skull type, typical in large theropods such as Allosaurus, is common within ceratosaurs and may be primitive for tetanurans. In this type, the skull is about three times longer than tall, with a blunter snout and frequent elaborations such as horns or spikes along the lacrimals, nasals, and frontals. In the second skull type, the skull is lower and longer, with a less elaborated skull roof and a more elongated snout.
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The major defining characteristics of Ceratosauria include a robust skull with increased ornamentation or height and a shortening of the arms. Both of these characteristics are generally accentuated in later members of the group, such as the abelisaurs, whereas more basal species such as C. nasicornis appear more similar to other basal theropods. The highly fragmented nature of the ceratosaur fossil record means that the characteristics, relationships, and early history of Ceratosauria remain mysterious and highly debated.
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The fossils of Ajkaceratops were discovered in the Csehbánya Formation, which is interpreted as "a floodplain and channel deposit formed by variegated clay, silt with interbedded grey and brown sand, and sandstone beds". This strata dates to the Santonian stage, around 86 to 84 mya (million years ago). Ajkaceratops shared its environment with other dinosaurs such as Rhabdodon, nodosaurid ankylosaurs, Non-Avian theropods and enantiornithine birds, as well as eusuchian crocodiles, azhdarchid pterosaurs, bothremydid turtles and teiid lizards.
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Therefore, Carnotaurus could have been one of the fastest large theropods. While the caudofemoralis muscle was enlarged, the epaxial muscles situated above the caudal ribs would have been proportionally smaller. These muscles, called the longissimus and spinalis muscle, were responsible for tail movement and stability. To maintain tail stability in spite of reduction of these muscles, the caudal ribs bear forward projecting processes interlocking the vertebrae with each other and with the pelvis, stiffening the tail.
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The first and fourth metacarpals were short, while the second was slightly longer than the third. The metacarpus and especially the first phalanges were proportionally very short, unlike in most other basal theropods. Only the first phalanges of digits II, III, and IV are preserved in the holotype; the total number of phalanges and unguals (claw bones) is unknown. The anatomy of metacarpal I indicates that phalanges had originally been present on this digit, as well.
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In addition to the large nasal horn, Ceratosaurus possessed smaller, semicircular, bony ridges in front of each eye, similar to those of Allosaurus. These ridges were formed by the lacrimal bones. In juveniles, all three horns were smaller than in adults, and the two halves of the nasal horn core were not yet fused. The premaxillary bones, which formed the tip of the snout, contained merely three teeth on each side, less than in most other theropods.
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Carcharodontosaurus is a genus of carnivorous carcharodontosaurid dinosaurs that existed during the Cenomanian stage of the mid-Cretaceous Period in Northern Africa. It is currently known to include two species: C. saharicus and C. iguidensis, which are among the larger theropods, nearly as large as or even larger than Tyrannosaurus, Giganotosaurus, and Spinosaurus. The genus Carcharodontosaurus is named after the shark genus Carcharodon, itself composed of the Greek (, meaning "jagged" or "sharp") and (, "teeth"), and the suffix ' ("lizard").
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Dinosaurs of the Shaximiao Formation The Shaximiao Formation has produced mainly sauropods, but has also held numerous other dinosaur types, such as theropods and stegosaurians amongst others. In total, over 8,000 pieces of bone have been unearthed from the area - amounting to nearly 40 tonnes. The site was unknown until the early 1970s, when a Chinese gas company unearthed Gasosaurus in 1972. It would be the first of the many dinosaurs to be uncovered from the area.
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Sinotyrannus, one of the largest known proceratosaurids The family belongs to the tyrannosaur lineage. It was first named in 2010 by Oliver Rauhut and colleagues in their re-evaluation of the type genus, Proceratosaurus. Their study supported the idea that Proceratosaurus is a coelurosaur, a tyrannosauroid, and most closely related to the Chinese tyrannosauroid Guanlong. They defined the clade containing these two dinosaurs as all theropods closer to Proceratosaurus than to Tyrannosaurus, Allosaurus, Compsognathus, Coelurus, Ornithomimus, or Deinonychus.
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Another way of classification of Compsognathidae is shared metacarpal morphology. A 2007 study found similarities between compsognathid genera in certain metacarpal I morphologies. The conclusion of this study found that Composgnathidae had a distinct manual morphology where, like theropods, the first digit of the manus is larger than the other digits, but with a distinct metacarpal I morphology where the metacarpal is stocky and short. Compsognathidae also has a projection from the manus that is on this metacarpal.
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Their eyes were also large, and pointed forward, indicating that they had good binocular vision. The ears of troodontids were also unusual among theropods, having enlarged middle ear cavities, indicating acute hearing ability. The placement of this cavity near the eardrum may have aided in the detection of low- frequency sounds. In some troodontids, ears were also asymmetrical, with one ear placed higher on the skull than the other, a feature shared only with some owls.
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As in other ornithomimids but unusually among theropods, the three fingers were roughly the same length, and the claws were only slightly curved; Henry Fairfield Osborn, describing a skeleton of S. altus in 1917, compared the arm to that of a sloth. These might have been adaptations to support wing feathers. Struthiomimus differed from close relatives only in subtle aspects of anatomy. The edge of the upper beak was concave in Struthiomimus, unlike Ornithomimus, which had straight beak edges.
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Skull cast, Dinosaur Discovery Museum, Kenosha, Wisconsin The skull, measuring in length, was proportionally shorter and deeper than in any other large carnivorous dinosaur. The snout was moderately broad, not as tapering as seen in more basal theropods like Ceratosaurus, and the jaws were curved upwards. As in other abelisaurids, the facial bones, especially the nasal bones, were sculptured with numerous small holes and spikes. In life, a wrinkled and possibly keratinous skin would have covered these bones.
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Known elements in white and unknown in dark grey. This reconstruction reflects the possible sauropodomorph affinities. Adding Nhandumirim to the second analysis, created by Nesbitt & Ezcurra (2015), led to inconclusive results. In the strict consensus tree (average result of most parsimonious trees), Nhandumirim is part of a broad polytomy at the base of Saurischia, along with several traditional basal theropods, herrerasaurids, and Eoraptor (which, on the other hand, is frenquently considered an early sauropodomorph in most recent analyses).
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"The allosaur-tyrannosaur group", Predatory Dinosaurs of the World. 301–347. but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria. Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review. Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus.
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Inside the lacrimal bones were depressions that may have held glands, such as salt glands. Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus; they may have been related to the sense of smell, perhaps holding something like Jacobson's organs. The roof of the braincase was thin, perhaps to improve thermoregulation for the brain. The skull and lower jaws had joints that permitted motion within these units.
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In the seventies, Samuel Paul Welles and Jaime Emilio Powell prepared a study on European theropods, planning to name a separate genus "Walkersaurus". Their manuscript remained unpublished but in 1994 and 1995 Stephan Pickering divulged parts of it, also containing the name "Walkersaurus hesperis".Pickering, S., 1995. "Jurassic Park: Unauthorized Jewish Fractals in Philopatry" in: A Fractal Scaling in Dinosaurology Project, 2nd revised printing, Capitola, California This is generally considered an invalid nomen nudum or nomen non rite publicatum.
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Another autapomorphy of Tratayenia is that the prezygodiapophyseal lamina is parallel to the paradiapophyseal lamina. Other theropods either have a weakly developed (or absent) paradiapophyseal lamina, or one which is angled relative to the prezygodiapophyseal lamina. The front edge of each vertebra has a third autapomorphy, related to two pairs of laminae (four total) connecting the prezygapophyses to the neural spines. At the base of the neural spines, the two laminae comprising each pair are very close together.
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Megaraptorans have very controversial relations to other theropods. The first mainstream hypothesis is that they are carnosaurs, distantly related to Allosaurus and more closely related to Neovenator and carcharodontosaurids. The second popular hypothesis considers them to be basal tyrannosauroids, part of the coelurosaur lineage which includes the crested proceratosaurids as well as the famous tyrannosaurids such as Tyrannosaurus. A third hypothesis also considers them to be coelurosaurs, but outside Tyrannosauroidea and basal to practically all other groups of Coelurosauria.
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Several notable taxa are cursorial, including some mammals (such as wolverines and wolves, ungulates, agoutis, and kangaroos) and birds (such as the ostrich), as well as some dinosaurs (such as theropods, and Heterodontosauridae). Several extinct archosaurs were also cursorial, including the crocodylomorphs Pristichampsus, Hesperosuchus, and several genera within Notosuchia. Jumping spiders and other non-web based spiders generally walk throughout the day, so that they maximize their chances of a catch, and web-based spiders run away if threatened.
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Behaviours influenced by high EQs include nest-building, parental care, and bird-like sleeping, some of which have been shown to be present in Psittacosaurus. Restoration of P. mongoliensis The senses of Psittacosaurus can be inferred from the endocast. Large olfactory bulbs are present, indicating the genus had an acute sense of smell. The size of these bulbs are comparable to large predatory theropods, although they likely evolved to avoid predators instead of to seek out prey.
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Reisdorf and Wuttke (2012) described the taphonomical phenomena of the German specimen of Compsognathus. The number of digits on the hand of Compsognathus has been a source of debate. For much of its history, Compsognathus was typically depicted with three digits, as is typical for theropods. However, the type specimen only preserved phalanges from the first two digits, leading to the suggestion that Compsognathus bore only two functional digits, with the third metacarpal being extremely slender and reduced.
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The majority of dinosaurs known to have had feathers or protofeathers are theropods, however featherlike "filamentous integumentary structures" are also known from the ornithischian dinosaurs Tianyulong and Psittacosaurus. The exact nature of these structures is still under study. However, it is believed that the stage-1 feathers (see Evolutionary stages section below) such as those seen in these two ornithischians likely functioned in display. In 2014, the ornithischian Kulindadromeus was reported as having structures resembling stage-3 feathers.
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Majungasaurus crenatissimus, top land predator of the formation Animals found in the formation include frogs (including Beelzebufo ampinga), turtles, snakes, lizards, at least seven species of crocodyliforms (including species of Mahajangasuchus and Trematochampsa), abelisaurid theropods Majungasaurus, noasaurid Masiakasaurus, two types of titanosaurian sauropods (Rapetosaurus and Vahiny), and at least five species of birds or very bird-like dinosaurs, including Rahonavis. The long Majungasaurus was likely the apex predator in the terrestrial environment. Crocodyliforms were very diverse and abundant.
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The general homogeneity of dinosaurian faunas continued into the Middle and Late Jurassic, where most localities had predators consisting of ceratosaurians, spinosauroids, and carnosaurians, and herbivores consisting of stegosaurian ornithischians and large sauropods. Examples of this include the Morrison Formation of North America and Tendaguru Beds of Tanzania. Dinosaurs in China show some differences, with specialized sinraptorid theropods and unusual, long-necked sauropods like Mamenchisaurus. Ankylosaurians and ornithopods were also becoming more common, but prosauropods had become extinct.
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The smallest dinosaur known is the bee hummingbird, with a length of only and mass of around . The smallest known non-avialan dinosaurs were about the size of pigeons and were those theropods most closely related to birds. For example, Anchiornis huxleyi is currently the smallest non-avialan dinosaur described from an adult specimen, with an estimated weight of and a total skeletal length of . The smallest herbivorous non-avialan dinosaurs included Microceratus and Wannanosaurus, at about long each.
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Congregating into herds may have evolved for defense, for migratory purposes, or to provide protection for young. There is evidence that many types of slow-growing dinosaurs, including various theropods, sauropods, ankylosaurians, ornithopods, and ceratopsians, formed aggregations of immature individuals. One example is a site in Inner Mongolia that has yielded the remains of over 20 Sinornithomimus, from one to seven years old. This assemblage is interpreted as a social group that was trapped in mud.
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However, some scientists have claimed the only consequence would be to push the point of bird divergence further back in time. At the time when such claims were originally made, the affiliation of birds and maniraptoran theropods which today is well-supported and generally accepted by most ornithologists was much more contentious; most Mesozoic birds have only been discovered since then. Chatterjee himself has since used Protoavis to support a close relationship between dinosaurs and birds.Chatterjee, S. (1997).
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A region of the holotype where the enamel (outer layer of the teeth) has weathered away reveals that these flutes extend down to the dentin (second layer of the teeth). The enamel also has a granular (finely wrinkled) texture, as seen in teeth from the spinosaurid Baryonyx. Some of the root is preserved in the holotype and, as in all theropods, there is a large pocket for the tooth pulp, which would have housed blood vessels and nerves.
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Yates, A.M., 2006 (for 2005). "A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods." Palaeontologia Africana, 41: 105-122. But later studies found Zupaysaurus to be a sister taxon sister to a clade containing dilophosaurids, ceratosaurs and tetanurans.Smith N.D., Makovicky P. J., Hammer W. R. & Currie P. J. 2007 Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution. Zool.
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The of the cervical vertebrae were not always sutured to the (the bodies of the vertebrae), and the there were low and thin. The were short, similar to those of crocodiles, and possibly overlapped each other somewhat. The centra of the dorsal vertebrae of the back were similar in size. Like in other theropods, the skeleton of Baryonyx showed skeletal pneumaticity, reducing its weight through (openings) in the neural arches and (hollow depressions) in the centra (primarily near the ).
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Life restoration The neck is relatively narrow in comparison to abelisaurids and bear stout neck ribs. While many theropods have s-shaped necks, the ribs would make the neck rather stiff in Masiakasaurus, and the back of the neck is positioned almost horizontally, giving it only a slighter curve. Like those of other abelisauroids, the vertebrae are heavily pneumaticized, or hollowed, and have relatively short neural spines. Pneumaticity is limited to the neck and foremost back vertebrae, however.
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Skull diagram The procument front teeth of Masiakasaurus were likely an adaptation for grasping small prey. They would have been unsuitable for tearing larger food apart. In the front of the jaws, carinae are restricted to the base of the teeth and would not have been used to tear prey. The back teeth, however, share the same general characteristics as those of most other theropods, suggesting that they served a similar function in Masiakasaurus such as cutting and slicing.
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The phylogeny and taxonomy of Coelurosauria has been subject to intensive research and revision. For many years, Coelurosauria was a 'dumping ground' for all small theropods. In the 1960s several distinctive lineages of coelurosaurs were recognized, and a number of new infraorders were erected, including the Ornithomimosauria, Deinonychosauria, and Oviraptorosauria. During the 1980s and 1990s, paleontologists began to give Coelurosauria a formal definition, usually as all animals closer to birds than to Allosaurus, or equivalent specifiers.
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Ardley Trackways is a geological Site of Special Scientific Interest north- west of Bicester in Oxfordshire. It is a Geological Conservation Review site. This site is internationally important because it has trackways created by a herd of sauropod (herbivorous) dinosaurs, together with several carnivorous theropods, along a shoreline dating to the Middle Jurassic, around 165 million years ago. These are the only such trackways in England, and one of the few dating to the Middle Jurassic in the world.
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Restoration of two individuals playing in snow Stenonychosaurus are thought to have been predators, a view supported by its sickle claw on the foot and apparently good binocular vision. Stenonychosaurus teeth, however, are different from most other theropods. One comparative study of the feeding apparatus suggests that Stenonychosaurus could have been an omnivore.Holtz, Thomas R., Brinkman, Daniel L., Chandler, Chistine L. (1998) Denticle Morphometrics and a Possibly Omnivorous Feeding Habit for the Theropod Dinosaur Troodon. Gaia number 15.
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The three semicircular canals of the inner ear of Carcharodontosaurus saharicus, when viewed from the side, had a subtriangular outline. This subtriangular inner ear configuration is present in Allosaurus, lizards, turtles, but not in birds. The semi-"circular" canals themselves were actually very linear, which explains the pointed silhouette. In life, the floccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in other non-avian theropods, birds, and pterosaurs.
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However, the apparent increase in dinosaur footprint size has instead been argued to be a result of increasing abundance of large theropods, rather than an abrupt acquisition of large size. Some "rauisuchians" may have existed in the very early Jurassic based on bone fragments from South Africa, but this identification is tentative. The name "Rauisuchia" comes from the genus Rauisuchus, which was named after fossil collector Dr. Wilhelm Rau. The name Rauisuchus means Wilhelm Rau's crocodile.
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Other features of Smok seem to exclude it from these groups of archosaurs. The premaxilla and maxilla of the upper jaw attach closely to each other, making a continuous row of evenly spaced teeth. Early theropods and orthithosuchids have a toothless gap between the premaxilla and the maxilla, distinguishing them from Smok. The upper jaw bones of rauisuchians are not closely connected, leaving a small opening between the premaxilla and maxilla that is not seen in Smok.
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Apsaravis also retains primitive characters shared with Enantiornithes and more basal theropods, including a narrow intercondylar groove and barrel-shaped condyles of the tibiotarsus, a dorsal fossa of the coracoid, into which the supracoracoideus nerve foramen opens, and several features of the humerus. This intermediate anatomy is evidence against the validity of the clade "Sauriurae".Clarke, Julia A., Norell, Mark A. (2002). "The morphology and phylogenetic position of Apsaravis ukhaana from the Late Cretaceous of Mongolia".
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Also from the section of the formation are the theropods Daspletosaurus, and Saurornitholestes, the hadrosaurids Brachylophosaurus, Gryposaurus and Parasaurolophus, the ankylosaurid Scolosaurus, and the ceratopsians Coronosaurus and Chasmosaurus. Other genera are known, but do not persist from the upper section of the formation, and therefore are not contemporaries of Corythosaurus. Corythosaurus casuarius is widespread throughout the lower unit of the Dinosaur Park Formation. In it, Corythosaurus was found to be closely associated with the ceratopsid Centrosaurus apertus.
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In a 2006 conference abstract, Sara Burch presented the inferred range of motion in the arms of the therizinosaur Neimongosaurus and concluded the overall motion at the -humeral joint at the shoulder was roughly circular, and directed sideways and slightly downwards, which diverged from the more oval, backwards-and- downwards-directed ranges of other theropods. This ability to extend their arms considerably forwards may have helped therizinosars reach and grasp for foliage. In 2009, Zanno and colleagues stated therizinosaurs were the most- widely regarded candidates for herbivory among theropods and listed features associated with this diet. These included small, densely packed, coarse serrations; lanceolate (lance-shaped) teeth with a low replacement rate; a beak at the front of the jaws; an inset tooth row that suggests fleshy cheeks; an elongated neck; a small skull; a very large gut capacity as indicated by the rib circumference at the trunk and the outwards flaring processes of the ilia; and the loss of cursorial (related to running) adaptations in the hind limbs, including development of functionally tetradactyl feet.
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The scapula had a rectangular acromion, or attachment site for clavicle (collarbone). The (upper arm bone) was very strongly built, only equaled in size among non-spinosaurid theropods by that of Megalosaurus and Torvosaurus, with robust upper corners. The humerus had a boss (bone overgrowth) above the condyle that contacted its hook-shaped (forearm bone). Accordingly, the of the lower arm was well-developed with an enormous olecranon (upper process set-off from the shaft), an exceptional trait shared with Baryonyx.
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American palaeontologist Thomas Holtz noted that spinosaurid teeth were adapted for grasping rather than slicing, hence their reduced serrations, which in most other theropods were more prominent. Suchomimus's extensive secondary palate, which would have made the roof of the mouth more solid, allowed it to better resist twisting forces exerted by prey. The rest of Suchomimus's body was not particularly adapted to the water. The discovery of Suchomimus revealed that spinosaurid skulls were significantly shallower, more elongated and narrow than previously thought.
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Originally thought to be one of the earliest members of flightless birds, alvarezsaurids have recently been regarded as more basal theropods. Skeletal remains suggest that they had tiny but stout forelimbs and compact birdlike hands. The skeletal structure also suggests that this dinosaur possessed significant breast and arm muscles that were likely adapted for tearing and digging. They had elongate jaws with minute teeth and a tubular snout that suggests they could have been adapted to feed on insects such as termites.
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The close of the Cretaceous period saw the demise of the Mesozoic era reptilian megafauna. Along with massive amount of volcanic activity at the time, the meteor impact that created the Cretaceous–Paleogene boundary is accepted as the main cause for this mass extinction event. Of the large marine reptiles, only sea turtles are left, and, of the dinosaurs, only the small feathered theropods survived in the form of birds. The end of the “Age of Reptiles” led to the “Age of Mammals”.
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Dinosaurs known from the Morrison include the theropods Ceratosaurus, Ornitholestes, and Torvosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Other vertebrates that shared this paleoenvironment included ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, and several species of pterosaurs. Shells of bivalves and aquatic snails are also common. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers.
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Wulatelong shared their habitat in the Bayan Mandahu with a number of other dinosaurian fauna. These included the ceratopsians Protoceratops and Magnirostris, the ankylosaurian Pinacosaurus, and a number of other theropods: the dromaeosaurids Velociraptor and Linheraptor, the oviraptorosaurian Machairasaurus, the alvarezsauroid Linhenykus, and the troodontid Linhevenator. The authors of the paper describing Wulatelong concluded that the Bayan Mandahu fauna "differs fundamentally in composition from the classical Djadokhta fauna, perhaps because of a difference in age" or due to environmental factors.
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In contrast to most therizinosaurids, Erlikosaurus was a small member reaching nearly in length and in mass. It had a well-developed beak at the snout tip and toothed jaws that were used for its herbivorous diet. The feet ended in four toes with the first one articulated to the ankle—in contrast to the vestigial first toe of most theropods. Like other therizinosaurids, Erlikosaurus had a large gut for food processing, strong arms ending in elongated claws, and a backwards directed pelvis.
