Some were found to belong to long-necked, plant-eating sauropods, others to two-legged ornithopods.
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The researchers found the five jaws, ranging from young to mature, in the same area as other small ornithopods.
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The dinosaur would have been a small yet quick member of the large family called ornithopods, which also included iguanodons.
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The dinosaur Galleonosaurus dorisae would have been a small yet quick member of the large family called ornithopods, which also included iguanodons.
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In addition to the stegosaur footprints, they also spied what looked like tracks belonging to large ornithopods, which are like duck-billed dinosaurs.
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Bigger three-toed footprints with blunter toes may have been left by large-bodied two-legged plant-eaters called ornithopods or perhaps by a large theropod.
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Salinger's team also identified four types of tracks from two-legged, plant-eating ornithopods and six types of tracks from dinosaurs bedecked with spikes and plates, such as the stegosaurus.
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Herne said Diluvicursor, a member of a dinosaur group called ornithopods, was similar to another small, two-legged herbivorous dinosaur called Leaellynasaura that lived at about the same time and whose remains were unearthed about 9 miles (15 km) away.
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The ornithischians divided into armoured thyreophorans and unarmoured ornithopods and marginocephalians.
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Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.
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An artist's interpretation of Gideonmantellia, sometimes considered one of the most primitive ornithopods Restoration of Muttaburrasaurus, an early iguanodont Skeleton of Dysalotosaurus, a dryosaurid ornithopod from the Jurassic Life restoration of Iguanacolossus, an early styracosternan Reconstruction of Mantellisaurus, a primitive member of the Hadrosauriformes Mounted skeleton of Edmontosaurus, a saurolophine hadrosaur, and one of the last ornithopods Historically, most indeterminate ornithischian bipeds were lumped in as ornithopods. Most have since been reclassified.
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Prismatoolithidae is an oofamily of fossil eggs. They may have been laid by ornithopods or theropods.
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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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Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which preyed on sauropods, ornithopods, and ankylosaurs.
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The very largest-known ornithopods, like Shantungosaurus were as heavy as medium-sized sauropods at up to , and in length.
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The only known individual of Eousdryosaurus was a small dryosaurid, estimated at in length, comparable to immature individuals of Dryosaurus and Dysalotosaurus. The right femur measures long and the left shin bone (tibia) measures long. It is differentiated from other dryosaurids by various details of the vertebrae, hip, and hind limb. The foot is unique among ornithopods in that the first digit (the hallux or big toe) includes a single phalanx bone; most basal ornithopods had two phalanges, and most derived ornithopods, including hadrosaurs ("duckbills"), lost this digit.
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Norman, D.B., and Weishampel, D.B. (1990). Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). The Dinosauria.
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Other vertebrates include cladotherian mammals, a pipoid frog, and ceratodontiform fishes. Footprints indicate the presence of large ornithopods and pterosaurs as well.
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Folia:Buenos Aires, 1:112-255. [Spanish]Norman, D.B., and Weishampel, D.B. 1990. Iguanodontidae and related ornithopods. In: Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.).
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Trackways have also confirmed parental behavior among ornithopods from the Isle of Skye in northwestern Scotland.Dinosaur family tracks Footprints show maternal instinct after leaving the nest.
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Pu et al. 2013 noted that this dental morphology "likely maximized the biting stress during occlusion to cut fibers of plant material, similar to ornithopods and ceratopsians".
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This includes the ornithopods Trinisaura santamartaensis and Morrosaurus antarcticus, the nodosaurid Antarctopelta oliveroi, the shark Notidanodon sp. as well as some intermediate elasmosaurids, titanosaurs and a pterosaur.
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Iguanodontidae and related ornithopods. In D. B. Weishampel, H. Osmolska, and P. Dodson (eds.), The Dinosauria. University of California Press, Berkeley 510-533.D. B. Norman. 2004.
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Iguanodontidae and related ornithopods. In D. B. Weishampel, H. Osmolska, and P. Dodson (eds.), The Dinosauria. University of California Press, Berkeley 510-533.D. B. Norman. 2004.