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The display has a unique representation through a cladogram which defines the features of the major groups of the period. Information on display relates to the anatomical features such as weight, neck bonding, arm musculature, circulatory system and the relative size of the skull. ;Theropods and others The theropod’s aggressive aspects are shown in the form of their teeth and claws. Ornithopods, which are vegetarian by habit are shown with snouts, tooth batteries, mobile skull bones jowls and with hoped feet.
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Tyrannosauroid hindlimbs are longer relative to body size than almost any other theropods, and show proportions characteristic of fast-running animals, including elongated tibiae and metatarsals. These proportions persist even in the largest adult Tyrannosaurus, despite its probable inability to run. The third metatarsal of tyrannosaurids was pinched at the top between the second and fourth, forming a structure known as the arctometatarsus. The arctometatarsus was also present in Appalachiosaurus but it is unclear whether it was found in Eotyrannus or Dryptosaurus.
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Visual acuity for Tyrannosaurus has been predicted to be anywhere from about that of humans to 13 times that of humans. However, as both Velociraptor and Tyrannosaurus have a rather extended evolutionary relationship with the more basal theropods, it is unclear how much of this visual acuity data can be extrapolated. The idea that precursors of feathers appeared before they were co-opted for insulation is already stated in Gould and Vrba, 1982. The original benefit might have been metabolic.
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Limusaurus had three fingers (the middle three), as compared to the five fingers of more basal relatives; it was unique in that the first finger was missing entirely, and the first metacarpal was shorter than the other metacarpals. The second metacarpal was more robust than the other metacarpals, which is another distinctive feature of the genus. The second finger had three phalanges (finger bones). The third finger also only had three phalanges, as opposed to four in other early theropods.
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Sigilmassasaurus, from Morocco, and "Spinosaurus B", from Egypt, represent a fourth type of large predator. This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over one tonne in weight, as well as several smaller genera. Differences in head shape and body size among the large North African theropods may have been enough to allow niche partitioning as seen among the many different predator species found today in the African savanna.
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Iguanacolossus compared to the fauna of the Yellow Cat Member from the Cedar Mountain Formation (Iguanacolossus in green) Iguanacolossus was recovered in the Yellow Cat Member from the Cedar Mountain Formation. However, this Member is divided in two beds: Upper and Lower Yellow Cat; Iguanacolossus was unearthed from the Lower bed, where it shared its environment with Theropods: Falcarius, Geminiraptor and Yurgovuchia. The sauropod Mierasaurus and the turtle Naomichelys. There are also indeterminate Goniopholidids crocodiles known from the Lower Yellow Cat.
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They have been found with Hypsilophodon, Othnielosaurus, Parksosaurus, Talenkauen, Thescelosaurus, and Macrogryphosaurus to date. Size of a variety of numerous ornithopods The early ornithopods were only about 1 metre (3 feet) long, but probably very fast. They had a stiff tail, like the theropods, to help them balance as they ran on their hind legs. Later ornithopods became more adapted to grazing on all fours; their spines curved, and came to resemble the spines of modern ground-feeders such as the bison.
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They set the bird group as representing the theropods with the reptiles representing the sauropod group. The laid eggs of each species where compared with one another over the course of the study as well as against the fossilized eggs. The results that was retrieved from the experiment was that while sauropods laid smaller eggs in greater amounts each year, dinosaur of the theropod group was revealed to lay larger eggs less frequently over the years, similar to modern birds today.
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Chambers, Paul, (2002), Bones of Contention, John Murray (Publishers) Ltd, London, p. 249 Furthermore, the authenticity of "Archaeoraptor" would not have been an essential proof for the hypothesis that birds are theropods, as this is sufficiently corroborated by other data; paleontologist Christopher Brochu concluded in November 2001: "That birds are derived theropod dinosaurs is no longer the subject of scholarly dispute."Brochu, Christopher A. (2001), "Progress and future directions in archosaur phylogenetics", Journal of Paleontology: Vol. 75, No. 6, pp.
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These ridges, known as centrodiapophyseal laminae, defined a large depression (infradiapophyseal fossa) under the transverse processes. Although these ridges were also present in dorsal (back) vertebrae and have been found in other theropods, megaraptorans were practically unique in the fact that their centrodiapophyseal laminae were well-developed at the base of the tail, sometimes even more so than the dorsal vertebrae. Only spinosaurids share this feature. The strong development of these ridges may indicate that the tail was deep and muscular.
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The tendency for fusion between the coracoid and scapula stems from their developmental origins as a unified homogenous condensation. However, that coalescence becomes detached during chondrogenesis because the osteogenic pattern and/or the differentiation of the preskeletogenic cells is delayed, resulting a sutural contact between the elements. The fusion between the coracoid and scapula is present predominantly in non-avian theropods. However, these two elements are separated in Archaeopteryx, and in more crownward avian clades, but fused in stemward pygostylians confuciusornithids and jinguornithids.
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This indicates a growth rate that is faster than in most large non-avian theropods. The existence of giant oviraptorosaurians, such as Gigantoraptor, explains several earlier Asian finds of very large, up to 53 centimetres long, oviraptorosaurian eggs, assigned to the oospecies Macroelongatoolithus carlylensis. These were laid in enormous rings with a diameter of three metres. The presence of Macroelongatoolithus in North America indicates that gigantic oviraptorosaurs were present there as well, though no fossil skeletal remains have been found.
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Troodontids are a group of small, bird-like, gracile maniraptorans. All troodontids have unique features of the skull, such as large numbers of closely spaced teeth in the lower jaw. Troodontids have sickle-claws and raptorial hands, and some of the highest non-avian encephalization quotients, suggesting that they were behaviourally advanced and had keen senses. They had unusually long legs compared to other theropods, with a large, curved claw on their retractable second toes, similar to the "sickle-claw" of the dromaeosaurids.
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Reconstructed skull of Marshosaurus at the Carnegie Museum of Natural History, based on referred material During the 1960s, over fourteen thousand fossil bones were uncovered at the Cleveland-Lloyd Quarry in central Utah. The majority of these belonged to Allosaurus but some were of at least two theropods new to science. In 1974 one of these was named by James Henry Madsen Jr. as the genus Stokesosaurus. In 1976 the second was by Madsen named as the type species Marshosaurus bicentesimus.
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Struthiomimus is a member of the family Ornithomimidae, a group which also includes Anserimimus, Archaeornithomimus, Dromiceiomimus, Gallimimus, Ornithomimus, and Sinornithomimus. Just as the fossil remains of Struthiomimus were incorrectly assigned to Ornithomimus, the larger group that Struthiomimus belongs to, the Ornithomimosauria, also underwent many changes over the years. For example, O.C. Marsh initially included Struthiomimus in the Ornithopoda, a large clade of dinosaurs not closely related to theropods. Five years later, Marsh classified Struthiomimus in the Ceratosauria.O. C. Marsh. 1896.
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Dinosaurs dominate the fauna, especially hadrosaurs, which make up half of all dinosaurs known, including the genera Edmontosaurus, Saurolophus and Hypacrosaurus. Ceratopsians and ornithomimids were also very common, together making up another third of the known fauna. Along with much rarer ankylosaurians and pachycephalosaurs, all of these animals would have been prey for a diverse array of carnivorous theropods, including troodontids, dromaeosaurids, and caenagnathids. Intermingled with the Albertosaurus remains of the Dry Island bonebed, the bones of the small theropod Albertonykus were found.
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560 pp. . The legs were not as long or suited for speed as those of tyrannosaurids, and the claws of the toes were less developed and more hoof-like than those of earlier theropods. Each foot had three weight-bearing toes and an inner dewclaw, which Madsen suggested could have been used for grasping in juveniles. There was also what is interpreted as the splint-like remnant of a fifth (outermost) metatarsal, perhaps used as a lever between the Achilles tendon and foot.
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Furthermore, the small number of injured Majungasaurus specimens observed amongst those recovered indicates most well preserved individuals generally lack observable pathologies, while a few select individuals were shown to have possessed multiple pathologies, a general pattern also noted in other large, nonavian theropods. Such patterns may be the result of a snowball effect where one injury or an infection increased the likelihood of additional maladies and injuries due to functional impairment or compromised immune systems in individuals once an initial injury had occurred.
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The rest of the body was also more similar to that of conventional theropods, with a neck, arms, and legs of moderate length. At least one noasaurine, the eponymous Noasaurus, had a large and deeply curved "sickle-shaped" claw of the hand. The diet of noasaurines is difficult to determine, with hypotheses ranging from fish to insects or other small animals. Rauhut & Carrano (2016) found only a single unambiguous trait used to diagnose noasaurines to the exception of other noasaurids.
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They included small hunters like Coelophysis and (possibly) larger predators like Dilophosaurus. These successful animals continued from the Late Carnian (early Late Triassic) through to the Toarcian (late Early Jurassic). Although in the early cladistic classifications they were included under the Ceratosauria and considered a side-branch of more advanced theropods,Rowe, T., and Gauthier, J., (1990). "Ceratosauria." Pp. 151–168 in Weishampel, D. B., Dodson, P., and Osmólska, H. (eds.), The Dinosauria, University of California Press, Berkeley, Los Angeles, Oxford.
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Allosaurus was one of the first dinosaurs classified as a theropod. In 1956, "Theropoda" came back into use—as a taxon containing the carnivorous dinosaurs and their descendants—when Alfred Romer re-classified the Order Saurischia into two suborders, Theropoda and Sauropoda. This basic division has survived into modern paleontology, with the exception of, again, the Prosauropoda, which Romer included as an infraorder of theropods. Romer also maintained a division between Coelurosauria and Carnosauria (which he also ranked as infraorders).
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W. H. Freeman & Company, New York. The ascending process of the astragalus is reduced, a character entirely incongruous with a highly derived status for Protoavis. Curiously, such abbreviation of the ascending process is found in ceratosaurs, and in its general osteology, the Protoavis tarsus and pes, is quite similar to those of non-tetanuran theropods. Chatterjee's restoration of the hallux as reversed is nothing more than speculation, as the original spatial relationships of the pedal elements are impossible to ascertain at this time.
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The largest sauropods increased their size by five orders of magnitude after hatching, more than in any other amniote animals. Hallett and Wedel argued size increases in the evolution of sauropods were commonly followed by size increases of their predators, theropod dinosaurs. Argentinosaurus might have been preyed on by Mapusaurus, which is among the largest theropods known. Mapusaurus is known from at least seven individuals found together, raising the possibility that this theropod hunted in packs to bring down large prey including Argentinosaurus.
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They found that the most birdlike features of oviraptorids actually place the whole clade within Aves itself, meaning that Caudipteryx is both an oviraptorid and a bird. In their analysis, birds evolved from more primitive theropods, and one lineage of birds became flightless, re-evolved some primitive features, and gave rise to the oviraptorids. This analysis was persuasive enough to be included in paleontological textbooks like Benton's Vertebrate Paleontology (2005).Osmólska, Halszka, Currie, Philip J., Barsbold, Rinchen (2004) The Dinosauria Weishampel, Dodson, Osmolska.
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Such dinosaurs as the theropods Ceratosaurus, Allosaurus, Ornitholestes, and Torvosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Hesperosaurus, Drinker, Fruitadens, Dryosaurus, and Stegosaurus are known from the Morrison. Coelurus is regarded as a small terrestrial carnivore, feeding on small prey items like insects, mammals, and lizards. It is thought to have been a fast animal, certainly faster than the similar but shorter-footed Ornitholestes. Coelurus is present in stratigraphic zones 2 and 5 of the Morrison Formation.
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Mesozoic Meanderings 2, 196 pp The species names Altispinax altispinaxRauhut, O.W.M., 2000, The interrelationships and evolution of basal theropods (Dinosauria, Saurischia). Ph.D. dissertation, University of Bristol, 440 ppRauhut, O.W.M., 2003, The Interrelationships and Evolution of Basal Theropod Dinosaurs. Special Papers in Palaeontology no. 69, London, The Palaeontological Association 213 pp and Altispinax lydekkerhueneorumPickering, S., 1995, Jurassic Park: Unauthorized Jewish Fractals in Philopatry, A Fractal Scaling in Dinosaurology Project, 2nd revised printing, Capitola, California, 478 pp are its junior objective synonyms.
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The Thermopolis specimen of Archaeopteryx, which showed that it also had a hyperextendible second toeNational Geographic News- Earliest Bird Had Feet Like Dinosaur, Fossil Shows – Nicholas Bakalar, December 1, 2005, Page 2. Retrieved 2006-10-18. In 2005, Mayr and Peters described the anatomy of a very well preserved specimen of Archaeopteryx, and determined that its anatomy was more like non-avian theropods than previously understood. Specifically, they found that Archaeopteryx had a primitive palatine, unreversed hallux, and hyper-extendable second toe.
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Size compared to a human Segnosaurus was a large-bodied therizinosaur that is estimated to have been about long and to have weighed about . Segnosaurus is incompletely known, but as a therizinosaurid, it would have been bipedal and robustly built with the trunk of the body tilted upwards compared to other theropods. The head would have been small with a (horny beak) at the tip of the jaws, and a long, slender neck. The fingers were not particularly long, but bore large claws.
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Hind part of the lower jaw Murusraptor is a megaraptoran, one of a group of large predatory dinosaurs whose exact classification remains disputed. Once believed to be dromaeosaurids, they have since been classified as either allosauroid carnosaurs or as tyrannosauroid coelurosaurs. While the discovery of Murusraptor does not clarify as of yet the placement of this group of theropods, the specimen does add further clarity to some aspects of megaraptoran anatomy and potentially, eventual classification of the Megaraptora within the theropod evolutionary tree.
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They concluded that the former was part of the Segnosauria and found this group to be a rare and aberrant group of saurischians in a position subject to change among sauropodomorphs and theropods. Dong also agreed with these similarities and placed the genus within the Segnosauridae in 1992. Nevertheless, the description of Alxasaurus in 1993 proved that the long-aberrant segnosaurs were tetanuran theropod dinosaurs and Segnosauridae was a junior synonym of the older name Therizinosauridae. Segnosauria also became synonymous with Therizinosauria.
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Close up of the shoulder spikes of AMNH 5665 The large spikes were probably used between males in contests of strength to defend territory or gain mates. The spikes would also have been useful for intimidating predators or rival males, passive protection, or for active self- defense. The large forward pointing shoulder spikes could have been used to run through attacking theropods. Carpenter suggested that the larger spikes of AMNH 5665 indicated this was a male specimen, a case of sexual dimorphism.
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Other theropods Dineobellator co-existed with were the caenagnathid Ojoraptorsaurus, ornithomimids, and troodontids, as well as Richardoestesia of uncertain affinity. Meanwhile, there are at least eight remains of mammals from the formation, such as Alphadon, Essonodon, Mesodma, and Meniscoessus, while there are five (possibly seven) types of turtle remains (Aspideretoides, Compsemys, Hoplochelys, Neurankylus, Plastomenus, and possibly Adocus and Basilemys), and four remains of fish (including Myledaphus, Squatirhina, and possibly Lepisosteus) all of which could be inferred to be common prey items for Dineobellator.
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Pangea before the split into Gondwana and Laurasia Species included in Megalosauridae have been found on every modern continent, split relatively equally between sites on the Gondwana and Laurasia supercontinents. Paleogeography findings show that Megalosauridae was mainly restricted to the Middle to Late Jurassic, suggesting they went extinct at the Jurassic-Cretaceous boundary 145 million years ago. The global radiation of these carnivorous theropods occurred in two steps. First, radiation occurred during Pangaea's breakup during the Early Jurassic, about 200 million years ago.
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Though initially beginning his research career in palaeontology with the intention of working on fossil marine reptiles, Naish became known for his doctoral work on the basal tyrannosauroid theropod Eotyrannus, a dinosaur that he, together with Steve Hutt and colleagues, named in 2001. He has published articles on the Wealden Supergroup theropods Thecocoelurus, Calamospondylus and Aristosuchus. With Martill and Dino Frey, he named a new illegally acquired Brazilian compsognathid theropod Mirischia. In 2004, Naish and Gareth Dyke reinterpreted the controversial Romanian fossil Heptasteornis.
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Some large theropods share with Smok the deep depressions of the basisphenoids in the braincase. Similarities with rauisuchians include a triangular antorbital fenestra and a connection between the ectopterygoid and jugal bones of the skull that is split into two projections. The hip of Smok has a ridge on the lateral surface of the ilium above the acetabulum. This ridge is a defining characteristic of rauisuchians, forming a buttress over the femur and giving these animals a pillar-erect stance.
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Coeluroides ("hollow form") is a small, little-known theropod dinosaur that lived during the Late Cretaceous Period in what is now India. It is known from scattered tail vertebrae discovered in the Lameta Formation. It is estimated at two meters long and perhaps thirty kilograms in weight, similar to but larger than Jubbulpuria. Coeluroides was long considered a nomen dubium because of sparse remains, but a 2004 overview of Indian theropods from the Lameta Formation found it to be probably valid.
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Most of them were based on fragmentary material, some belonging to other genera, and far less complete than that of Dromaeosaurus albertensis, and those that haven't been reclassified are considered nomina dubia today. Nevertheless, it has grown apparent that Dromaeosaurus albertensis is even rarer in its habitat than other small theropods, although it was the first dromaeosaurid of which reasonably good cranial material was described. The genus Chirostenotes was once considered to be synonymous with Dromaeosaurus at one point in time.
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Skull reconstruction There were three teeth in the premaxilla, in contrast to Herrerasaurus (which possessed four). The contact between the premaxilla and maxilla encompassed two fenestrae (holes): a subnarial fenestra which was situated low on the snout and an additional smaller fenestra positioned above it. While a subnarial fenestra is common in herrerasaurids and theropods, the additional fenestra is unique to Gnathovorax. Like other archosaurs, a small basin known as the antorbital fossa is present in front of the antorbital fenestra.
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Tyrannosaurus was one of only two theropods found to have suffered avulsion injuries, with the second being Allosaurus. Sue the T. rex, also known as FMNH PR2081, suffered an avulsion that left a divot and hook- shaped bone spur on "her" right humerus. The divot appears to be located at the origin of the deltoid or teres major muscles. Some experts have hypothesized that gout caused the formation of small patches of eroded bone discovered on Sue's first and second metacarpals.
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The authors concluded that these fractures occurred during interaction with prey. They suggested that such injuries could occur as a result of the theropod trying to hold struggling prey with its feet. Unlike injuries in the feet, which could be caused by running or migration, injuries to the hand are most likely be due to prey items resisting attack. The presence of stress fractures or tendon avulsions provide evidence for very active predatory rather than scavenging diets in the theropods.
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Artist's restoration of some megafaunal dinosaurs of the Dinosaur Park Formation. The Dinosaur Park Formation is time-equivalent to the Oldman Formation, and both formations are part of the Belly River Group. It represents the deposits of a perennial, sinuous river system and paralic environments. It is widely known for its incredible diversity of dinosaurian fauna, representing over 50 valid taxa including theropods such as dromaeosaurs, caenagnathids, troodontids, ornithomimids, and tyrannosaurids, as well as ornithischians such as pachycephalosaurs, hadrosaurs, ceratopsians, ankylosaurs, and thescelosaurs.
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Comparisons of bird and dinosaur skeletons, as well as cladistic analysis, strengthens the case for the link, particularly for a branch of theropods called maniraptors. Skeletal similarities include the neck, pubis, wrist (semi-lunate carpal), arm and pectoral girdle, shoulder blade, clavicle, and breast bone. A study comparing embryonic, juvenile and adult archosaur skulls concluded that bird skulls are derived from those of theropod dinosaurs by progenesis, a type of paedomorphic heterochrony, which resulted in retention of juvenile characteristics of their ancestors.
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Restoration Bicentenaria (meaning "two hundred year anniversary"; named after the 200th anniversary of the 1810 May Revolution in Argentina) is a genus of carnivorous coelurosaurian theropods which lived during the early Late Cretaceous (about 90 million years ago) in what is now Argentina. It contains the type species, Bicentenaria argentina. Estimates suggest that it was in length. This name was first reported in news articles in June 2012,"New species of dinosaur related to giant Tyrannosaurus." itv news, 26 June 2012.
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Prehistoric animals from the various formations of the Glen Canyon Group include several types of dinosaurs, known from both skeletal remains and tracks. Dinosaur finds in the Wingate and Moenave formations are presently almost entirely tracks. The Kayenta Formation has a diverse skeletal fauna including the theropods "Syntarsus" kayentakatae and Dilophosaurus, the prosauropod Sarahsaurus, an unnamed heterodontosaurid, and the armored dinosaurs Scelidosaurus and Scutellosaurus. The Navajo Sandstone has body fossils of the theropod Segisaurus and an Ammosaurus-like prosauropod, and tracks.
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The neck was strong and the pectoral girdle proportionally small. Part of the family Carcharodontosauridae, Giganotosaurus is one of the most completely known members of the group, which includes other very large theropods, such as the closely related Mapusaurus and Carcharodontosaurus. Giganotosaurus is thought to have been homeothermic (a type of "warm-bloodedness"), with a metabolism between that of a mammal and a reptile, which would have enabled fast growth. It may have been relatively fast moving, with a calculated maximal running speed of .
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The quadrate bone at the back of the skull was long, and had two pneumatic (air-filled) foramina (holes) on the inner side. Partial teeth, EBPM The skull roof (formed by the frontal and parietal bones) was broad and formed a "shelf", which overhung the short supratemporal fenestrae at the top rear of the skull. The jaw articulated far behind the occipital condyle (where the neck is attached to the skull) compared to other theropods. The condyle was broad and low, and had pneumatic cavities.
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The shovel-like shape was similar to that of the common seagull, and the lower beak may have had a shape similar to that of this bird. The retroarticular process at the back of the jaw (where jaw muscles attached that opened the beak) was well developed and consisted mainly of the angular bone. The surangular was the largest bone of the lower jaw, which is usual in theropods. The mandibular fenestra, a sidewards-facing opening in the lower jaw, was elongated and comparatively small.
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The best known species is S. aegyptiacus from Egypt, although a potential second species, S. maroccanus, has been recovered from Morocco. The contemporary spinosaurid genus Sigilmassasaurus has also been synonymized by some authors with S. aegyptiacus, though other researchers propose it to be a distinct taxon. Another possible junior synonym is Oxalaia from the Alcântara Formation in Brazil. Spinosaurus was among the largest of all known carnivorous dinosaurs, nearly as large as or even larger than other theropods such as Tyrannosaurus, Giganotosaurus and Carcharodontosaurus.
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In the dry season it might have resorted to preying on pterosaurs. This situation resembles that in the Late Jurassic Morrison Formation of North America, which boasts up to five theropod genera over in weight, as well as several smaller genera (Henderson, 1998; Holtz and colleagues, 2004). Differences in head shape and body size among the large North African theropods may have been enough to allow niche partitioning as seen among the many different predator species found today in the African savanna (Farlow & Pianka, 2002).
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The dig site in 2002 before excavation Some paleontologists have expressed not being convinced by the conclusions of Cuesta Fidalgo, Ortega and Sanz. Mickey Mortimer pointed out the ulnar bumps appear to actually be on the anterolateral surface of the bone, rather than the posterolateral as Cuesta Fidalgo et al. claimed, and that crocodilians are a better reference than birds for reconstructing the muscles of Concavenator and other non- maniraptoran theropods. Mortimer maintained the ulnar bumps are most likely part of an intermuscular line.
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The taphonomy (burial and fossilisation process) of the three main Plateosaurus sites—Trossingen, Halberstadt and Frick—is unusual in several ways. All three sites are nearly monospecific assemblages, meaning that they contain practically only one species, which requires very special circumstances. However, shed teeth of theropods have been found at all three sites, as well as remains of the early turtle Proganochelys. Additionally, a partial "prosauropod" skeleton was found in Halberstadt that does not belong to Plateosaurus, but is preserved in a similar position.
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Tyrannosauroids were bipedal carnivores, as were most theropods, and were characterized by numerous skeletal features, especially of the skull and pelvis. Early in their existence, tyrannosauroids were small predators with long, three-fingered forelimbs. Late Cretaceous genera became much larger, including some of the largest land-based predators ever to exist, but most of these later genera had proportionately small forelimbs with only two digits. Primitive feathers have been identified in fossils of two species and may have been present in other tyrannosauroids as well.
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The nasal bones are characteristically fused, arched slightly upwards and often very roughly textured on their upper surface. The premaxillary teeth at the front of the upper jaw are shaped differently from the rest of the teeth, smaller in size and with a D-shaped cross section. In the lower jaw, a prominent ridge on the surangular bone extends sideways from just below the jaw joint, except in the basal Guanlong. Tyrannosauroids had S-shaped necks and long tails, as did most other theropods.
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The brain of Cryolophosaurus was also more primitive than those of other theropods. Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period.
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A review of the systematic position of the dinosauriform archosaur Eucoelophysis baldwini from the Upper Triassic of New Mexico, USA. Geodiversitas 28: 649-684. Martin Ezcurra obtained his Master's-level2012 – Licenciado (= Master’s degree), Universidad de Buenos Aires (Argentina) studies in 2012 at the Universidad de Buenos Aires (Argentina) with specialization in animal anatomy and systematics. As an undergraduate student, Martin conducted since 2002 research on basal dinosaurs and theropods under the advice of Dr. Fernando Novas in the Museo Argentino de Ciencias Naturales (Buenos Aires, Argentina).
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Hippodraco (lime-yellow, left) and other fauna from the Yellow Cat Member of the Cedar Mountain Formation The holotype of Hippodraco was unearthed from the Upper Yellow Cat Member of the Cedar Mountain Formation. Contemporaneous fauna from the Upper Yellow Cat include the fellow ornithopod Cedrorestes, sauropods (Cedarosaurus and Moabosaurus), theropods (Martharaptor and Nedcolbertia), the nodosaurid Gastonia, and the giant dromaeosaurid Utahraptor. Other dromaeosaurids with fragmentary remains are also known from the formation: an indeterminate eudromaeosaur (UMNH VP 20209) and an indeterminate velociraptorine (UMNH VP 21752).
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Most paleontologists have postulated that Ceratosauria split off from other theropods in the late Triassic or early Jurassic. Despite this, no ceratosaurs have been discovered prior the middle Jurassic, and even in the middle Jurassic, species are sparse. Many scientists, such as Carrano and Sampson, have postulated the lack of specimens is due to a poor fossil record, rather than an indictment on the abundance of ceratosaurs at the time. A similarly large gap of specimens exist in the lower Cretaceous, particularly for Abelisaridae.
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The nostril openings were oval and, as in all spinosaurids, positioned farther back on the skull than in typical theropods. Irritators nostrils were both proportionately and absolutely smaller than in Suchomimus and Baryonyx, but larger than those of Spinosaurus. The opening behind the orbit (eye socket), the lateral temporal fenestra, was very large, while the antorbital fenestra, in front of the eyes, was long and elliptical. The orbit itself was deep and wider at the top (where the eyeball was placed) than the bottom.
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Many spinosaurs likely had semiaquatic habits, as has been shown in studies using techniques like isotope analysis and bone histology. It has been found that they probably took advantage of aquatic prey and environments (usually marginal and coastal habitats) to occupy a distinct ecological niche, therefore avoiding competition with more terrestrial theropods. Spinosaurines appear to have been more adapted for such lifestyles than baryonychines. A 2018 study by British paleontologist Thomas M. S. Arden and colleagues examined the morphology of spinosaurine skull bones for possible aquatic traits.
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Shuangbaisaurus (meaning "Shuangbai reptile") is genus of theropod dinosaur, possibly a junior synonym of Sinosaurus. It lived in the Early Jurassic of Yunnan Province, China, and is represented by a single species, S. anlongbaoensis, known from a partial skull. Like the theropods Dilophosaurus and Sinosaurus, Shuangbaisaurus bore a pair of thin, midline crests on its skull. Unusually, these crests extended backwards over the level of the eyes, which, along with the unusual orientation of the jugal bone, led the describers to name it as a new genus.
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The of the upper jaw were lined with 15 blade-like teeth on each side in the holotype. The first eight of these teeth were very long and robust, but from the ninth tooth onward they gradually decrease in size. As typical for theropods, they featured finely edges, which in the holotype contained some 10 denticles per . Specimen MWC 1 merely showed 11 to 12, and specimen UMNH VP 5278 12 teeth in each maxilla; the teeth were more robust and more recurved in the latter specimen.
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Size of two specimens compared to a human, with holotype in green and largest known specimen in purple Dilophosaurus was one of the earliest large predatory dinosaurs, a medium-sized theropod, though small compared to some of the later theropods. It was also the largest known land-animal of North America during the Early Jurassic. Slender and lightly built, its size was comparable to that of a brown bear. The largest known specimen weighed about , measured about in length, and its skull was long.
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The crocodylomorphs Sunosuchus and Junggarsuchus are known from other localities in the "lower beds". Meanwhile, the sauropods Bellusaurus, Mamenchisaurus sinocanadorum, and Tienshanosaurus are known from the "upper beds", above the level of the tuff at 162.2 Ma, and thus were not contemporaries of Klamelisaurus. Asides from these sauropods, Aorun, and Sinraptor, the Oxfordian portion of the Shishugou Formation preserves a diverse dinosaur fauna that also includes the theropods Haplocheirus, Shishugounykus, Zuolong, Guanlong, and Limusaurus; the ornithopod Gongbusaurus; the stegosaur Jiangjunosaurus; and the marginocephalians Yinlong and Hualianceratops.
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During the Early Jurassic Period, dinosaurs such as Dilophosaurus, Anchisaurus, Coelophysis (formerly known as Megapnosaurus), and the early thyreophoran Scutellosaurus lived in North America. The latter is believed to have been the ancestor of all stegosaurs and ankylosaurs. The Middle Jurassic is the only poorly represented time period in North America, although several Middle Jurassic localities are known from Mexico. Footprints, eggshells, teeth, and fragments of bone representing theropods, sauropods, and ornithopods have been found, but none of them are diagnostic to the genus level.
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The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Brachiosaurus, Barosaurus, Diplodocus, and Apatosaurus. Dinosaurs that lived alongside Marshosaurus included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Stokesosaurus, Ornitholestes and Allosaurus, which accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web. Stegosaurus is commonly found at the same sites as Allosaurus, Apatosaurus, Camarasaurus, and Diplodocus.
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Artist's impression Eoraptor is thought to have been an omnivore, although its dentition is quite similar to that of Buriolestes, which is considered faunivorous. It was a swift sprinter and, upon catching its prey, it would use claws and teeth to tear the prey apart. Unlike later, carnivorous dinosaurs, it lacked a sliding joint at the articulation of the lower jaw, with which to hold large prey. Furthermore, only some of its teeth were curved and saw- edged, unlike those in the mouths of later theropods.
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An Ornithomimus being restrained while preyed upon by Dakotaraptor The diet of Ornithomimus is still debated. As theropods, ornithomimids might have been carnivorous but their body shape would also have been suited for a partly or largely herbivorous lifestyle. Suggested food includes insects, crustaceans, fruit, leaves, branches, eggs, and the meat of lizards and small mammals."Dromiceiomimus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs.
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The Tendaguru Beds are similar to the Morrison Formation of North America except in its marine interbeds. Kentrosaurus would have coexisted with fellow ornithischians like Dysalotosaurus lettowvorbecki; the sauropods Giraffatitan brancai, Dicraeosaurus hansemanni and D. sattleri, Janenschia africana, Tendaguria tanzaniensis and Tornieria africanus; theropods "Allosaurus" tendagurensis, "Ceratosaurus" roechlingi, "Ceratosaurus" ingens, Elaphrosaurus bambergi, Veterupristisaurus milneri and Ostafrikasaurus crassiserratus; and the pterosaur Tendaguripterus recki. Other organisms that inhabited the Tendaguru included corals, echinoderms, cephalopods, bivalves, gastropods, decapods, sharks, neopterygian fish, crocodilians and small mammals like Brancatherulum tendagurensis.
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Xixiasaurus had four closely packed teeth in each premaxilla, as in most other theropods, with roughly oval (tooth-sockets). The premaxillary teeth were smaller than the hindmost teeth of the maxilla. There was a distinct constriction between the crown and root of the premaxillary and frontmost ten maxillary teeth. The inner surfaces of the premaxillary tooth crowns were convex and the outer surfaces were somewhat concave, which created a D-shape when viewed in cross-section, a feature shared with a few other troodontids.
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Hardbound: 634 pp. This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Gryposaurus monumentensis shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaur Parasaurolophus cyrtocristatus, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Other paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians.
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A species distinction was maintained because of the age difference. This addition extended the temporal range of the genus Albertosaurus backwards by several million years and its geographic range southwards by hundreds of kilometres. Gorgosaurus libratus, which may have been a second species of Albertosaurus (A. libratus) In 2003, Philip J. Currie, benefiting from much more extensive finds and a general increase in anatomical knowledge of theropods, compared several tyrannosaurid skulls and came to the conclusion that the two species are more distinct than previously thought.
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Other predators included troodontids, oviraptorosaurs, the dromaeosaurid Saurornitholestes and possibly an albertosaurine tyrannosaur (genus currently unknown). The younger Dinosaur Park and Two Medicine Formations had faunas similar to the Oldman, with the Dinosaur Park in particular preserving an unrivaled array of dinosaurs. The albertosaurine Gorgosaurus lived alongside unnamed species of Daspletosaurus in the Dinosaur Park and Upper Two Medicine environments. Young tyrannosaurs may have filled the niches in between adult tyrannosaurs and smaller theropods, which were separated by two orders of magnitude in mass.
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Though a myriad of bones was available by 1969, many important ones were missing or hard to interpret. There were few postorbital skull elements, no femurs, no sacrum, no furcula or sternum, missing vertebrae, and (Ostrom thought) only a tiny fragment of a coracoid. Ostrom's skeletal reconstruction of Deinonychus included a very unusual pelvic bone—a pubis that was trapezoidal and flat, unlike that of other theropods, but which was the same length as the ischium and which was found right next to it.
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However, a more recent study solves this issue by suggesting a different flight stroke configuration for non-avian flying theropods. Archaeopteryx wings were relatively large, which would have resulted in a low stall speed and reduced turning radius. The short and rounded shape of the wings would have increased drag, but also could have improved its ability to fly through cluttered environments such as trees and brush (similar wing shapes are seen in birds that fly through trees and brush, such as crows and pheasants).
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Reconstructed skeleton of the therizinosaurs Falcarius utahensis and Nothronychus graffami The timeline of therizinosaur research is a chronological listing of events in the history of paleontology focused on therizinosaurs. They were unusually long-necked, pot-bellied, and large-clawed herbivorous theropods most closely related to birds. The early history of therizinosaur research occurred in three phases. The first phase was the discovery of scanty and puzzling fossils in Asia by the Central Asiatic Expeditions of the 1920s and Soviet-backed research in the 1950s.
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Inferences about behavior can also be drawn from examination of the inner ear. The semicircular canals within the inner ear aid in balance, and the lateral semicircular canal is usually parallel to the ground when the animal holds its head in an alert posture. When the skull of Majungasaurus is rotated so that its lateral canal is parallel to the ground, the entire skull is nearly horizontal. This contrasts with many other theropods, where the head was more strongly downturned when in the alert position.
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Restoration of an adult Majungasaurus, being known from many well-preserved specimens of different ages, is well studied in regards to its growth and development. Throughout ontogeny, the skull of Majungasaurus (more specifically, the jugal, postorbital, and quadratojugal) seems to have become taller and more robust; additionally, the skull bones became more fused and the eye sockets became proportionally smaller. This indicates a shift in dietary preferences between juveniles and adults. Research by Michael D'Emic et al indicates that it was among the slowest-growing theropods.
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Nevertheless, the validity of Ceratosauria was disputed throughout much of the 20th century by researchers like Romer, Lapparent, Lavocat, Colbert, and Charig. However, in 1986, more than a century after Marsh first coined the name, Jacques Gauthier revived the idea. Three years later, Rowe published a new definition of Ceratosauria, all taxa more closely related to Ceratosaurus than to birds, based on Gauthier's use of the term. This modern use of the term was thought to include the many theropods discovered since the 1880s known as coelophysoids.
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This is quite unusual compared to other theropods, which have neural spines roughly midway down their vertebrae. These genera also have long and spine-like epipophyses on the cervicals of most of the neck, although they diminish near the neck. Epipophyses are bony projections located above the postzygapophyses (joints on the rear edge of a vertebra connecting to the front edge of the following vertebra). Elaphrosaurines, on the other hand, have cervical epipophyses which are much more diminished or even absent in the case of Elaphrosaurus.
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Members of this genus could grow up to 20 feet (6.2 meters) long, although they were significantly lighter than similarly-sized carnivorous contemporaries such as Ceratosaurus. Rauhut & Carrano (2016) listed several features which could be used to diagnose Elaphrosaurinae. Elaphrosaurine cervical vertebrae are amphicoelous, meaning that both their front and rear faces are concave, particularly the front face which is quite strongly concave. While strongly concave front faces are common among many archosaurs, they are quite rare in all but the most basal theropods.
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If this identification is correct, Ostafrikasaurus represents some of the earliest known evidence of spinosaurids. The naming and distinction of new dinosaurs based solely on teeth has been frequently considered problematic by palaeontologists, such as with the debated identity of the Asian genus Siamosaurus. Buffetaut stated that with thorough comparison and analysis of morphological features such as ornamentation, theropod teeth can be sufficiently diagnostic enough to raise new taxa. Furthermore, spinosaurid teeth in particular share a unique morphology very divergent to those of other theropods.
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Further similarities between the proximal humerus of Protoavis and that of non-tetanuran theropods are found in the shared presence of an enlarged obturator ridge, whose morphology in Protoavis is again, uncannily like that observed in robust ceratosaurs, e.g., "Syntarus" kayentakatae. The resemblance between the femur of Protoavis and that of a non-tetanuran theropod becomes ever more pronounced at the distal end of the bone. Both share a crista tibiofibularis groove, a feature of a non-tetanuran theropod separating the medial and lateral condyles.
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The three best-known small theropods of the Morrison Formation — Coelurus, Ornitholestes, and Tanycolagreus — were generalized coelurosaurs, and they have been mistaken for each other at various times. Now that Coelurus and Ornitholestes have been more fully described, it is possible to distinguish them by various characteristics of their anatomy. For example, they had visibly different proportions: Coelurus had a longer back and neck than Ornitholestes, and longer, more slender legs and feet. Coelurus and Tanycolagreus are more similar, but differ in a variety of details.
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The first major re-evaluation of Proceratosaurus and its relationships was published in 2010 by Oliver Rauhut and colleagues. Their study concluded that Proceratosaurus was in fact a coelurosaur, and moreover a tyrannosauroid, a member of the lineage leading to the giant tyrannosaurs of the Late Cretaceous. Furthermore, they found that Proceratosaurus was most closely related to the Chinese tyrannosauroid Guanlong. They named the clade containing these two dinosaurs the Proceratosauridae, defined as all theropods closer to Proceratosaurus than to Tyrannosaurus, Allosaurus, Compsognathus, Coelurus, Ornithomimus, or Deinonychus.
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"A new species of the centrosaurine ceratopsid Pachyrhinosaurus from the North Slope (Prince Creek Formation: Maastrichtian) of Alaska." Acta Palaeontologica Polonica, available online 26 Aug 2011. Dinosaurs that lived alongside Einiosaurus include the basal ornithopod Orodromeus, hadrosaurids (such as Hypacrosaurus, Maiasaura, and Prosaurolophus), the ankylosaurs Edmontonia and Euoplocephalus, the tyrannosaurid Daspletosaurus (which appears to have been a specialist of preying on ceratopsians), as well as the smaller theropods Bambiraptor, Chirostenotes, Troodon, and Avisaurus. Einiosaurus lived in a climate that was seasonal, warm, and semi-arid.
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The fibula was long and narrowed towards its lower end. The metatarsus of the foot was short, massive, and consisted of five bones—four of which functioned as support elements and terminated in four toes. Functionally tetradactyl (four-toed) feet were unique to derived therizinosaurs; basal therizinosaurs and all other theropods had tridactyl feet in which the first toe was short and did not reach the ground. Externally, the metatarsus was similar to, though proportionally larger than, those of prosauropods, an early evolutionary grade of sauropodomorphs.
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Chatterjee and Majumdar thought that there was an "ecological balance" during the Carnian stage on the basis of little change in the paleofauna of the time. They considered the paleoclimate to have been warm with seasonal wet and dry seasons conducive to the growth of tropical forests. At the end of the Carnian, however, the authors claimed that many prey resources became extinct and the forest environment was replaced by a more open environment. The limited resources would have heightened competition between theropods and rauisuchids like Tikisuchus.
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Arctosaurus is an extinct genus of archosauromorph, possibly an allokotosaurian, but was often classified as a sauropodomorph dinosaur in the years to follow. Although it has also been classified as a theropod, recent review finds that the similarities it shares with theropods are spread throughout several groups of Late Triassic reptiles, and so it cannot be assigned any more specifically than to Archosauriformes. Other authors have suggested trilophosaurian affinities. Based on the size of the vertebra, a size of about in length is extrapolated.
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Therizinosauroidea was first defined by Zhang et al. in 2001, as the clade containing all theropods more closely related to Therizinosaurus than to birds. This definition, however, defines the same group as the pre- existing Therizinosauria. An alternate definition was given by Clark in 2004 (as the last common ancestor of Therizinosaurus and Beipiaosaurus and all its descendants), comprising a narrower group that excludes more primitive therizinosaurs, such as Falcarius, and allows the name Therizinosauria to remain in use for the larger group comprising all therizinosaurs.
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Tyrannosaurus and other animals of the Hell Creek Formation Several notable Tyrannosaurus remains have been found in the Hell Creek Formation. During the Maastrichtian this area was subtropical, with a warm and humid climate. The flora consisted mostly of angiosperms, but also included trees like dawn redwood (Metasequoia) and Araucaria. Tyrannosaurus shared this ecosystem with ceratopsians Leptoceratops, Torosaurus, and Triceratops, the hadrosaurid Edmontosaurus annectens, the parksosaurid Thescelosaurus, the ankylosaurs Ankylosaurus and Denversaurus, the pachycephalosaurs Pachycephalosaurus and Sphaerotholus, and the theropods Ornithomimus, Struthiomimus, Acheroraptor, Dakotaraptor, Pectinodon and Anzu.
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In 2012, Stephan Lautenschlager and colleagues analyzed the complete endocranial anatomy of Erlikosaurus and other therizinosaurs that preserve braincases. They found that therizinosaurids had well-developed senses of smell, hearing, and balance. The former two senses may have played an important role during foraging, predator evasion, and complex social behavior. These senses were also well-developed in earlier coelurosaurs and other theropods, indicating that therizinosaurs may have inherited many of these traits from their carnivorous ancestors and used them for their different and specialized dietary purposes.
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1030–1031 When flexed (bent inward) at the elbow joint to the maximum possible extent, the humerus (upper arm bone) and radius (a lower arm bone) formed a 53° angle. The ability of Ornitholestes to bend the forearm to an angle significantly more acute than 90° is characteristic of Maniraptoriformes, but absent in more primitive theropods such as Coelophysis and Allosaurus.Senter (2006), p. 1032 Even when fully extended (straightened) at the elbow, the forearm did not form a straight angle, falling short of this by 22°.
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Size of P. thomsoni (orange) compared to other small theropods Palaeopteryx (BYU 2022) has been the subject of much confusion on the internet, in the popular scientific press, and among creationist writers. It has been described as a possible bird older than Archaeopteryx, but it cannot be clearly assigned to Avialae, and its horizon is younger than that of Archaeopteryx, though it is still from the Jurassic. BYU 2022 is about long. It was described by Jensen in 1981 as an "avian – like" proximal left tibiotarsus.
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At the beginning of the Mesozoic Era, Africa was joined with Earth's other continents in Pangaea. Africa shared the supercontinent's relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are more common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an extinction event with global impact, although African strata from this time period have not been thoroughly studied.
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The specific name is derived from Latin crus, "shank", and vastator, "destroyer". The epithet, read as "Destroyer of Shins" by the naming authors, refers to a presumed defensive tactic of ankylosaurids, smashing the lower legs of attacking predatory theropods with their tail clubs. The specimen, which is stored as ROM 75860, was found in a sandstone layer of the Judith River Formation, part of the middle Coal Ridge Member with an age of between 76.2 and 75.2 million years. According to Theropoda Expeditions, it was 99% complete.
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The same pathology may have been found in a specimen of the tyrannosaurid Gorgosaurus. Remains of an unidentified theropod, which may one day turn out to be Timimus hermani or a relative, were recovered from the Strzelecki Group near Inverloch, Victoria. This specimen had a depressed fracture on the bottom of the first phalanx of its third toe. In a 2001 survey of stress fractures in theropods, one toe bone from indeterminate ornithomimids out of fifteen examined was found to have a stress fracture.
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The divot appears to be located at the origin of the deltoid or teres major muscles. The localization in theropod scapulae as evidenced by the tendon avulsion in Sue suggests that theropods may have had a musculature more complex and functionally different from those of their descendants, the birds.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.
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Feathers are sometimes referred to as “elaborate reptile scales” just as birds are sometimes viewed as a subset of reptiles instead of their own category. Although this is a simplification, it originates from bird's homology with reptiles. Birds evolved from fast bipedal dinosaurs, but feathers evolved before them, and not for flying as what was originally thought. The theory of feathers evolving for flight unraveled in the 1970s when theropod dinosaurs (some common theropods were Tyrannosaurus rex and Velociraptors) were discovered to have feathers.
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The claws of the hand are different from each other: the thumb claw is large and curved, but the other two claws are smaller and feature a straight underside. The shinbone has on its front outer side only a high narrow groove functioning as contact with the upper part of the astragalus. This processus ascendens however, though indeed positioned on the outer side, is low. Aorun is different from other theropods discovered from the same region, such as Guanlong, Haplocheirus, Limusaurus, Monolophosaurus, Sinraptor and Zuolong.
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Some other creatures from the formation include the theropods Irritator, Mirischia and Santanaraptor, and the crocodylomorph Araripesuchus. The formation also includes several turtle remains, with some specimens referring to Santanachelys, Cearachelys and Araripemys. A few fish remains were also found within the Romualdo Formation, some of which were referred to Brannerion, Rhinobatos, Rhacolepis, Tharrhias and Tribodus. The Santana Group also consists of another Lagerstätte called the Crato Formation, which is not as diverse as the Romualdo Formation, but its fossil remains are still considered important.
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Mamenchisaurus sinocanadorum When the site was first excavated, new species of turtles, crocodilians, pterosaurs, and early mammals were revealed. Many of these species showed the rudiments of characteristics that would later become their hallmarks. One of the first fossil skeletons exposed proved to be that of an unknown theropod, and revealed a stack of four more theropods buried below the first. Yang Zhongjian accompanied the first expedition to the Junggar Basin in 1928, and the fossils found included the medium-size sauropod Tienshanosaurus chitaiensis.
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Dryadissector (meaning "Dryad dissector" in Greek) is an extinct genus of varanoid lizard represented by the type species Dryadissector shilleri from the Late Cretaceous of Texas. Dryadissector is known only from isolated teeth, which may have been shed by living individuals. These teeth are common in early Campanian strata within the Aguja Formation, which date back about 80 to 82 million years. The teeth of Dryadissector are extremely similar to those of theropod dinosaurs, which led to them initially being misidentified as the remains of theropods.
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The heavy arm musculature powered sizable hand claws, that of the first digit (or "thumb") being the largest with a length of . Only the third metacarpal (long bone of the hand) is known; showing a robust morphology (form). In the pelvis, the (main hip bone) was high. The (pubic bone) had a front surface that was wider than the side surface, and its forward-facing lower end was flattened and rectangular, with a brief flange along the midline, in contrast to the expanded boot shape it had in other theropods.
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Suchomimus coexisted with other theropods like the abelisaurid Kryptops palaios, the carcharodontosaurid Eocarcharia dinops, and an unknown noasaurid. Herbivorous dinosaurs of the region included iguanodontians like Ouranosaurus nigeriensis, Elrhazosaurus nigeriensis, Lurdusaurus arenatus, and two sauropods: Nigersaurus taqueti, and an unnamed titanosaur. Crocodylomorphs were abundant; represented by the giant pholidosaur species Sarcosuchus imperator, as well as small notosuchians like Anatosuchus minor, Araripesuchus wegeneri, and Stolokrosuchus lapparenti. The local flora probably consisted mainly of ferns, horsetails, and angiosperms, based on the dietary adaptations of the large diplodocoids that lived there.
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Restoration of Buriolestes schultzi The shape of the teeth of Buriolestes suggest that it was a carnivore which fed on small vertebrates and invertebrates, which provides evidence that sauropodomorphs - and likely all saurischians and dinosaurs as a whole - were ancestrally carnivorous, and that sauropodomorphs, ornithischians, and various groups of theropods independently became herbivorous. The co-occurrence of Buriolestes and Ixalerpeton parallels the simultaneous presence of dinosaurs and non-dinosaur dinosauromorphs at other sites (such as the Ischigualasto and Chinle Formations), suggesting that, after their initial evolutionary radiation, dinosaurs did not rapidly replace their dinosauromorph precursors.
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Since the time of its discovery, Dryptosaurus has been classified in a number of theropod families. Cope (1866), Leidy (1868) and Lydekker (1888) noted obvious similarities with the genus Megalosaurus which was known at the time from remains discovered in southeastern England. Based on this line of reasoning, Cope classified it as a megalosaurid. Marsh, however, examined the remains and later assigned to its own monotypic family, Dryptosauridae. The fossil material assigned to Dryptosaurus was reviewed by Ken Carpenter in 1997 in light of the many different theropods discovered since Cope's day.
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The lower half of the third metatarsal was broad when viewed end on, partly covering the adjoining two metatarsals to each side, but narrowed abruptly at mid-length, wedging between those bones and disappearing (an arctometatarsalian foot structure). The third toe was proportionally shorter in relation to the limb than in other ornithomimids. As in other ornithomimids, the foot had no hallux (or dewclaw, the first toe of most other theropods). The unguals of the toes were flat on their lower sides; the outer two declined slightly outwards from their digits.
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Bakker's non-technical articles and books, particularly The Dinosaur Heresies, have contributed significantly to the popularization of dinosaur science. The 1988 film The Land Before Time was one of the first cinematic portrayals of theropods in the correct horizontal pose, although the tripod pose was used more often. The 1993 film version of Jurassic Park was perhaps the most significant event in raising public awareness of dinosaur renaissance theories. For the first time in a major film, dinosaurs were portrayed as intelligent, agile, warm-blooded animals, rather than lumbering monsters more common to older films.
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Scipionyx was by the describers assigned to the Coelurosauria, a group of theropods. Because the only remains recovered belong to that of a juvenile, it has proven difficult to assign this dinosaur to a more specific group. One problem is that in the build of a juvenile animal the original traits of ancestor groups are more likely to be expressed, suggesting a too basal position in the evolutionary tree. Part of the 2011 monograph was a cladistic analysis which indicated that Scipionyx was a basal member of the Compsognathidae and the sister species of Orkoraptor.
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This is confirmed with a 2017 analysis of carbon isotopes found on teeth enamels of toothed ornithocheiroids. In the analysis, they compared the enamel values of toothed ornithocheiroids with the aquatic and terrestrial consumers near the fossil site. The ornithocheirid enamels found in the Twin Mountains Formation were shown with lower enamel values compared to the aquatic consumers that lived nearby, suggesting a more terrestrial diet, similar to the carnivorous theropods found in the site. Enamels found in the Paw Paw Formation however, were described with higher values in comparison to the nearby terrestrial consumers.
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Size of the juvenile specimen compared with a human The holotype of Scipionyx represents a very small individual, the preserved length being just 237 millimetres. In 2011 dal Sasso & Maganuco estimated its total length, including the missing tail section, at 461 millimetres. The specimen was not much smaller than known embryos or hatchlings of Lourinhasaurus and Allosaurus, theropods of considerable magnitude. However, given its affinities with the Compsognathidae, it is likely that the adult size of Scipionyx did not surpass that of the largest known compsognathid, Sinocalliopteryx of 237 centimetres length.
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This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Parasaurolophus shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaur Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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Sizes are given with a range, where possible, of estimates that have not been contradicted by more recent studies. In cases where a range of currently accepted estimates exist, sources are given for the sources with the lowest and highest estimates, respectively, and only the highest values are given if these individual sources give a range of estimates. Some other giant theropods are also known; for example, a theropod trackmaker in Morocco that was perhaps between long, but the information is too scarce to make precise size estimates.
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Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth May 3, 2007; Last revised August 22, 2008; Retrieved November 9, 2009]. Recent theories propose that theropod body size shrank continuously over the past 50 million years, from an average of down to , as they eventually evolved into modern birds. This is based on evidence that theropods were the only dinosaurs to get continuously smaller, and that their skeletons changed four times faster than those of other dinosaur species.
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However, based on osteological features, in 1984 Gregory S. Paul proposed that segnosaurs were no theropods but Late Cretaceous prosauropods and they represented a transitional form between prosauropods and ornithischians. For instance, segnosaurs resembled prosauropods in their skull and foot morphology and were also similar to ornithischians in their snout, pubis, and ankle. In 1988 he suggested a segnosaurian classification for the therizinosaurids Therizinosaurus. In a review article on the book The Dinosauria in 1990, Barsbold and Teresa Maryańska considered Segnosauria to be an enigmatic group of saurischians with a position subject to change.
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This new taxon represented the most complete member and was known from multiple specimens with numerous theropod traits. Moreover, the preserved hindlimbs in some specimens showed that the assignment of segnosaurian hindlimbs to Therizinosaurus was correct and "segnosaurs" were in fact theropods. Russell and Dong also noted the extreme similarities between Therizinosauridae and Segnosauridae and considered that the latter was a synonym of the former due to priority. However, Alxasaurus was a fairly more primitive genus and the superfamily Therizinosauroidea was coined to contain it and related species.
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They were relatively small-sized therizinosaurs, measuring long and weighing about in contrast to the advanced and giant Segnosaurus or Therizinosaurus. The necks of Beipiaosaurus were shorter than in most therizinosaurs, whose are characterized by elongated necks adapted for high-browsing. Also, their feet configuration differs from therizinosaurids, having a generic three-toed pes instead of four as seen in other members. The exact classification of therizinosaurs had in the past been hotly debated, since their prosauropod- like teeth and body structure indicate that they were generally herbivorous, unlike typical theropods.
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The tail was also covered in feathers between four and seven centimeters long, consisting of parallel filaments with a width of , without a trace of pennaceous feathers or a tail fan, as indicated by the preserved pygostyle. Unique among known theropods, Beipiaosaurus also possessed a secondary coat of much longer, simpler feathers that rose out of the down layer. These unique feathers known as EBFFs (elongated broad filamentous feathers) were first described by Xu et al. 2009, based on specimen STM 31-1 consisting of the torso, head and neck.
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All carnivorous dinosaurs (certain types of theropods) are traditionally classified as saurischians, as are all of the birds and one of the two primary lineages of herbivorous dinosaurs, the sauropodomorphs. At the end of the Cretaceous Period, all saurischians except the birds became extinct in the course of the Cretaceous–Paleogene extinction event. Birds, as direct descendants of one group of theropod dinosaurs, are a sub-clade of saurischian dinosaurs in phylogenetic classification. Saurischian dinosaurs are traditionally distinguished from ornithischian dinosaurs by their three- pronged pelvic structure, with the pubis pointed forward.
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Oxalaia quilombensis is the eighth officially named theropod species from Brazil and the largest carnivorous dinosaur discovered there. It is closely related to the African genus Spinosaurus, and/or may be a junior synonym of this taxon. Although Oxalaia is known only from two partial skull bones, Kellner and colleagues found that its teeth and had a few distinct features not seen in other spinosaurids or theropods, including two replacement teeth in each socket and a very sculptured secondary palate. Oxalaia habitat was tropical, heavily forested, and surrounded by an arid landscape.
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In 1969, John Ostrom described Deinonychus antirrhopus, a theropod that he had discovered in Montana in 1964 and whose skeletal resemblance to birds seemed unmistakable. Ostrom became a leading proponent of the theory that birds are direct descendants of dinosaurs. Further comparisons of bird and dinosaur skeletons, as well as cladistic analysis strengthened the case for the link, particularly for a branch of theropods called maniraptors. Skeletal similarities include the neck, the pubis, the wrists (semi-lunate carpal), the 'arms' and pectoral girdle, the shoulder blade, the clavicle and the breast bone.
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The external naris was large and located in a hindwards position, similar to tetanuran theropods. The orbit was large, while the lateral temporal fenestra was not as large as would be expected from more derived (or "advanced") members of the Ceratosauria. Uniquely to Limusaurus, the inner bottom edge of the premaxilla, the frontmost bone of the upper jaw, was convex. The nasal bone was distinct in having a "shelf" on its side, was short, wide, less than one third of the length of the , and twice as long as it was wide.
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The early halt in tooth replacement possibly resulted from the regression of the replacement tooth buds during the first year, as in the veiled chameleon. The replacement of teeth by a beak during growth in Limusaurus suggests that beaks in other lineages of theropods, and indeed beaked animals in general, may have evolved heterochronically, i.e. that beaks first occurred in adults and then gradually extended to juveniles. This is in accordance with genetic signal pathways (molecular processes that control the formation of teeth) still being present in birds.
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It was once thought to be closely related to modern birds, but the 2019 discovery of a pelvis from what was Hateg Island (present-day Romania) shows several primitive features. Its femur shows that it was a graviportal form rather than cursorial, not adapted for running. Due to fragmentary remains, many aspects of its biology and ecology are unknown, such as its diet. It coexisted with large predators like abelisaurid theropods, herbivores such as ankylosaurians and titanosaurian sauropods, as well as pterosaurs, crocodylomorphs, turtles, fish, and various archaic birds.
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Memorie 37: 1–281. . Sinocalliopteryx feeding on Confuciusornis In addition to the dromaeosaurid leg, four irregularly-shaped stones with a diameter between fifteen and twenty millimetres were found in the abdomen, with no similar stones present in any other portions of the skeleton or embedded in the surrounding rock. The authors interpreted these as gastroliths (gizzard stones) similar to those found with Nqwebasaurus and Baryonyx. Other theropods, such as Caudipteryx and a Mongolian ornithomimid, were also found with gastroliths, though in those cases the stones were much more numerous and smaller in size.
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An indeterminate Carcharodontosaurus species is known from the deposits, along with other small-to-medium-sized theropods, and the mesoeucrocodylian Coringasuchus anisodontis. The paleoecological situation in Cenomanian Brazil highly resembles that of Middle Cretaceous north Africa, particularly the Kem Kem and Bahariya Formations; many of the same biota can be found in both north Africa and northeastern Brazil. This is a result of Gondwana, a supercontinent that comprised Africa and South America, after their separation, the taxa on each landmass would have continued to evolve separately; contributing to small anatomical differences between the transoceanic taxa.
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However, newer finds revealed a diverse contemporary sauropodomorph fauna with six additional species, including Ignavusaurus, Arcusaurus and two unnamed taxa as well as two unnamed sauropods. It is not clear which carnivores may have preyed on Massospondylus. Most of the theropods that have been discovered in rocks of Early Jurassic age in southern Africa, such as Coelophysis, were smaller than mid-sized sauropodomorphs like Massospondylus. These smaller predators have been postulated as using fast slashing attacks to wear down sauropodomorphs, which could have defended themselves with their large hand and foot claws.
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Holtz (1994) defined the clade Arctometatarsalia as "the first theropod to develop the arctometatarsalian pes and all of its descendants." This group included the Troodontidae, Tyrannosauroidea, and Ornithomimosauria. Holtz (1996, 2000) later refined this definition to the branch-based "Ornithomimus and all theropods sharing a more recent common ancestor with Ornithomimus than with birds." Subsequently, the idea that all arctometatarsalian dinosaurs formed a natural group was abandoned by most paleontologists, including Holtz, as studies began to demonstrate that tyrannosaurids and troodontids were more closely related to other groups of coelurosaurs than they were to ornithomimosaurs.
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Orkoraptor was originally classified as Maniraptora incertae sedis. While the majority of phylogenetic trees recovered in its describers' analysis recovered it as a compsognathid, the describers considered this unlikely based on its much larger size and presence in much younger strata. Orkoraptor was subsequently recovered in Megaraptora, a clade including several other enigmatic medium to large theropods, which has variously been considered to be a member of Allosauroidea and Tyrannosauroidea. The phylogenetic trees in the publication of Gualicho shinyae have found megaraptorans to be either allosauroids or basal coelurosaurs.
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Spinosaurids were large bipedal carnivores. Their crocodilian-like skulls were long, low and narrow, bearing conical teeth with reduced or absent serrations. The tips of their upper and lower jaws fanned out into a spoon-shaped structure similar to a rosette, behind which there was a notch in the upper jaw that the expanded tip of the lower jaw fit into. The nostrils of spinosaurids were retracted to a position further back on the head than in most other theropods, and they had bony crests on their heads along the midline of their skulls.
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C. rhodesiensis was a lean, elongated species of theropod dinosaur with an S shaped neck, long hind limbs that resembled the legs of large birds such as the Secretarybird, shorter forelimbs with four digits on each hand unlike most later theropods, and a long tail. While still lean, it sported a more robust frame than other Coelophysoidea members. Its extremely bird-like body lead to C. rhodesiensis being one of the first dinosaurs to be portrayed with feathers, though there is no direct evidence that it actually had feathers.
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The dorsal ribs lack uncinate process, and the sternum is also unossified, like other troodontids. Like other theropods, the first pair of the gastralia near the front of the torso is noticeably more robust, particularly in the central portion. Similar to other paravians, the caudal vertebrae of Jianianhualong become increasingly longer towards the back of the tail; for instance, the fifteenth caudal is about twice as long as the sixth. From the twenty-third caudal backwards, the sides of the caudals become compressed such that they are sub-triangular.
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Restoration of Olorotitan and Charonosaurus in their environment O. arharensis shared its time and place with several other types of animal, including two other lambeosaurines: the Parasaurolophus-like Charonosaurus and more basal Amurosaurus. Additionally, remains from turtles, crocodilians, theropods, and nodosaurids were found at its discovery site, and the Saurolophus-like hadrosaurine Kerberosaurus is also known from roughly contemporaneous rocks in the area. Unlike the situation in North America, where lambeosaurines are virtually absent from Late Maastrichtian rocks, Asian lambeosaurines are diverse and common at the end of the Mesozoic, suggesting climatic or ecological differences.
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The regions surrounding the formation were arid to semi-arid, with most of the local flora being xerophytic (adapted to dry environments). Cycadales and the extinct conifer Brachyphyllum were the most widespread plants. Restoration of Irritator walking down a coastline in the Romualdo Formation environment This environment was dominated by pterosaurs, including: Anhanguera, Araripedactylus, Araripesaurus, Brasileodactylus, Cearadactylus, Coloborhynchus, Santanadactylus, Tapejara, Thalassodromeus, Tupuxuara, Barbosania, Maaradactylus, Tropeognathus, and Unwindia. The known dinosaur fauna besides Irritator was represented by other theropods like the tyrannosauroid Santanaraptor, the compsognathid Mirischia, an indeterminate unenlagiine dromaeosaurid, and a megaraptoran.
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Utahceratops shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, tyrannosaurids like Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Some fossil evidence suggests the presence of the Tyrannosaurid albertosaurus and the ornithomimid Ornithomimus velox, but the existing assessment of the material is not conclusive. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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Hypacrosaurus sp. skeleton exhibited in the National Museum of Nature and Science, Tokyo, Japan. H. altispinus shared the Horseshoe Canyon Formation with fellow hadrosaurids Edmontosaurus and Saurolophus, hypsilophodont Parksosaurus, ankylosaurid Anodontosaurus, nodosaurid Edmontonia, horned dinosaurs Montanoceratops, Anchiceratops, Arrhinoceratops, and Pachyrhinosaurus, pachycephalosaurid Stegoceras, ostrich-mimics Ornithomimus and Struthiomimus, a variety of poorly known small theropods including troodontids and dromaeosaurids, and the tyrannosaurs Albertosaurus and Daspletosaurus. The dinosaurs from this formation are sometimes known as Edmontonian, after a land mammal age, and are distinct from those in the formations above and below.
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Ceratosaurus gives its name to the Ceratosauria, a clade of theropod dinosaurs that diverged early from the evolutionary lineage leading to modern birds. Within the Ceratosauria, some paleontologists proposed it to be most closely related to Genyodectes from Argentina, which shares the strongly elongated teeth. The geologically older genus Proceratosaurus from England, although originally described as a presumed antecedent of Ceratosaurus, was later found to be unrelated. Ceratosaurus shared its habitat with other large theropod genera including Torvosaurus and Allosaurus, and it has been suggested that these theropods occupied different ecological niches to reduce competition.
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In addition, the large size of these theropods would have tended to decrease competition, as the number of possible prey items increases with size. Foster and Daniel Chure, in a 2006 study, concurred with Henderson that Ceratosaurus and Allosaurus generally shared the same habitats and preyed upon the same types of prey, thus likely had different feeding strategies to avoid competition. According to these researchers, this is also evidenced by different proportions of the skull, teeth, and fore limb. The distinction between the two Allosaurus morphs, however, was questioned by some later studies.
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A pair of small, pyramid-shaped structures rise up out of the astragalus, one in front of the facet for the tibia, and the other behind it. The one in front is similar to a structure found in dinosauriform ankles known as the anterior ascending process, and it may be homologous with it. However, the posterior ascending process (the one behind the tibial facet) is entirely unique to lagerpetids. The rear of the astragalus lacks a horizontal groove, similar to Tropidosuchus, theropods, and ornithischians, but unlike most other archosauriforms.
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As the name suggests, it is best known for the high neural spines on many of its vertebrae, which most likely supported a ridge of muscle over the animal's neck, back, and hips. Acrocanthosaurus was one of the largest theropods, reaching in length, and weighing up to . Large theropod footprints discovered in Texas may have been made by Acrocanthosaurus, although there is no direct association with skeletal remains. Recent discoveries have elucidated many details of its anatomy, allowing for specialized studies focusing on its brain structure and forelimb function.
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At the time of its discovery, Acrocanthosaurus and most other large theropods were known from only fragmentary remains, leading to highly variable classifications for this genus. J. Willis Stovall and Wann Langston Jr. first assigned it to the "Antrodemidae", the equivalent of Allosauridae, but it was transferred to the taxonomic wastebasket Megalosauridae by Alfred Sherwood Romer in 1956. To other authors, the long spines on its vertebrae suggested a relationship with Spinosaurus. This interpretation of Acrocanthosaurus as a spinosaurid persisted into the 1980s, and was repeated in the semi-technical dinosaur books of the time.
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Once the prey was trapped against the body, Acrocanthosaurus may have dispatched it with its jaws. Another possibility is that Acrocanthosaurus held its prey in its jaws, while repeatedly retracting its forelimbs, tearing large gashes with its claws. Other less probable theories have suggested the forelimb range of motion being able to grasp onto the side of a sauropod and clinging on to topple the sauropods of smaller stature, though this is unlikely due to Acrocanthosaurus having a rather robust leg structure compared to other similarly structured theropods.
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Opisthocoelous cervical vertebrae from Aerosteon The cervical (neck) vertebrae of megaraptorans were nearly unique among theropods in the fact that they were strongly opisthocoelous. This means that they were convex from the front and concave from behind. Opisthocelous vertebrae are also characteristic of Allosaurus and sauropods, and they may facilitate high flexibility without sacrificing defense against shear forces. Otherwise, the cervicals were similar to those of carcharodontosaurians, with short neural spines, transverse processes (projecting rib facets) located around mid-length on the centra, and a pair of large lateral pits known as pleurocoels.
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In fact, one or more pleurocoels were present in most megaraptoran vertebrae, and they connected to a complex system of numerous small air pockets within the vertebrae. This web-like internal structure of megaraptoran vertebrae (and that of a few other theropods) has been described as "camellate". The proximal caudals (vertebrae at the base of the tail) had a longitudinal ridge running along their lower surface, similar to the case in Neovenator but unlike tyrannosauroids. They also had a pair of lateral ridges which stretched downwards from the transverse processes to the centra.
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Other pterosaurs from the Romualdo Formation include Anhanguera, Araripedactylus, Araripesaurus, Brasileodactylus, Cearadactylus, Coloborhynchus, Santanadactylus, Tapejara, Tupuxuara, Barbosania, Maaradactylus, Tropeognathus, and Unwindia. Thalassodromines are only known from this formation, and though well-preserved postcranial remains from there have been assigned to the group, they cannot be assigned to genus due to their lack of skulls. Dinosaur fauna includes theropods like Irritator, Santanaraptor, Mirischia, and an indeterminate unenlagiine dromaeosaur. The crocodyliforms Araripesuchus and Caririsuchus, as well as the turtles Brasilemys, Cearachelys, Araripemys, Euraxemys, and Santanachelys, are known from the deposits.
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The hands had four fingers; the first was short but strong and bore a large claw, the two following fingers were longer and slenderer with smaller claws; the fourth was vestigial. The thigh bone was massive, the feet were stout, and the toes bore large claws. Dilophosaurus is a member of the family Dilophosauridae along with Dracovenator, a group placed between the Coelophysidae and later theropods. Dilophosaurus would have been active and bipedal, and may have hunted large animals; it could also have fed on smaller animals and fish.
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On this occasion, Dal Sasso provisionally gave the dinosaur, now thought to be a species new to science, the Italian name Saltriosauro. Although this has been occasionally Latinised to "Saltriosaurus", even in the scientific literature, in both the Italian and Latin form it remained an invalid nomen nudum. In December 2018, Dal Sasso, Simone Maganuco and Andrea Cau named and described the specimen as the type species Saltriovenator zanellai. The generic name combines a reference to Saltrio with Latin, venator, "hunter", a common suffix in the names of theropods.
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Restoration of Saltriovenator Because of the fragmentary nature of the remains, it was impossible to directly measure the size of the animal. The describing authors therefore compared the fossils with those of two theropods of a roughly similar volume. Comparing with the skeletal elements of MOR 693, an Allosaurus fragilis specimen, they conservatively concluded that the Saltriovenator holotype individual was at least seven to eight metres long. This would make Saltriovenator the largest known theropod living before the Aalenian stage, 25% longer than Ceratosaurus from the late Jurassic.
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Despite his acknowledgment that some of the smaller Jurassic theropods had many similarities to Archaeopteryx and modern birds, he determined that they were unlikely to be direct bird ancestors and that they were instead closely–related offshoots,Ries (2007) pp. 1–19. and concluded that the similarities were a result of convergent evolution rather than direct ancestry.Alexander & Vogel (2004) p. 197. Based essentially on a process of elimination, Heilmann arrives at the conclusion that birds must be descended from thecodonts, a group of archosaurs that lived during the Permian and Triassic periods.
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One consistently confounding issue Heilmann had encountered in his research into the bird-reptile link was that modern birds possess a wishbone and theropod dinosaurs, by his observations, did not. Since ancient reptilian fossils that predated dinosaurs clearly possessed a different sort of wishbone, Heilmann concluded that this feature could not have been lost and regained again over the course of evolution. Based on this law, he therefore rejected the possibility of a direct theropod ancestor of birds, though he acknowledged that theropods and birds must have shared a close relationship.Heilmann (1926) pp. 139.
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This model has also had many adherents over the years, including John Ostrom and Jacques Gauthier. The arboreal hypothesis was popular in Heilmann's day, even prior to his research, as it had been advanced by Marsh. It fell out of favor following Ostrom's research in the 1960s and 1970s, which suggested that the ancestors of birds were fast–running bipedal animals, lending credence to the cursorial model. The focus shifted back to the arboreal model when several Chinese non–avian theropods from the Early Cretaceous were found in the early 2000s.
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In a 2001 study conducted by Bruce Rothschild and other paleontologists, fifty foot bones referred to Struthiomimus were examined for signs of stress fracture, but none were found.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336. Struthiomimus was one of the first theropods envisioned from the outset as having a horizontal posture. Osborn in 1916 let the animal intentionally be depicted with an elevated tail.
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Ruben has questioned for many years the theory that birds descend from small carnivorous dinosaurs of suborder Theropoda. He suggest theropods had a diaphragma driven respiratory system which could not have evolved into the complex air sacs in birds (but the presence of air sacs in saurischian dinosaurs has been demonstrated by highly pneumatic fossil bones of e.g. Aerosteon and Tataouinea). While some have claimed Ruben's research to be flawed, his papers have, nevertheless, appeared in highly regarded, heavily peer-reviewed journals such as Science, Nature and the Journal of Morphology.
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Metatarsal II is straight, with a flattened proximal portion and boxy distal portion. Metatarsal IV has a more irregularly-shaped distal portion but is also straight, an unusual feature more akin to Lagerpeton and pterosaurs rather than the more curved bone of other dinosaurs. Isolated phalanges are variable in proportions, with one having a wide proximal articulation and the rest having tall, triangular proximal articulations and more well-developed joint surfaces. Unguals are triangular in cross section and curved, though not to the extent seen in more advanced theropods.
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This is because it is a "wildcard" taxon with several equally likely positions within Saurischia. These positions may include Nhandumirim as the sister taxon to all other saurischians, as the sister taxon to Eoraptor, or as the sister taxon to all other theropods (which also includes herrerasaurids in this option). Regardless, the authors considered unlikely that Nhandumirim is particularly close to Staurikosaurus or Saturnalia. Nonetheless, the phylogenetic position of Nhandumirim was also tested in the article describing Gnathovorax cabreirai, which recovered it as a saturnaliine sauropodomorph, close-associated with Saturnalia and Chromogisaurus.
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With such a basal position, Daemonosaurus represents a lineage that extended from the earliest radiation of dinosaurs in the Middle Triassic alongside forms such as Eoraptor and Herrerasaurus from South America. A phylogenetic analysis conducted in its original description found Daemonosaurus chauliodus to be closely related to Tawa hallae, a theropod that was described from Ghost Ranch in 2009, and the Neotheropoda. Although the two theropods are closely related, Tawa was found at a quarry that is slightly older than the Whitaker Quarry at Ghost Ranch. Sues et al.
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This group of dinosaurs is better known from the Cretaceous of Asia, where forms such as Khaan mckennai, Conchoraptor gracilis and Oviraptor philoceratops have been discovered. Oviraptorosaurs are characterized by a shortened snout, massive endentulous jaws and extensively pneumatized skulls, often sporting elaborate crests, the function of which remains unknown. The toothless jaws have indicate to some a diet of eggs but these theropods more likely fed on plants or small vertebrates. Evidence suggests that they were feathered and some paleontologists consider them to be true birds (see the main article Oviraptorosauria for further information).
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The Late Jurassic formations of Portugal where Allosaurus is present are interpreted as having been similar to the Morrison, but with a stronger marine influence. Many of the dinosaurs of the Morrison Formation are the same genera as those seen in Portuguese rocks (mainly Allosaurus, Ceratosaurus, Torvosaurus, and Stegosaurus), or have a close counterpart (Brachiosaurus and Lusotitan, Camptosaurus and Draconyx). Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal. The three appear to have had different ecological niches, based on anatomy and the location of fossils.
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Skull cast at the Geological Museum in Copenhagen The massive skull of Albertosaurus, which was perched on a short, S-shaped neck, was about long in the largest adults. Wide openings in the skull (fenestrae) reduced the weight of the head while also providing space for muscle attachment and sensory organs. Its long jaws contained, both sides combined, 58 or more banana-shaped teeth; larger tyrannosaurids possessed fewer teeth; Gorgosaurus had more at 62. Unlike most theropods, Albertosaurus and other tyrannosaurids were heterodont, with teeth of different forms depending on their position in the mouth.
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Larger adults had leg proportions characteristic of slower- moving animals, but not to the extent seen in other large theropods like abelisaurids or carnosaurs. The third metatarsals of tyrannosaurids were pinched between the second and fourth metatarsals, forming a structure known as the arctometatarsus. It is unclear when the arctometatarsus first evolved; it was not present in the earliest tyrannosauroids like Dilong, but was found in the later Appalachiosaurus. This structure also characterized troodontids, ornithomimids and caenagnathids, but its absence in the earliest tyrannosauroids indicates that it was acquired by convergent evolution.
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Tyrannosaurids, like their tyrannosauroid ancestors, were heterodont, with premaxillary teeth D-shaped in cross section and smaller than the rest. Unlike earlier tyrannosauroids and most other theropods, the maxillary and mandibular teeth of mature tyrannosaurids are not blade-like but extremely thickened and often circular in cross-section, with some species having reduced serrations. Tooth counts tend to be consistent within species, and larger species tend to have lower tooth counts than smaller ones. For example, Alioramus had 76 to 78 teeth in its jaws, while Tyrannosaurus had between 54 and 60.
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Tratayenia has five sacral (hip) vertebrae, as is the norm for theropods. They are very similar to the dorsal vertebrae in various aspects, such as the presence of large pleurocoels, tall and narrow centra, and laminae-bound excavations below the transverse processes. However, they only have a single autapomorphy: the anteroposterior (front-to-back) width of the neural spine increases drastically in the second to fifth sacral vertebrae compared to the first vertebra. In fact, the fifth sacral's neural spine is twice as long anteroposteriorly than that of the first.
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Pneumatization of the ilium is most common in megaraptorans among theropods, as seen in taxa such as Aerosteon and Murusraptor. The outer surface of the ilium is perforated by several pneumatic pores, similar to that of Aerosteon, but the upper edge of the bone is straight, in contrast with the curved ilium of Aerosteon. A bone identified as the pubic boot (expanded tip of the pubis) has been found in the holotype, as well as fragments of the ischium, which has the form of a long, thin shaft covered in grooves.
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Life restoration Phylogenetically, Gualicho presents two possibilities; that megaraptorans and neovenatorids were carnosaurs, or that megaraptorans and neovenatorids were a grade of theropods more closely related to coelurosaurs than to carnosaurs. The cladogram below follows a 2016 analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri, and Peter J. Makovicky. The cladogram below follows the strict consensus (average result) of the twelve most parsimonious trees (the simplest evolutionary paths, in terms of the total amount of sampled features evolved or lost between sampled taxa) found by Porfiri et al. (2018)'s phylogenetic analysis.
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Most paleontologists regard birds as the only surviving dinosaurs (see Origin of birds). It is thought that all non-avian theropods became extinct, including then-flourishing groups such as enantiornithines and hesperornithiforms. Several analyses of bird fossils show divergence of species prior to the K–Pg boundary, and that duck, chicken, and ratite bird relatives coexisted with non-avian dinosaurs. Large collections of bird fossils representing a range of different species provides definitive evidence for the persistence of archaic birds to within 300,000 years of the K–Pg boundary.
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When originally named, Halszka Osmólska and Ewa Roniewicz, found that Deinocheirus was a carnosaurian, and because of its extremely unusual arms, named the monotypic family Deinocheiridae for it. Osmólska and Roniewicz found that Deinocheiridae could be placed within the superfamily Megalosauroidea, within the infraorder Carnosauria (Carnosauria at the time was a paraphyletic group of all large theropods). Previously, the only carnosaurian from that time and place in Asia was the tyrannosaurid Tarbosaurus. Osmólska and Roniewicz diagnosed Deinocheiridae, based on the only genus of the time in the family, Deinocheirus.
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Suggestions that the Triassic Coelophysis was a cannibal have been recently disproven, leaving Majungasaurus as the only non-avian theropod with confirmed cannibalistic tendencies, although there is some evidence that cannibalism may have occurred in other species as well. It is unknown if Majungasaurus actively hunted their own kind or only scavenged their carcasses. However, some researchers have noted that modern Komodo monitors sometimes kill each other when competing for access to carcasses. The lizards will then proceed to cannibalize the remains of their rivals, which may suggest similar behavior in Majungasaurus and other theropods.
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It would make sense for Noasauridae (the sister taxa to Abelisauridae) to have evolved during the Jurassic, meaning that the early appearance of elaphrosaurines would not preclude a within Noasauridae. In 2016, a redescription of Elaphrosaurus by Oliver Rauhut and Matthew Carrano argued against earlier hypotheses that elaphrosaurines were basal ceratosaurs, instead placing them alongside noasaurines within a monophyletic Noasauridae. This study formally defined Elaphrosaurinae as "all noasaurids more closely related to Elaphrosaurus than to Noasaurus, Abelisaurus, Ceratosaurus, or Allosaurus". Generally speaking, elaphrosaurines were lightly built theropods, with small skulls and long necks and legs.
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A specimen of the Mongolian oviraptorid Citipati osmolskae was discovered in a chicken-like brooding position in 1993, which may indicate that they had begun using an insulating layer of feathers to keep the eggs warm. A dinosaur embryo (pertaining to the prosauropod Massospondylus) was found without teeth, indicating that some parental care was required to feed the young dinosaurs. Trackways have also confirmed parental behavior among ornithopods from the Isle of Skye in northwestern Scotland. However, there is ample evidence of precociality or superprecociality among many dinosaur species, particularly theropods.
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Zanno in 2010 recovered Coelurus as a basal maniraptoran. Coelurus is sometimes put into its own family, Coeluridae, although the membership of the family has not been stable. Before the use of phylogenetic analyses, Coeluridae and Coelurosauria were taxonomic wastebaskets used for small theropods that did not belong to other groups; thus, they accumulated many dubious genera. As late as the 1980s, popular books recognized over a dozen "coelurids", including such disparate forms as the noasaurid Laevisuchus and the oviraptorosaurian Microvenator, and considered them descendants of the coelophysids.
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However, recent analyses in 2017 have found the genus to be undiagnostic and referred some of these specimens to the genus Stenonychosaurus (long believed to be synonymous with Troodon) and others to the newly created genus Latenivenatrix. The genus name is Greek for "wounding tooth", referring to the teeth, which were different from those of most other theropods known at the time of their discovery. The teeth bear prominent, apically oriented serrations. These "wounding" serrations, however, are morphometrically more similar to those of herbivorous reptiles, and suggest a possibly omnivorous diet.
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In 1986, Buffetaut and Ingavat classified Siamosaurus as a theropod because of the straight tall crown and double sideways recurvature of its teeth. At the time, Siamosauruss particular combination of dental characteristics, especially the longitudinal fluting and lack of serrations, had not been observed in other theropods. The authors noted similarities in Siamosauruss teeth to those of ceratosaurian tooth crowns, some of which also have longitudinal flutes. However, this identification was ruled out, since ceratosaur teeth are more narrow and blade-like in cross section, bear far fewer dental flutes, and have distinct serrations.
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The maxilla and premaxilla of Baryonyx fit together in a complex articulation, and the resulting gap between the upper and lower jaw is known as the . A downturned premaxilla and a sigmoid lower margin of the upper tooth row was also present in distantly related theropods such as Dilophosaurus. The snout had extensive (openings), which would have been exits for blood vessels and nerves, and the maxilla appears to have housed sinuses. Reconstruction of the holotype skull, Museon, The Hague Baryonyx had a rudimentary , similar to crocodiles but unlike most theropod dinosaurs.
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Medium-sized omnivorous aetosaurs and cynodonts were also present. Dinosaurs were represented by the Herrerasaurids, which include Staurikosaurus, and the basal sauropodomorph Saturnalia. The contemporaneous occurrence of basal theropods Staurikosaurus, Herrerasaurus, and Eoraptor with the ornithischian Pisanosaurus suggests that the main carnivorous and herbivorous lineages were established during the middle part of the Carnian stage. A U-Pb (uranium decay) dating found that the Santa Maria Formation dated around 233.23 million years ago, putting it 1.5 million years older than the Ischigualasto Formation, and making the two formations approximately equal as the earliest dinosaur localities.
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The lower jaw was down-turned at the front and the teeth were distinct in having additional as well as third cutting edges in some of the hindmost teeth. The forelimbs were robust and had three fingers which bore large claws, and the feet had four toes supporting the foot—apart from therizinosaurs, all theropods had three-toed feet. The front of the pelvis was adapted to support the enlarged belly. The pubic bone was turned backwards, a feature that is only seen in birds and the dinosaurs most closely related to them.
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The affinities of Segnosaurus were originally obscure and it received its own theropod family, Segnosauridae, and later when related genera were identified, an infraorder, Segnosauria. Alternative classification schemes were proposed until more complete relatives were described in the 1990s, which confirmed them as theropods. The new fossils also showed Segnosauridae was a junior synonym of the earlier named family Therizinosauridae. Segnosaurus and its relatives are thought to have been slow-moving animals that, as indicated by their unusual features, were mainly herbivorous, whereas most other theropod groups were carnivorous.
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Eusauporoda are also hypothesized to have a semi-digitigrade foot posturem demonstrated by footprint evidence. Paleontologist Jeffrey Wilson explains that eusauropods differ from theropods and prosauropods that have digitigrade pes where their heel and metatarsals are lifted off the ground. Eusauropods show asymmetry in their metatarsal shaft diameters where metatarsal I is broader than the others, suggesting that their weight was mostly assumed by their inner feet. According to Steven Salisbury and Jay Nair, basal eusauropods retain four pedal unguals but reduce their phalangeal number in their fourth digit to three units.
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The specimens discovered included an incomplete skeleton of an abelisaurid, catalogued as MPCA-Pv 815, which comprises a ; , , and vertebrae; ; and a badly-preserved . Motta and colleagues recognized that this abelisaurid, along with a coelurosaur and carcharodontosaurid, present distinct traits (autapomorphies) from other Huincul Formation theropods. The abelisaurid was formally named in 2020 by Mauricio Cerroni and colleagues as Tralkasaurus cuyi; the generic name is formed from "tralka", the Mapudungun word for "thunder", and the suffix -saurus, meaning lizard, while the specific name refers to the village of El Cuy.
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Numerous theropods are known from the Violante Farm fossil site, including Gualicho and Aoniraptor (which may or may not represent the same megaraptoran); the carcharodontosaurid Taurovenator; a coelurosaur (identified by Cerroni and colleagues as an unenlagiine) and another carcharodontosaurid that remain unnamed, but are likely distinct species; and another indeterminate megaraptoran. Other dinosaurs also include a titanosaurian sauropod and an ornithopod. Additional vertebrates from the Violante Farm site include the eilenodontid rhynchocephalian Patagosphenos; a crocodyliform, possibly belonging to the Neosuchia; a squamate; a chelid turtle; and a fish referred to Lepidotes.
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Therizinosaurs (once called segnosaurs) were small to giant-sized, mainly herbivorous, theropod dinosaurs that have been found across the Early to Late Cretaceous deposits in Mongolia, China and North America. Various features of the forelimbs, skull and pelvis unite these finds as both theropods and maniraptorans, close relatives to birds. The representative genus, Therizinosaurus, is derived from the Greek θερίζω (therízo, meaning scythe, reap or cut) and σαῦρος (sauros, meaning lizard). The older representative, Segnosaurus, is derived from the Latin word segnis (meaning slow) and the Greek σαῦρος (sauros, meaning lizard).
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Coeluridae is a historically unnatural group of generally small, carnivorous dinosaurs from the late Jurassic Period. For many years, any small Jurassic or Cretaceous theropod that did not belong to one of the more specialized families recognized at the time was classified with the coelurids, creating a confusing array of 'coelurid' theropods that were not closely related. Although they have been traditionally included in this family, there is no evidence that any of these primitive coelurosaurs form a natural group with Coelurus, the namesake of Coeluridae, to the exclusion of other traditional coelurosaur groups.
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CT scans published by Stephan Lautenschlager et al. 2012 focused on the skull and brain cavity of Erlikosaurus, revealing it to have a large forebrain, and suggesting it had well developed senses of balance, hearing and smell, all of which would have been useful in evading predators, finding food, or in performing complex social behavior. These senses were also well-developed in earlier coelurosaurs and other theropods, indicating that therizinosaurs may have inherited many of these features from their carnivorous ancestors and used them for their specialized dietary purposes.
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Size (in purple) compared with selected giant theropods and a human T. rex was one of the largest land carnivores of all time. One of the largest and the most complete specimens, nicknamed Sue (FMNH PR2081), is located at the Field Museum of Natural History. Sue measured long, was tall at the hips, and according to the most recent studies, using a variety of techniques, estimated to have weighed between to . A specimen nicknamed Scotty (RSM P2523.8), located at the Royal Saskatchewan Museum, is reported to measure in length.
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Skull of referred specimen IGM 100/973 According to a 2014 study published in Nature, Khaan was possibly sexually dimorphic. Two specimens, the holotype MPC-D 100/1127 and referred specimen MPC-D 100/1002, were analyzed, the dimorphic feature being in the anterior chevrons. Both specimens were of the same size and build, and thus were likely the same age, ruling out ontogeny. In MPC-D 100/1127, the anterior chevrons showed great similarity to those of other theropods, with no great expansion on the distal end.
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Overall, the Late Jurassic Tendaguru climate was subtropical to tropical with seasonal rains and pronounced dry periods. During the Early Cretaceous, the Tendaguru became more humid. The Tendaguru Beds are similar to the Morrison Formation of North America except in its marine interbeds. Giraffatitan would have coexisted with fellow sauropods like Dicraeosaurus hansemanni and D. sattleri, Janenschia africana, Tendaguria tanzaniensis and Tornieria africanus; ornithischians like Dysalotosaurus lettowvorbecki and Kentrosaurus aethiopicus; the theropods "Allosaurus" tendagurensis, "Ceratosaurus" roechlingi, "Ceratosaurus" ingens, Elaphrosaurus bambergi, Veterupristisaurus milneri and Ostafrikasaurus crassiserratus; and the pterosaur Tendaguripterus recki.
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Although most dinosaur skeletons from this area are incomplete, possibly due to the low preservation potential of forests, Thescelosaurus skeletons are much more complete, suggesting that this genus frequented stream channels. Thus when a Thescelosaurus died, it may have been in or near a river, making it easier to bury and preserve for later fossilization. Russell tentatively compared it to the capybaras and tapirs. Other dinosaurs that shared its time and place include the ceratopsids Triceratops and Torosaurus, hadrosaurid Edmontosaurus, ankylosaurid Ankylosaurus, pachycephalosaurian Pachycephalosaurus, and the theropods Ornithomimus, Troodon, and Tyrannosaurus.
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Unusually, based on its classification as an advanced theropod in the clade Pennaraptora (a group containing theropods with advanced, bird-like feathers), the feathers were all very simple in structure and "paintbrush- like", with long quill-like bases topped by sprays of thinner filaments. All these structures were rather stiff. The feathers covered most of the body, starting near the tip of the snout. The head and neck feathers were long and formed a thick coat, and the body feathers were even longer and denser, making it difficult for scientists to study their detailed structure.
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Besides Cristatusaurus lapparenti and Suchomimus tenerensis, theropods such as the abelisaurid Kryptops palaios, the carcharodontosaurid Eocarcharia dinops, and an unknown noasaurid have been found. Herbivorous dinosaurs of the region included iguanodontians like Ouranosaurus nigeriensis, Elrhazosaurus nigeriensis, Lurdusaurus arenatus, and two sauropods: Nigersaurus taqueti, and an unnamed titanosaur. Crocodylomorphs were abundant; represented by the giant pholidosaur species Sarcosuchus imperator, as well as small notosuchians like Anatosuchus minor, Araripesuchus wegeneri, and Stolokrosuchus lapparenti. The local flora probably consisted mainly of ferns, horsetails, and angiosperms, based on the dietary adaptations of the sauropods that lived there.
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However, even though the pelvic structure of Corythosaurus and other Ornithischians does bear a greater superficial resemblance to birds than the Saurischian pelvis does, birds are now known to be highly derived Maniraptoran theropods. Corythosaurus is currently classified as a hadrosaurid, in the subfamily Lambeosaurinae. It is related to other hadrosaurs such as Hypacrosaurus, Lambeosaurus and Olorotitan, with the exception of Olorotitan they all share similar looking skulls and crests. However, research published in 2003 has suggested that even though it possesses a unique crest, Olorotitan is Corythosaurus closest known relative.
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Most theropods walked with three toes contacting the ground, but fossilized footprint tracks confirm that many basal paravians, including dromaeosaurids, troodontids, and some early avialans, held the second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly. The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking). This claw was especially large and flattened from side to side in the large-bodied predatory eudromaeosaurs.
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A small minority of researchers have claimed that the simple filamentous "protofeather" structures are simply the result of the decomposition of collagen fiber under the dinosaurs' skin or in fins along their backs, and that species with unquestionable feathers, such as oviraptorosaurs and dromaeosaurs are not dinosaurs, but true birds unrelated to dinosaurs.Feduccia, A. (2012). Riddle of the Feathered Dragons: Hidden Birds of China. Yale University Press, , However, a majority of studies have concluded that feathered dinosaurs are in fact dinosaurs, and that the simpler filaments of unquestionable theropods represent simple feathers.
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Akainacephalus shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, tyrannosaurids like Teratophoneus, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Some fossil evidence suggests the presence of the tyrannosaurid Albertosaurus and the ornithomimid Ornithomimus velox, but the existing assessment of the material is not conclusive. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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This genus represents the earliest record of Gondwanan dromaeosaurids, and supports the fact that large dromaeosaurids took the role of large predators alongside abelisaurids such as Quilmesaurus. During his description of Pellegrinisaurus, Salgado suggested that large titanosaurs and theropods inhabited interior environments of the region, and contemporaneous hadrosaurids and the titanosaur Aeolosaurus inhabited coastal lowlands. The diversity among titanosaurs indicates that the Allen Formation had environments that supported a great range of herbivorous dinosaurs. Other contemporaneous paleofauna includes the titanosaurs Laplatasaurus, Rocasaurus and Saltasaurus, the bird Limenavis, and the hadrosaurids Bonapartesaurus and Lapampasaurus.
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The injuries were also found to be mostly healed. This healing may indicate that allosauroids had an intermediate metabolic rate, similar to non-avian reptiles, which means they require fewer nutrients in order to survive. A lower nutrient requirement means allosauroids do not need to undertake frequent hunts, which lowers their risk of sustaining traumatic injuries. Although the remains of other large theropods like tyrannosaurids bear evidence of fighting within their species and with other predators, the remains of allosauroids do not bear much evidence of injuries from theropod combat.
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Coria and Salgado originally found Giganotosaurus to group more closely with the theropod clade Tetanurae than to more basal (or "primitive") theropods such as ceratosaurs, due to shared features (synapomorphies) in the legs, skull, and pelvis. Other features showed that it was outside the more derived (or "advanced") clade Coelurosauria. In 1996, Sereno and colleagues found Giganotosaurus, Carcharodontosaurus, and Acrocanthosaurus to be closely related within the superfamily Allosauroidea, and grouped them in the family Carcharodontosauridae. Features shared between these genera include the lacrimal and postorbital bones forming a broad "shelf" over the orbit, and the squared front end of the lower jaw.
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In their 2006 description of the genus, Coria and Currie suggested that though this could be due to a long term or coincidental accumulation of carcasses, the presence of different growth stages of the same taxon indicated the aggregation was not coincidental. In a 2006 National Geographic article, Coria stated that the bonebed was probably the result of a catastrophic event, and that the presence of mainly medium-sized individuals, with very few young or old, is normal for animals that form packs. Therefore, Coria said, large theropods may have hunted in groups, which would be advantageous when hunting gigantic sauropods.
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A second row of openings runs parallel to the lower jaw edge and ends at the thirteenth tooth position, which is exceptionally far. At the inside of the dentary, the Meckelian groove at the level of the third tooth extends to the front into two superimposed narrow slits. The rear of the lower jaw shows a unique combination of a kinked suture between the angular and the surangular, and the basal trait of the surangular reaching the rear jaw edge. The rather small foramen surangulare posterior is not overhung by a thick bone shelf, which is rare among large theropods.
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Crocodilians are commonly found; four species are present: Elosuchus cherifiensis, a genus belonged to the Trematochampsidae, Araripesuchus rattoides and Laganosuchus maghrebensis. Rebbachisaurus garasbae coexisted with many dinosaurs, including an ornithischian and an unnamed basal theropod, both only known from footprints. Among theropods, two carcharodontosaurids (Carcharodontosaurus saharicus and Sauroniops pachytholus), one spinosaurid (Spinosaurus aegyptiacus), one coelurosaur (Deltadromeus agilis), an unnamed abelisaur and an unnamed dromaeosaur also coexist with Rebbachisaurus. Pterosaurs are also present, although their fossils are extremely rare and enigmatic: an azhdarchid, an ornithocheirid, a tapejarid and a pteranodontid are known to have coexisted with Rebbachisaurus.
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The sutures between the individual bones of the skull are only partially visible, which indicates that the holotype represents a subadult individual. This is also consistent with the state of ossification in the post-cranial skeleton. An unusual feature of the braincase is the parasphenoid recess, which has only been described in two other non-avian theropods, Sinovenator and Sinornithosaurus. Given the distant phylogenetic position of the basal tetanuran Piatnitzkysaurus and the advanced maniraptoran and deinonychosaurian taxa Sinovenator and Sinorntihosaurus, the presence of this recess represents a convergence and can be considered an autapomorphy of the former genus.
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From this it has been concluded that the habitat of Scipionyx in general consisted of small islands and it represented one of the larger animals of its ecosystem. However, there are also indications that the terranes regularly interconnected to form far more extensive islands, land bridges allowing a dispersal of much larger animals, such as sauropods and large theropods. If so, they were not present for long when the land surface fragmented again, because there are no signs of insular dwarfism, a size reduction as an adaptation to decreased resources. Likewise, Scipionyx itself is no dwarf among its relatives.
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They are amphiplatyan with an oval cross-section and bear low spines with a hexagonal profile. Just below the top of the spine on the front and back edge a small beak-shaped process is present. In 1998 interpreted as a reduced hyposphene-hypantrum complex, a system of secondary vertebral joints shown by many theropods, it was by the 2011 study seen as a pair of attachment points for tendons, as identified in 2006 in Compsognathus. Exceptionally, with the thirteenth vertebra the two rib joint processes, the parapophysis and the diapophysis, are positioned at the same level.
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These "relict" species include the compsognathid dinosaur Sinosauropteryx and the anurognathid pterosaur Dendrorhynchoides. It also has the earliest and most primitive known members of groups that spread all around the world by the Late Cretaceous, including neoceratopsians, therizinosaurs, tyrannosaurs, and oviraptorids. Northeastern Asia may have been the center of diversification of these dinosaur groups. The Jehol Biota was not entirely isolated, however, because it also includes animals which were known from all around the world at the same time, including discoglossid frogs, paramacellodid lizards, multituberculate mammals, enantiornithine birds, ctenochasmatid pterosaurs, iguanodontian ornithopods, titanosauriform sauropods, nodosaurid ankylosaurs, and dromaeosaurid theropods.
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A 2018 study by Donald Henderson, however, refutes the claim that Spinosaurus was semiaquatic. By studying the buoyancy in lungs of crocodilians and comparing it to the lung placement in Spinosaurus, it was discovered that Spinosaurus could not sink or dive below the water surface. It was also capable of keeping its entire head above the water surface while floating, much like other non- aquatic theropods. Furthermore, the study found that Spinosaurus had to continually paddle its hind legs to prevent itself from tipping over onto its side, something that extant semiaquatic animals do not need to perform.
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Genus List for Holtz 2012 Weight Information The related "Nanshiungosaurus" bohlini was similar in size (about long), however, its assignment to Nanshiungosaurus is unlikely and it may or not represent another species or specimen of the better known Suzhousaurus. Therizinosaurus were the largest representatives, reaching the top dimensions of the group, they grew up to long weighing over . These dimensions that make the genus among the largest-known theropods. The exponential sizes obtained across the Therizinosauridae appear to have been triggered by the bulk and specialized diet within the group and early members of the Therizinosauria.
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The lateral projection of the astragalus is thickened and extends to the midline of the whole element from the inner side to the rear, leading space for the lower end of the tibia; this exposes the lateral surface of the tibia in a frontal view. The calcaneum was larger and robust than most theropods. It has a rounded shape with concave articular surfaces and had a mobile articulation with the adjacent elements such as the astragalus or distal tarsals. Another highly modified element was the tetradactyl pes: the metatarsus was composed by four shortened, fully functionally metatarsals.
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Segnosaurus holotype pelvis in lateral view and metatarsus in top view as in the original description by Perle The family Therizinosauridae was coined by Evgeny Maleev in 1954 to contain the enigmatic Therizinosaurus, who interpreted this taxon as representing giant marine turtles. Relatives of Therizinosaurus were later found but not recognized as such for some time. With the description of Segnosaurus in 1979, the paleontologist Altangerel Perle coined the family Segnosauridae to contain this enigmatic taxon and tentatively considered this group to represent theropods. He noted that this new family was different from Therizinosauridae based on claw and antebrachium traits.
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Moreover, in the same year Perle and Rinchen Barsbold analyzed the pelvis structure of Segnosaurus and concluded that it was unusually different from those of "traditional" theropods. Based on these observations, they proposed that segnosaurids should be separated into a separate grouping, near the level of the main division infraorder Saurischia. Translated paper Parallel to this, the newly and also described Nanshiungosaurus was assigned to the Titanosaurinae by Dong Zhiming based on the assumption it was a sauropod genus. In the following year, both Barsbold and Perle named the new theropod infraorder Segnosauria, containing the Segnosauridae.
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The group is also notable for adaptations to the structures of their ear. The structure of their inner-ear is almost avian, with bird-like semicircular canals and an extended cochlea. For birds, an extended cochlea allows them to hear across an increased range of frequencies, suggesting a similar function in the ponderous therizinosaurids and also allowing them a good hearing and balance, which indeed, are traits better associated with carnivorous theropods. Furthermore, the lengthening of the cochlea, an adaptation which has independently evolved in a number of other theropod groups, is thought to further improve auditory acumen.
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Recovered fossils included those of turtles, crocodylomorphs, theropods and sauropods, fish, freshwater invertebrates (gastropods and bivalves), trace fossils, fragments of eggs, and plant debris. Dynamite was occasionally used to remove materials embedded in the matrix. There were expeditions to Caieira between 1949 and 1961, after which fieldwork was not continued due to a lack of new relevant findings. A series of 19 vertebrae (the last sacral and 18 caudals) found at this locality were recognized as belong to those of a titanosaur; they were initially named 'Series "C"', and subsequently became the holotype of the new genus Baurutitan (specimen number MCT 1490-R).
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Golden eagle with a European hare Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. It is usually not possible to identify tooth marks on bone made by small predatory dinosaurs due to similarities in the denticles on their teeth. However, there are exceptions, like an ornithomimid caudal vertebra that has tooth drag marks attributed to Saurornitholestes and a partial Troodon skeleton with preserved puncture marks. Small bones of small theropods that were preyed upon by larger ones may have been swallowed whole and digested frequently enough to affect their abundance in the fossil record.
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Notably, Anchiornis seems to have lacked a breastbone (sternum), which may have been made of cartilage rather than bone, as in more primitive theropods. Fossil exhibited in Japan Anchiornis has hindleg proportions more like those of more primitive theropod dinosaurs than avialans, with long legs indicating a fast-running lifestyle. However, while long legs normally indicate a fast runner, the legs and even feet and toes of Anchiornis were covered in feathers, including long feathers on the legs, similar to those in the hindwings of Microraptor. Long leg feathers on the lower legs may have slowed the running speed of Anchiornis.
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Reconstruction of Halszkaraptor escuilliei, with plumage and swimming posture based on aquatic birds that use wing-propelled swimming Halszkaraptor had characteristics that allowed it to spend time both in water and on land, including strong hindlimbs for running and smaller flipper-like forelimbs for swimming. The short tail would have brought the centre of gravity more to the front, which is more useful for swimming than walking. The torso would have been held more vertical than is normal with theropods. To this end, there are adaptations for an improved extension of the hindlimb, in the hip joint and the thighbone.
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Digitally restored skull of Erlikosaurus The well preserved jaws also allowed a study by the University of Bristol to determine how its feeding style and dietary preferences were linked to how wide they could open the mouth. In the study, performed by Lautenshlager and colleagues in 2015, it was revealed that Erlikosaurus could open its mouth to a 43 degree angle at maximum. Also included in the study for comparison were the carnivorous theropods Allosaurus and Tyrannosaurus. From the comparisons, it was indicated that carnivorous dinosaurs had wider jaw gapes than herbivores, much as modern carnivorous animals do today.
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Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence of air) in their bones. Theropods, like Aerosteon, have many air sacs in the body that are not just in bones, and they can be identified as the more primitive form of modern bird airways. Sauropods are well known for the number of air pockets in their bones (especially vertebra), although one theropod, Deinocheirus, shows a rivalling number of air pockets.
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Evolution of birds inferred as theropods evolving from the non-avian dinosaurs are represented by the Archaeopteryx (a prehistoric bird) and dinosaurs such as the Deinonychus or the Dromaeosaurus. ;Post- Mesozoic period Post-Mesozoic, representing the last 66 million years, starting with the extinction of a major part of the dinosaurs, is the Tertiary period when reptile, mammals and modern faunas evolved in that order. The Cantabrotherium truyolsi represents the deposit of Llamaquique, in Oviedo. A touch screen display provides a complete history of the last 66 million years of the evolution of the landscape and the ecosystems.
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Small fragments inside some of the remaining alveoli show that unlike its Early Cretaceous relatives Suchomimus and Cristatusaurus, Oxalaia lacked on its teeth. Apart from the single, functional tooth in each socket, there were two replacement teeth, which according to Kellner are "a common feature in sharks or in some reptiles, but not in theropods". A cross- section of the teeth showed the typical oval shape exhibited by spinosaurs rather than the lateral compression of other theropod teeth. The spinosaurid teeth reported from Laje do Coringa were classified into two primary morphotypes by Brazilian palaeontologist Manuel Medeiros in 2006.
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Stratigraphic column of the formation The formation comprises a sequence of rhythmically alternating shales and red sandstones with a minimum thickness of . The lower part of the formation was deposited under marine conditions and the upper part in a meandering river floodplain and point bar environment. Paleocurrent analysis demonstrated a flow direction towards the west, northwest and west- northwest. The formation contains ichnofossils of theropods and ornithopods, occurring in the Early Cretaceous upper part of the formation, which is marked by an angular unconformity, overlain by volcanic and clastic rocks of the Late Cretaceous to Early Paleocene Cerro Empexa Formation.
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Long filamentous structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous Yixian Formation and other nearby geological formations from Liaoning, China. These filaments have usually been interpreted as "protofeathers," homologous with the branched feathers found in birds and some non-avian theropods, although other hypotheses have been proposed. A skeleton of Dilong was described in 2004 that included the first example of feathers in a tyrannosauroid. Similarly to down feathers of modern birds, the feathers found in Dilong were branched but not pennaceous, and may have been used for insulation.
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Reconstruction of Balaur as a dromaeosaur, using the originally- proposed kicking motion Little is known about the behavior of Balaur. Because of the lack of skull material, it is impossible to determine by the shape of the teeth whether Balaur was a carnivore or a herbivore. The original description assumed it was carnivorous because it had been found that it was closely related to Velociraptor. Csiki speculated in 2010 that it may have been one of the apex predators in its limited island ecosystem, as neither the skeletons nor teeth of larger theropods have been discovered in Romania.
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Illustration showing a pack of Yutyrannus hunting Dongbeititan Because the three known individuals of Yutyrannus were allegedly found together, some paleontologists, including Xu Xing, have interpreted the animal as a pack hunter. Based on the presence of sauropod material in the quarry in which the three specimens were found, Xu has further speculated that Yutyrannus may have hunted sauropods, and that the three known individuals may have died while doing so. In addition, other sauropod hunting theropods such as Mapusaurus are known to have exhibited pack hunting behaviour. The true cause of their death, however, remains unknown.
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The completeness and articulation (connectedness) of the skeletons suggest rapid burial, though the presence of isolated body parts also suggest that some carcasses were exposed to the air for days or months. Evidence for scavenging, such as isolated bones, tooth marks on bones, or of theropods, is lacking. However, it is possible that scavengers carried whole body parts away, as feeding at the pits might not have been possible. Eberth and colleagues speculated that the two Guanlong specimens preserved at the top of pit TBB2002 could have been scavenging on the mired carcasses before getting mired themselves.
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Other dinosaurs known from the Morrison Formation include the predatory theropods Koparion, Stokesosaurus, Ornitholestes, Ceratosaurus, Allosaurus and Torvosaurus, as well as the herbivorous ornithischians Camptosaurus, Dryosaurus, Othnielia, Gargoyleosaurus and Stegosaurus. Allosaurus accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web. Ceratosaurus might have specialized in attacking large sauropods, including smaller individuals of Brachiosaurus. Other vertebrates that shared this paleoenvironment included ray-finned fishes, frogs, salamanders, turtles like Dorsetochelys, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans such as Hoplosuchus, and several species of pterosaur like Harpactognathus and Mesadactylus.
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Like virtually all other theropods, Dakotaraptor likely possessed a furcula, or “wishbone”, as part of the shoulder girdle. Theropod wishbones are quite varied and often different from the strongly U-shaped furculae most modern birds possess; the elements originally identified as the furcula of Dakotaraptor were U- to V-shaped, similar to many other dromaeosaurids such as Velociraptor, and even the large spinosaurid theropod Suchomimus. In 2015, a study by Victoria Megan Arbour et al. proposed that the presumed Dakotaraptor furculae in fact represented a part of a turtle armour, the entoplastron of Axestemys splendida, a member of the Trionychidae.
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During the Late Cretaceous, Europe was an archipelago. Southern France and north-western Spain where its fossils are found was part of the large Ibero- Armorican island in the prehistoric Tethys Sea. The rock formations that have yielded Gargantuavis fossils have also produced abundant remains of fish, turtles, crocodylomorphs, pterosaurs, various titanosaurian sauropods (including Ampelosaurus and Lirainosaurus), ankylosaurians, ornithopods, and theropods, including other early avialans, like enantiornithes. The association of abundant fossils of the ornithopod Rhabdodon, and the lack of any hadrosaurid fossils, have been used as index fossils to roughly date these formations to the late Campanian-early Maastrichtian interval.
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In all other known theropods, the second finger is the longest. At least two species, Yi and Ambopteryx, also had a long "styliform" bone growing from the wrist, which, along with the third finger, helped support a bat-like wing membrane used for gliding. This use of a long finger to support a wing membrane is only superficially similar to the wing arrangement in pterosaurs, even though it is physically more bat-like. Other features shared within the group include short and high skulls with down turned lower jaws and large front teeth, and long arms.
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When describing the first validly published specimen in 2002 (Scansoriopteryx heilmanni), Czerkas and Yuan proposed that various primitive features of the skeleton (including a primitive, "saurischian-style" pubis and primitive hip joint) showed that scansoriopterygids, along with other maniraptorans and birds, split from other theropods very early in dinosaur evolution. However, this interpretation has not been followed by most other researchers. In a 2007 cladistic analysis of relationships among coelurosaurs, Phil Senter found Scansoriopteryx to be a member of the clade Avialae. This view was supported by a second phylogenetic analysis performed by Zhang et al.
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They argued that long, grasping hands are more suited to climbing than to flight, since most flying birds have relatively short hands. Zhang et al. also noted that the foot of Scansoriopteryx is unique among non-avian theropods; while Scansoriopteryx does not preserve a reversed hallux (the backward-facing toe seen in modern perching birds), its foot was very similar in construction to primitive perching birds like Cathayornis and Longipteryx. These adaptations for grasping ability in all four limbs, the authors argued, makes it likely that Scansoriopteryx spent a significant amount of time living in trees.
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The authors concluded that the presence of stress fractures provide evidence for "very active" predation-based diets rather than obligate scavenging. Research based on energetic modelling has also backed up the role of active predatory behaviors in theropods and has effectively ruled out obligate scavenging as a likely strategy. However scavenging was still likely to have been an important resource for many theropod with body size playing a key role in its importance. In general, the researchers found that small species, such as coelurosaurs, and species larger than 1000 kg, such as an adult Tyrannosaurs rex, would have been poor scavengers.
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Angaturama (a possible synonym of Irritator) had an unusually tall crest on its premaxillae that nearly overhung the tip of the snout with a small forward protrusion. Spinosaurid nostrils were set far back on the skull, at least behind the teeth of the premaxillae, instead of at the front of the snout as in most theropods. Those of Baryonyx and Suchomimus were large and started between the first and fourth maxillary teeth, while Spinosaurus's nostrils were far smaller and more retracted. Irritator's nostrils were positioned similarly to those of Baryonyx and Suchomimus, and were between those of Spinosaurus and Suchomimus in size.
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Sigilmassasaurus ( ; "Sijilmassa lizard") is a genus of spinosaurid dinosaur that lived approximately 100 to 94 million years ago during the middle of the Cretaceous Period in what is now northern Africa. Named in 1996 by Canadian paleontologist Dale Russell, it contains a single species, Sigilmassasaurus brevicollis. The identity of the genus has been debated by scientists, with some considering its fossils to represent material from the closely related species Spinosaurus aegyptiacus, while others have classified it as a separate taxon, forming the clade Spinosaurini with Spinosaurus as its sister taxon. Sigilmassasaurus was a moderately-built, ground-dwelling, bipedal carnivore, like most other theropods.
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Like most theropods, abelisaurids were carnivorous bipeds. They were characterized by stocky hind limbs and extensive ornamentation of the skull bones, with grooves and pits. In many abelisaurids, such as Carnotaurus, the fore limbs are vestigial, the skull is shorter, and bony crests grow above the eyes. Most of the known abelisaurids would have been between 5 and 9 m (17 to 30 ft) in length, from snout to tip of tail, with a new and as yet unnamed specimen from northwestern Turkana in Kenya, Africa reaching a possible length of 11–12 m (36 to 39 ft).
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The back of the skull was more lightly built than in some other larger theropods due to extensive skull openings, yet the jaws were deep to support the proportionally large teeth. The lacrimal bone formed not only the back margin of the antorbital fenestra, a large opening between eye and , but also part of its upper margin, unlike in members of the related Abelisauridae. The quadrate bone, which was connected to the lower jaw at its bottom end to form the jaw joint, was inclined so that the jaw joint was displaced backwards in relation to the occipital condyle.
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Compared to other Morrison theropods, Ceratosaurus showed taller neural spines on the foremost tail vertebrae, which were vertical rather than inclined towards the back. Together with the deep chevron bones on the underside of the tail, they indicate a deep, "crocodile-like" tail possibly adapted for swimming. On the contrary, allosaurids feature a shorter, taller, and stiffer body with longer legs. They would have been adapted for rapid running in open terrain and for preying upon large herbivorous dinosaurs such as sauropods and stegosaurs, but as speculated by Bakker and Bir, seasonally switched to aquatic prey items when the large herbivores were absent.
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However, scientists have long considered it likely that the footprints belong to Acrocanthosaurus. A 2001 study compared the Glen Rose footprints to the feet of various large theropods but could not confidently assign them to any particular genus. However, the study noted that the tracks were within the ranges of size and shape expected for Acrocanthosaurus. Because the Glen Rose Formation is close to the Antlers and Twin Mountains Formations in both geographical location and geological age, and the only large theropod known from those formations is Acrocanthosaurus, the study concluded that Acrocanthosaurus was most likely to have made the tracks.
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The trend in the early twenty-first century to limit the material to the lectotype inspired even lower estimates, disregarding outliers of uncertain identity. Paul in 2010 stated Megalosaurus was six metres long and seven hundred kilogrammes heavy. However, the same year Benson claimed that Megalosaurus, though medium-sized, was still among the largest of Middle Jurassic theropods. Specimen BMNH 31806, a thighbone 803 millimetres long, would indicate a body weight of 943 kilogrammes, using the extrapolation method of J.F. Anderson — which method, optimised for mammals, tends to underestimate theropod masses by at least a third.
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Unlike its closest relatives, Turfanosuchus and Yonghesuchus, but convergent upon Tropidosuchus, early theropods, and the Crocodylomorpha, the lacrimal bone is as tall as the eye socket instead of being significantly shorter. Behind the eye socket, the vertical process of the jugal bone is uniquely straight. The backward process of the jugal is located underneath the forward process of the quadratojugal bone, convergent upon Erpetosuchus, Postosuchus, Polonosuchus, and the Crocodylomorpha, unlike Turfanosuchus and Yonghesuchus where they are the other way around. Furthermore, a postfrontal bone is present, with an outer process that is uniquely long and extends over the back of the eye socket.
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Excavation started in the same month and led to the recovery of a wealth of fossils in an area of approximately 200 square meters. While most fossils pertain to a new sauropod genus, remains of theropods have also been found. The sauropod material includes four fragmentary to complete individuals similar in size, together encompassing most of the skeleton, though hand and skull bones were not found except a premaxilla and teeth. In 1998, the sauropod material was briefly described as a new genus and species, Gongxianosaurus shibeiensis, in a preliminary note by palaeontologists led by He Xinlu.
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They found that the humerus of Dilophosaurus could be retracted into a position that was almost parallel with the scapula, protracted to an almost vertical level, and elevated 65°. The elbow could not be flexed past a right angle to the humerus. Pronation and supination of the wrists (crossing the radius and ulna bones of the lower arm to turn the hand) was prevented by the radius and ulna joints not being able to roll, and the palms, therefore, faced medially, towards each other. The inability to pronate the wrists was an ancestral feature shared by theropods and other dinosaur groups.
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Restoration of two Gigantoraptors protecting their nest from two Archaeornithomimus and an Alectrosaurus Gigantoraptor was unearthed from the Iren Dabasu Formation, with an existence about 95.8 ± 6.2 million years ago. During the times of the Late Cretaceous, in this area existed a large braided river valley with floodplain and fluvial environments. These environments had extensive vegetation, evidenced in the palaeosol development and the numerous herbivorous dinosaurs remains that were found in both the river channel and the floodplain sediments. Here, it lived alongside diverse dinosaurian fauna, compromising other theropods: Alectrosaurus, Archaeornithomimus, Caenagnathasia, Erliansaurus and Neimongosaurus; the sauropod Sonidosaurus, and hadrosauroids Bactrosaurus and Gilmoreosaurus.
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He postulated that as a result of this "ornithization", one or several lineages of theropods that happened to acquire the proper combination of such traits went on to evolve into actual birds. Since the identification of a number of feathered dinosaurs beginning in the late 1990s, Barsbold's ideas are more fully appreciated. When he initially published his conclusions - a list of generally rather obscure anatomical features - in 1983, there was little exchange between the Mongolian scientific community and that of Western countries. Moreover, Barsbold's early papers were usually published in Russian, in which few Western scientists are fluent.
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More directed blows would have resulted in the sides of the spikes fracturing even sturdy longbones of the legs by blunt trauma. These attacks would have crippled small and medium-sized theropods and may even have done some damage to large ones. Earlier interpretations of the defensive behaviour of Kentrosaurus included the suggestion that the animal might have charged to the rear, to run through attackers with its spines, in the way of modern porcupines. Though Kentrosaurus likely stood with forelimbs erect like in other dinosaurs, it is hypothesised that the animal adopted a sprawling posture when defending itself.
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The distinctive horns and the muscular neck may have been used in fighting conspecifics. According to separate studies, rivaling individuals may have combated each other with quick head blows, by slow pushes with the upper sides of their skulls, or by ramming each other head-on, using their horns as shock absorbers. The feeding habits of Carnotaurus remain unclear: some studies suggest the animal was able to hunt down very large prey such as sauropods, while other studies find it preyed mainly on relatively small animals. Carnotaurus was well adapted for running and was possibly one of the fastest large theropods.
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The hindmost part of the surangular had a small foramen placed in the same position as similar openings in the mandibles of non-bird theropods and modern birds. The splenial bone was three-pronged (as in some modern birds, but unlike the simple splenial of Archaeopteryx), and its lower margin followed the lower margin of the mandible. There was a large rostral mandibular fenestra and a small, rounded caudal fenestra behind it. Though only five specimens preserve parts of the beak's keratinous covering, these show that there would have been differences between species not seen in the skeleton.
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Dinosaurs known from the Morrison Formation include the theropods Allosaurus, Ceratosaurus, Ornitholestes, Saurophaganax, and Torvosaurus; the sauropods Brontosaurus, Brachiosaurus, Camarasaurus, and Diplodocus; and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Apatosaurus is commonly found at the same sites as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus. Allosaurus accounted for 70–75% of theropod specimens and was at the top trophic level of the Morrison food web. Many of the dinosaurs of the Morrison Formation are of the same genera as those seen in Portuguese rocks of the Lourinhã Formationmainly Allosaurus, Ceratosaurus, and Torvosaurusor have a close counterpartBrachiosaurus and Lusotitan, Camptosaurus and Draconyx, and Apatosaurus and Dinheirosaurus.
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The size and shape of the bite marks match the teeth of Tarbosaurus, the largest known predator from the Nemegt Formation. Various types of feeding traces were identified; punctures, gouges, striae, fragmentary teeth, and combinations of the above marks. The bite marks probably represent feeding behavior instead of aggression between the species, and the fact that bite marks were not found elsewhere on the body indicates the predator focused on internal organs. Tarbosaurus bite marks have also been identified on hadrosaur and sauropod fossils, but theropod bite marks on bones of other theropods are very rare in the fossil record.
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Because endothermy allows refined neuromuscular control, and because brain matter requires large amounts of energy to sustain, some speculate that increased brain size indicates increased activity and, thus, endothermy. The encephalization quotient (EQ) of dinosaurs, a measure of brain size calculated using brain endocasts, varies on a spectrum from bird-like to reptile-like. Using EQ alone, coelosaurs appear to have been as active as living mammals, while theropods and ornithopods fall somewhere between mammals and reptiles, and other dinosaurs resemble reptiles. A study published by Roger Seymour in 2013 added more support to the idea that dinosaurs were endothermic.
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In the clade Deinonychosauria, the continued divergence of feathers is also apparent in the families Troodontidae and Dromaeosauridae. Branched feathers with rachis, barbs, and barbules were discovered in many members including Sinornithosaurus millenii, a dromaeosaurid found in the Yixian formation (124.6 MYA). Previously, a temporal paradox existed in the evolution of feathers—theropods with highly derived bird-like characteristics occurred at a later time than Archaeopteryx—suggesting that the descendants of birds arose before the ancestor. However, the discovery of Anchiornis huxleyi in the Late Jurassic Tiaojishan Formation (160 MYA) in western Liaoning in 2009 resolved this paradox.
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Two small wings trapped in amber dating to 100 mya show plumage existed in some bird predecessors. The wings most probably belonged to enantiornithes, a diverse group of avian dinosaurs. A large phylogenetic analysis of early dinosaurs by Matthew Baron, David B. Norman and Paul Barrett (2017) found that Theropoda is actually more closely related to Ornithischia, to which it formed the sister group within the clade Ornithoscelida. The study also suggested that if the feather-like structures of theropods and ornithischians are of common evolutionary origin then it would be possible that feathers were restricted to Ornithoscelida.
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According to Kurochkin, those moderately derived theropods became extinct without leaving any descendants. He also supported the Protoavis hypothesis by Sankar Chatterjee. The Aquila kurochkini Boev 2013, an extinct eagle from Bulgaria, is named after Yevgeny Kurochkin, as is the Longusunguis kurochkini Wang, Zhou, O’Connor et Zelenkov, 2014(first described in 2014). Other bird species named after Yevgeny Kurochkin are: Anas kurochkini Zelenkov et Panteleyev, 2014, Palaelodus kurochkini Zelenkov, 2013, Zheroia kurochkini Nessov, 1988, Falco kurochkini Suárez et Olson, 2001, Glaucidium kurochkini Campbell et Bocheński, 2012, Euronyctibius kurochkini Mourer-Chauviré, 1989 and Evgenavis nobilis O'Connor et al.
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These air sacs may have allowed for a basic form of avian-style 'flow-through ventilation,' where air flow through the lungs is one-way, so that oxygen-rich air inhaled from outside the body is never mixed with exhaled air laden with carbon dioxide. This method of respiration, while complicated, is highly efficient. The recognition of pneumatic foramina in Majungasaurus, besides providing an understanding of its respiratory biology, also has larger-scale implications for evolutionary biology. The split between the ceratosaur line, which led to Majungasaurus, and the tetanuran line, to which birds belong, occurred very early in the history of theropods.
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Theropods other than Quilmesaurus were also present; they include the large unenlagiine dromaeosaurid Austroraptor, a basal ornithuran bird (Limenavis), and a cimolopterygid bird (Lamarqueavis). A tooth has been referred to the family Carcharodontosauridae; this tooth is one of the most recent carcharondontosaurid fossils found as more well known members of this family (Giganotosaurus, Mapusaurus) lived millions of years earlier in the Cretaceous. Indeterminate nodosaurid remains have also been found at this formation, consisting of vertebrae, osteoderms, a femur, and a tooth. The Allen Formation is also notable for the high amount of sauropod eggs discovered there.
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This large disparity means that it is difficult to find any skull features shared by members of Noasauridae as a whole. A skull diagram of left Noasaurids had longer arms than their relatives the abelisaurids, whose arms were tiny and diminished. Although by no means as large or specialized as the arms of advanced bird-like theropods, noasaurid arms were nevertheless capable of movement and use, possibly even for hunting in large-clawed genera such as Noasaurus. Some genera such as Limusaurus did have somewhat reduced arms and hands, but far from the extent that abelisaurids acquired.
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The humerus (upper arm bone) was thin and straight, with a low and somewhat rounded humeral head (the portion which attached to the shoulder). In contrast, abelisaurids had a large and bulbous humeral head (although similarly rounded) while that of other theropods was flattened from front to back. A skeletal diagram of Limusaurus, the most complete and well-known elaphrosaurine The leg is also somewhat characteristic in members of this family. The tibia (large innermost bone of the lower leg) was flattened from the front near the foot, although it was rounded further up the leg.
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Coelurosaurs showed a shift in the use of the forearm, with greater flexibility at the shoulder allowing the arm to be raised towards the horizontal plane, and to even greater degrees in flying birds. However, in coelurosaurs, such as ornithomimosaurs and especially dromaeosaurs, the hand itself had lost most flexibility, with highly inflexible fingers. Dromaeosaurs and other maniraptorans also showed increased mobility at the wrist not seen in other theropods, thanks to the presence of a specialized half-moon shaped wrist bone (the semi-lunate carpal) that allowed the whole hand to fold backward towards the forearm in the manner of modern birds.
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The trackway of a swimming theropod, the first in China of the ichnogenus named Characichnos, was discovered at the Feitianshan Formation in Sichuan. These new swim tracks support the hypothesis that theropods were adapted to swimming and capable of traversing moderately deep water. Dinosaur swim tracks are considered to be rare trace fossils, and are among a class of vertebrate swim tracks that also include those of pterosaurs and crocodylomorphs. The study described and analyzed four complete natural molds of theropod foot prints that are now stored at the Huaxia Dinosaur Tracks Research and Development Center (HDT).
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In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy; this approach requires that, for a group to be natural, all descendants of members of the group must be included in the group as well. Birds are thus considered to be dinosaurs and dinosaurs are, therefore, not extinct. Birds are classified as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs.
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In 2012, Buffetaut posited that this pattern would begin with large serrations in primitive Jurassic taxa like Ostafrikasaurus (from the Tithonian age), which resembled those of typical, similarly-sized theropods. These would then evolve into the fine, reduced, and more numerous serrations of Early Cretaceous baryonychines, like Baryonyx from the Barremian of Europe, and Suchomimus from the Aptian to Albian of West Africa. Baryonyx, for example, had seven denticles per mm (0.04 in) in comparison to Ostafrikasaurus's two to four. Finally, the denticles would disappear entirely in spinosaurines such as Spinosaurus from the Albian to Turonian of North Africa.
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Life restoration Most analyses place Afrovenator within the Megalosauridae, which was formerly a "wastebasket family" which contained many large and hard-to-classify theropods, but has since been redefined in a meaningful way, as a sister taxon to the family Spinosauridae within the Megalosauroidea. A 2002 analysis, focused mainly on the noasaurids, found Afrovenator to be a basal megalosaurid. However, it did not include Dubreuillosaurus (formerly Poekilopleuron valesdunensis), which could affect the results in that region of the cladogram (Carrano et al. 2002). Other more recent and more complete cladistic analyses show Afrovenator in a group of Megalosauridae with Eustreptospondylus and Dubreuillosaurus.
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Coelurus ( ) is a genus of coelurosaurian dinosaur from the Late Jurassic period (mid-late Kimmeridgian faunal stage, 155–152 million years ago). The name means "hollow tail", referring to its hollow tail vertebrae (Greek κοῖλος, koilos = hollow + οὐρά, oura = tail). Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned.
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A second species, A. altai, known from a much more complete skeleton, was named and described by Stephen L. Brusatte and colleagues in 2009. Its relationships to other tyrannosaurid genera are unclear, with some evidence supporting a hypothesis that Alioramus is closely related to the contemporary species Tarbosaurus bataar. Alioramus were bipedal like all known theropods, and their sharp teeth indicate that they were carnivores. Known specimens were smaller than other tyrannosaurids like Tarbosaurus bataar and Tyrannosaurus rex, but their adult size is difficult to estimate since both Alioramus species are known only from juvenile or sub-adult remains.
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Life restoration of Deinonychus antirrhopus The distinctive dromaeosaurid body plan helped to rekindle theories that dinosaurs may have been active, fast, and closely related to birds. Robert Bakker's illustration for John Ostrom's 1969 monograph, showing the dromaeosaurid Deinonychus in a fast run, is among the most influential paleontological reconstructions in history. The dromaeosaurid body plan includes a relatively large skull, serrated teeth, narrow snout (an exception being Utahraptor), and forward- facing eyes which indicate some degree of binocular vision. Dromaeosaurids, like most other theropods, had a moderately long S-curved neck, and their trunk was relatively short and deep.
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However, it is a considerably larger animal, around the size of a wild turkey, being among the largest known flying Mesozoic paravians. Another dromaeosaurid species, Deinonychus antirrhopus, may display partial flight capacities. The young of this species bore longer arms and more robust pectoral girdles than adults, and which were similar to those seen in other flapping theropods, implying that they may have been capable of flight when young and then lost the ability as they grew. The possibility that Sinornithosaurus millenii was capable of gliding or even powered flight has also been brought up several times, though no further studies have occurred.
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Most of the other hindmost tooth crowns are damaged so their complete features are unknown. The additional carina on tooth 23 appears to have been fully denticulated while the denticles were restricted to the basal side of the crown in tooth 22. Segnosaurus was unique among all known theropods in possessing triple carinae. The 14th alveolus on the right dentary of the holotype is walled over by seemingly pathological (due to injury or disease) bone growth but the teeth in that part of the dentary are damaged so it is not possible to determine how the teeth were affected by this.
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He found it unlikely but did not rule out that segnosaurs could have derived from theropods or that segnosaurs, prosauropods and ornithischians were each independently derived from early dinosaurs. David B. Norman considered Paul's idea contentious and "bound to provoke much argument" in 1985. In 1988, Paul maintained that segnosaurs were late-surviving, ornithischian-like prosauropods and proposed a segnosaurian identity for Therizinosaurus. He also placed segnosauria within Phytodinosauria, a superorder Robert Bakker had created in 1985 to contain all plant-eating dinosaurs. In a 1986 study of the inter-relationships of saurischian dinosaurs, Jacques Gauthier concluded segnosaurs were prosauropods.
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Reconstruction of selected sauropod necks, showing posture and length The skull length of the basal eusauropod, Patagosaurus is about . One of the most basal eusauropods, Shunosaurus, has two characteristic features of the eusauropod elongated neck: the incorporation of the equivalent of the first dorsal vertebra into the cervical region of the spine, and the addition of two cervical vertebra in the middle of the cervical vertebrae. Other synapomorphies of Eusauropoda includes a retracted position of the external nares. Unlike prosauropods and theropods, which have a snout with smooth, unprotruding alveolar and subnarial regions, eusauropods have snouts with “stepped anterior margins”.
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Saurornitholestes was found on both sides of the Western Interior Seaway. Alberta, the location of Saurornitholestes langstoni, had a habitat similar to the United States Middle West being plains and floodplain swamps. In its eastern range, Saurornitholestes lived alongside hadrosaurs like Eotrachodon and Hypsibema, large theropods like Appalachiosaurus and Dryptosaurus, an unidentified ornithomimosaur, and another unidentified small theropod that was likely either a dromaeosaurid or a troodontid. Saurornitholestes appears to have been the most common small theropod in Dinosaur Provincial Park, and teeth and bones are much more common than those of its more massive contemporary, Dromaeosaurus.
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Elżanowski & Wellnhofer (1993) claimed that Archaeornithoides was the closest known relative to birds or Avialae. This conclusion rested on key bird-like features; an interdigitated suture between the premaxilla and maxilla, broad palatal shelves, pneumatic sinuses, lack of interdental plates, and unserrated teeth. Since publication, though, all of these features have been discovered in new fossils of adult and/or juvenile troodonts and dromaeosaurs.Clark, James M., Norell, Mark A., Makovicky, Peter J. (2002) "Cladistic approaches to the relationships of birds to other theropods" pp.31-61 in “Mesozoic Birds: Above the Heads of Dinosaurs” Chiappe&Witmer; ed.
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The theropods Eustreptospondylus and possibly Megalosaurus are also known from the Oxford Clay Formation, but slightly younger deposits (the Middle Member). In addition, the theropod Metriacanthosaurus is from an unknown level and age in the formation. Hundreds of invertebrates are known from the marine deposits, including bivalves, gastropods, scaphopods, ammonites, teuthoids, a nautiloid, foraminifera, coelenterates, bryozoans, brachiopods, annelids, crustaceans, ostracods, cirripedes and echinoderms. Fish are known from the clades Elasmobranchii, Chimaera, and Actinopterygii, and the ichthyosaur Ophthalmosaurus, the plesiosaurs Cryptoclidus, Muraenosaurus, Tricleidus, Liopleurodon, Peloneustes, Pliosaurus and Simolestes, the crocodilians Metriorhynchus and Steneosaurus, and the pterosaur Rhamphorhynchus were all present.
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In this way, he considered segnosaurians to be to herbivorous dinosaurs what monotremes are to mammals. He did not rule out that segnosaurs could be derived from theropods, or that segnosaurs, prosauropods and ornithischians were each independently derived from early dinosaurs, but found these options unlikely. He considered the common descent of these groups as support for the idea that dinosaurs were a monophyletic (natural) group, which was contested by some paleontologists at the time (who instead thought different dinosaurs groups evolved independently from thecodonts). Paleontologist David B. Norman considered Paul's idea a contentious claim "bound to provoke much argument" in 1985.
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In 1988, Paul maintained that segnosaurs were late surviving ornithischian-like prosauropods, and proposed a segnosaurian identity for Therizinosaurus. He also placed segnosauria within Phytodinosauria, a superorder that palaontologist Robert Bakker had created in 1985 to retain all plant-eating dinosaurs. In a 1986 study of the interrelationships of saurischian dinosaurs, paleontologist Jacques Gauthier concluded that segnosaurs were prosauropods. While he conceded they had similarities with ornithischians and theropods, he proposed these featured had evolved independently. In a 1989 conference abstract about sauropodomorph interrelatonships, paleontologist Paul Sereno also considered segnosaurs as prosauropods, based on skull features.
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An avulsion injury left a divot on the humerus of Sue the T. rex, apparently located at the origin of the deltoid or teres major muscles. The presence of avulsion injuries being limited to the forelimb and shoulder in both Tyrannosaurus and Allosaurus suggests that theropods may have had a musculature more complex than and functionally different from those of birds. The researchers concluded that Sue's tendon avulsion was probably obtained from struggling prey. The presence of stress fractures and tendon avulsions in general provides evidence for a "very active" predation-based diet rather than obligate scavenging.
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Restoration José Bonaparte and colleagues, in their 1999 description of the genus, found it to be possible basal theropod and placed it in its own family, Guaibasauridae. Bonaparte and colleagues (2007) found another early Brazilian dinosaur Saturnalia to be very similar to it, and placed the two in the Guaibasauridae which was found to be a primitive saurischian group. Bonaparte found that these forms may have been "prosauropods" (primitive sauropodomorphs), or an assemblage of forms close to the common ancestor of the sauropodomorphs and theropods. Overall, Bonaparte considered that both Saturnalia and Guaibasaurus were more theropod-like than "prosauropod"-like.
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Monospecific bonebeds suggest it was gregarious, and that this behavior gave Aniksosaurus a selective advantage over competitors in its paleoenvironment. The hypothesis suggesting gregarious (social) behavior is supported by the taphonomic association of individuals from the Bajo Barreal Formation and evidence garnered from analysis of its bone histology. The authors of this study, Ibiricu, Martínez, Casal and Cerda (2013) noted that this particular assemblage is only the second known body fossil association of small, coelurosaurian theropods discovered in South America. The theropod taxa have been interpreted as gregarious are Coelophysis bauri,Colbert EH (1989) The Triassic dinosaur Coelophysis.
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Coronosaurus and Albertaceratops in environment Studies suggest that the paleoenvironment of the Oldman Formation was an ancient coastal plain.Eberth, D.A., and Hamblin, A.P., 1993 , Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and northern Montana : Canadian Journal of Earth Sciences, 30, 174‒200. In addition to remains of Coronosaurus, this formation has produced the remains of the theropods Saurornitholestes, Daspletosaurus, Troodon, Dromaeosaurus and Hesperonychus, the ceratopsids Albertaceratops, Chasmosaurus, and Anchiceratops, the hadrosaurids Brachylophosaurus, Gryposaurus, Parasaurolophus, and Corythosaurus, the thescelosaurid Albertadromeus and the ankylosaurid Scolosaurus.
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Bellatoripes and other tyrannosauripodids share a number of unique features that distinguish them from other known large theropod footprints, including a large heel pad and thick digits that lack distinct toe pads and taper in width towards the claws. Bellatoripes and other tyrannosauripodid tracks cannot be definitively assigned to Tyrannosauridae based on shared morphological traits alone, but the absence of other large theropods from the same geographical areas and stratigraphic ages precludes any other identities for the trackmakers. It is possible then that the soft- tissue features of Bellatoripes and tyrannosauripodid tracks are synapomorphies of Tyrannosauridae as a whole.
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Many of the hypothetical animals created for The New Dinosaurs ended up resembling actual Mesozoic creatures that have since been discovered. Many of the hypothetical dinosaurs featured in the book are covered in fuzzy integument, which in modern times have been discovered in dinosaurs of most groups. The tree-climbing arbrosaurs are similar to actual tree-climbing small theropods such as Microraptor (described in 2000) and the large terrestrial pterosaurs, such as the aforementioned "lank", resemble some animals in the actual pterosaur group Azhdarchidae. Peter Jackson's 2005 film King Kong featured a complete ecosystem populated with descendants of Mesozoic animals.
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Life restoration of Parksosaurus warreni Parksosaurus is known from the base of Unit 4 of the Horseshoe Canyon Formation, which dates to about 69.5 million years ago. Other dinosaur species from this same unit include the theropods Albertosaurus sarcophagus and Albertavenator curriei as well as the spike- crested hadrosaurid Saurolophus osborni, hollow-crested hadrosaurid Hypacrosaurus altispinus, and ankylosaurid Anodontosaurus lambei. Teeth of an unidentified ceratopsian species are known from the same stratigraphic level. The dinosaurs from this formation are sometimes known as Edmontonian, after a land mammal age, and are distinct from those in the formations above and below.
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Artist's impression of C. osmolskae and the unnamed Citipati species The largest Citipati were emu-sized animals and were the largest known oviraptorids until Gigantoraptor was described in 2007. In 2010 Gregory S. Paul estimated its length at 2.5 meters (8.2 ft), its weight at 75 kg (165 lbs). In 2016 Molina-Pérez and Larramendi estimated gave a greater size of 2.9 meters (9.5 ft) and 83 kg (183 lbs) with a hip height of 1.15 meters (3.8 ft). Like other oviraptorids, Citipati had an unusually long neck and shortened tail, compared to most other theropods.
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Deposited in the locality are many taxa, including a large accumulation of Europasaurus bones and individuals. At least 450 bones from Europasaurus were recovered from the Langenberg Quarry, with about 1/3 bearing tooth marks Of these tooth marks, the sizes and shapes match well with the teeth of fish, crocodilians or other scavengers, but no confirmed theropod marks. The high number of individuals present suggests that a herd of Europasaurus was crossing a tidal zone and drowned. While the dominant large-bodied animal present is Europasaurus, there is also material from a diplodocid sauropod, a stegosaurian, and multiple theropods.
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The formation has a diverse assemblage of dinosaurs including theropods such as Troodon, Albertosaurus, ornithomimids and dromaeosaurs, as well as several types of hadrosaurs, ceratopsians, ankylosaurs, and smaller ornithischians such as Orodromeus. It also includes pterodactyloid pterosaurs, Champsosaurus, turtles, lizards, and mammals. Other types of eggs from Two Medicine include Montanoolithus, Prismatoolithus levis (the eggs of Troodon formosus), some small unidentified theropod eggs, P. hirschi, Triprismatoolithus, Tubercuoolithus, Spheroolithus albertensis (eggs of Maiasaura), S. choteauensis, eggs of Hypacrosaurus, and Krokolithes. The Oldman Formation was formed by ephemeral rivers in a semi- arid environment characterized by seasonal precipitation.
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Fossil evidence also demonstrates that birds and dinosaurs shared features such as hollow, pneumatized bones, gastroliths in the digestive system, nest-building and brooding behaviors. Although the origin of birds has historically been a contentious topic within evolutionary biology, only a few scientists still dispute the dinosaurian origin of birds, suggesting descent from other types of archosaurian reptiles. Within the consensus that supports dinosaurian ancestry, the exact sequence of evolutionary events that gave rise to the early birds within maniraptoran theropods is disputed. The origin of bird flight is a separate but related question for which there are also several proposed answers.
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Because no embryos are known, the parent of Plagioolithus cannot be identified with certainty. It was formerly believed that triple-layered eggshells were unique to neognath birds, but some three- layered eggs have been found containing enantiornithines and non-avian theropods, indicating that the presence of a third layer is plesiomorphic among dinosaurs. Therefore, this trait alone cannot be used to assign P. fukuiensis to birds. However, the combination of the third layer, the thin shell, and the smooth external surface suggests that Plagioolithus belongs to a bird (though to what type of bird remains unknown).
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The vertebrate fauna is dominated by the small basal ornithopod Oryctodromeus, which dominates the vertebrate assemblage and is known from several partial skeletons. An ankylosaur, a Tenontosaurus-like iguanodontid, a hadrosaurid, dromaeosaurs, a tyrannosauroid, a possible neovenatorid allosauroid, a giant oviraptorosaur (represented by eggshell of the oogenus Macroelongatoolithus carleylei), indeterminate small theropods, possible neoceratopsians, large and small crocodilians, turtles, a variety of small mammals, and semionotid fish are known from very fragmentary remains.Krumenacker, L. J., Scofield, G., Simon, J., Varricchio, D., and Wilson, G. P., 2014a. Outcrop envy: Paleontology and taphonomy of the Wayan Formation, the Cenomanian foredeep deposits of Idaho.
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This younger, active dog's dewclaw always makes contact while running, so it wears down naturally to its proper length, as do its other claws. Double dewclaws on rear leg of dog A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows higher on the leg than the rest of the foot, such that in digitigrade or unguligrade species it does not make contact with the ground when the animal is standing. The name refers to the dewclaw's alleged tendency to brush dew away from the grass.
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The fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch. As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event approximately 66 million years ago. Dinosaurs can therefore be divided into avian dinosaurs, or birds; and non-avian dinosaurs, which are all dinosaurs other than birds. This list of dinosaurs is a comprehensive listing of all genera that have ever been considered to be non-avian dinosaurs, but this list also includes some dinosaurs which are disputed to be either avian or non- avian, as well as purely vernacular terms.
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Giganotosaurus did not have a sagittal crest on the top of the skull, and the jaw muscles did not extend onto the skull roof, unlike in most other theropods (due to the shelf over the supratemporal fenestrae). These muscles would instead have been attached to the lower side surfaces of the shelf. The neck muscles that elevated the head would have attached to the prominent supraoccipital bones on the top of the skull, which functioned like the nuchal crest of tyrannosaurs. A latex endocast of the brain cavity of Giganotosaurus showed that the brain was similar to that of the related genus Carcharodontosaurus, but larger.
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Feduccia responded by arguing that the origin of birds was a complex and as yet unresolved problem to which the theropod hypothesis as presently formulated was a simplistic answer, ignoring contrary evidence. Prum in turn responded to this paper by again criticizing Feduccia's failure to use cladistics and to specify an explicit alternative sister-group with which to ally birds. He particularly singled out Feduccia's adoption of the view that some theropod taxa are actually birds that have been mistaken for theropods through convergence associated with flight loss and secondary adoption of cursoriality. Prum argued, finally, that Feduccia's methodology and view of the origin and early evolution of birds are pseudoscientific.
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In 1988, Paul suggested that the eyeballs of ornithomimids were flattened and had minimal mobility within the sockets, necessitating movement of the head to view objects. Since their eyes faced more sideways than in some other bird-like theropods, their binocular vision would have been more limited, which is an adaptation in some animals that improves their ability to see predators behind them. Paul considered the relatively short tails, which reduced weight, and missing halluxes of ornithomimids to be adaptations for speed. He suggested that they could have defended themselves by pecking and kicking, but would have mainly relied on their speed for escape.
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The formation has produced impressive assemblages of invertebrates (including ammonites), plants, mammals, fish, reptiles (including the lizard Obamadon), marine reptiles (including the marine reptiles like mosasaurs, plesiosaurs and sea turtles), and amphibians. Notable dinosaur finds include Tyrannosaurus and Triceratops, ornithomimids as well, caenagnathids like Anzu, a variety of small theropods, pachycephalosaurs, ankylosaurs, crocodylomorphs and squamates, including various animal fossils unearthed in the Hell Creek Formation. The most complete hadrosaurid dinosaur ever found, an Edmontosaurus, was retrieved in 2000 from the Hell Creek Formation and widely publicized in a National Geographic documentary aired in December 2007. A few bird, mammal, and pterosaur fossils have also been found.
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Skeletal diagram The braincase of Piatnitzkysaurus has been reviewed in detail by Oliver Rauhut; the review constitutes one of the few detailed accounts of braincase morphology in basal theropods. Piatnitzkysaurusis the only member of Piatnitzkysauridae with cranial material preserved, for which two maxillae, a frontal, a braincase, and a partial dentary are known. Piatnitzkysaurus is among the most basal members of the tetanurans and is important for understanding not only Middle Jurassic theropod evolution in the Southern Hemisphere, but also for knowledge of character evolution at the base of tetanurae. The braincase of the holotype of Piatnitzkysaurus floresi (PVL 4073) is rather well preserved and shows no signs of deformation.
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This change was supported by similarities between Dracovenator, Dilophosaurus wetherilli and Zupaysaurus rougieri, suggesting these taxa might form their own clade sister to Dilophosauridae, although there is no definitive evidence.Yates, A. M. (2005) A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods. Sinosaurus and Crylophosaurus are also now classified as basal tetanurans. While all of the dinosaur genera once within Dilophosauridae are characterized by a distinctive cranial crest, it is thought that this distinctive trait was convergently evolved in dilophosaurids and basal tetanurans, and thus not all are necessarily derived from the same common ancestor.
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Restoration of U. comahuensis Novas and Puerta found that the pelvic region of Unenlagia, especially the form of the ilium, was very similar to that of the early bird Archaeopteryx. The shoulder girdle of Unenlagia was originally interpreted as if it was adapted for flapping, with a flat scapula positioned on top of the ribcage, making the shoulder joint point more laterally. However, in 2002 Kenneth Carpenter pointed out that this would imply that the shoulder-blade was dorsoventrally flattened instead of laterally as with other theropods and that it thus were more likely the scapula was located on the side of the ribcage.Carpenter, K. 2002.
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The only known fossil specimen of N. wangi is notable for having a large number of teeth compared to more advanced oviraptorosaurs, but the teeth in the back of the upper jaw (maxilla) are still reduced in number compared to most other non-avialan theropods. The reduced number of maxillary teeth in Ningyuansaurus is shared with the scansoriopterygids and other basal oviraptorosaurs such as Incisivosaurus. Though the skull is poorly preserved, the specimen preserved at least 14 teeth in the lower jaw (dentary) and 10 teeth in the upper jaw, four in the premaxilla and six in the maxilla. The teeth were closely packed together and lacked serrations.
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This multi-layered wing arrangement might have helped strengthen the wing, considering that the primary and secondary feathers themselves were narrow and weak. The wing included three clawed fingers; however, unlike in some more primitive theropods, the longest two fingers were not separate, but were bound together by the skin and other tissue forming the wing, so Anchiornis was functionally two-fingered. These bound fingers were incorporated into a post-patagium, or flap of skin and other tissues that helped support the bases of the main wing feathers. Like the toes, the skin around the bottom of the fingers was covered in tiny, rounded scales.
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Reconstruction of Machimosaurus species; M. hugii was present alongside both Knoetschkesuchus species Besides K. langenbergensis, other crocodilians from the Langenberg Quarry include the marine Machimosaurus hugii and Steneosaurus aff. brevirostris, which would have lived offshore and fed on turtles and fish; and the amphibious generalist Goniopholis simus, which subsisted on a diet of both shelly and soft prey like modern alligators. The quarry is best known as the type locality of the brachiosaurid sauropod dinosaur Europasaurus holgeri, which was an insular dwarf. Isolated teeth show that there were at least four different types of theropods present at the locality, including the megalosaurid Torvosaurus sp.
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Further remains (including a premaxilla and lower jawbone) had been discovered as early as 1972, but were not described until 2017 by Cristiano Dal Sasso and colleagues. These remains allowed them to confidently assign Razanandrongobe as the oldest-known member of the Notosuchia, a group of crocodylomorphs, which partially filled a gap of 74 million years in the group's evolutionary history. Razanandrongobe shows a number of adaptations to a diet containing bones and tendons, including teeth with large serrations and bony structures reinforcing its palate and teeth. Measuring long, it was the largest member of the Notosuchia and may have occupied a predatory ecological niche similar to theropods.
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