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However, dinosaurs still dominated the state's terrestrial environments. Examples include ceratopsians, Bistahieversor, ornithopods, and sauropods. Some of these dinosaurs left behind an abundant trace fossil record. At the time the Dakota Formation was being deposited in northeastern New Mexico, more than 500 dinosaur tracks were imprinted in the sediments of Clayton Lake State Park. Another New Mexican Dakota exposure contains 55 parallel trackways left by ornithopods moving northward on all-fours.
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The humerus has reduced areas for muscle attachment, a featured shared with other South American ornithopods like Notohypsilophodon and Anabisetia. This and other similarities to South American ornithopods suggests that there may have been a distinct Southern Hemisphere ornithopod group, but at the time the authors cautioned that such an interpretation was not entirely justified. In 2015, the describers of Morrosaurus found that such a clade did indeed exist.
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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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As for herbivorous dinosaurs, the nodosaurid Animantarx was discovered in Carol's Site, near the type specimen of Eolambia. Teeth belonging to more basal ornithopods have also been discovered, with similar teeth having been referred to the Pachycephalosauria or to toothed birds by Cifelli in 1999. More complete remains referred to two different ornithopods – an orodromine and a basal iguanodont – remain unpublished. A giant oviraptorosaur has also been discovered, alongside teeth from ceratopsians and sauropods.
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The rebbachisaurid dinosaur Demandasaurus is known from the formation, alongside somphospondylan Europatitan as well as indeterminate small ornithopods, iguanodonts and spinosaurids, the earliest known stem- rhabdodontid (indeterminate) and the lizard Arcanosaurus.
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Macrogryphosaurus has been noted for its large size compared to other South American ornithopods. It has been estimated to have been around in length, though the only known individual may not have been fully grown. As such, it is the largest species of South American ornithopod outside of Hadrosauridae, and the largest species of elasmarian. Approaching the size of many more derived iguanodontian ornithopods, it is, compared to these derived taxa, much more graceful and lightly built in form.
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The discovery of the genus increases the anatomical knowledge of ornithopods and adds new data on the compositions of dinosaur faunas that lived in Patagonia close to Antarctica at the end of the Cretaceous.
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It is after Brown et al. (2013), the most recent analysis of hypsilophodonts. Ornithischia, Ornithopoda, and Iguanodontia were not designated in their result, and so are left out here. Additional ornithopods beyond Tenontosaurus are omitted.
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Microstructure of a thin slice from an isolated tooth Inferences regarding the method of feeding in Matheronodon can be made from the unique morphology of its teeth. The hadrosaurs, a contemporary successful group of ornithopods, had a large number of wide, high crowned teeth in tightly-packed rows. These were used in a complex method of chewing, a culmination of continued specialization throughout the evolution of iguanodonts. Rhabdodontids, which were more basal, had a far simpler arrangement, with teeth more similar to those of less specialized ornithopods.
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The dominant hypothesis over the last several decades has placed heterodontosaurids as basal ornithopods. However, others have suggested that heterodontosaurids instead share a common ancestor with Marginocephalia (ceratopsians and pachycephalosaurs), a hypothesis that has found support in some early 21st century studies. The clade containing heterodontosaurids and marginocephalians has been named Heterodontosauriformes. Heterodontosaurids have also been seen as basal to both ornithopods and marginocephalians. In 2007, a cladistic analysis suggested that heterodontosaurids are basal to all known ornithischians except Pisanosaurus, a result that echoes some of the very earliest work on the family.
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Gongbusaurus, by extrapolation from the remains of possible species "G." wucaiwanensis and other basal ornithopods, was a herbivorous bipedal animal around long. The tibia of "G." wucaiwanensis is 19.5 centimetres long. It would have been a strong runner.
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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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Norman, David B.; Sues, Hans-Dieter (2000). "Ornithopods from Kazakhstan, Mongolia and Siberia". In Benton, Michael J.; Shishkin, Mikhail A.; Unwin, David M.; Kurochkin, Evgenii N. The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. 462–479. .
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Ornithopods fall into distinct clades - Hypsilophodontidae, and Iguanodontia. Hypsilophodontids more closely resemble their ancestors than the heterodontosaurids do. The most distinctive features are short scapula and rod-shaped pre-pubic process. The earliest is Agilisaurus from the middle Jurassic of China.
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Changchunsaurus is based on the holotype JLUM L0403-j–Zn2, a skeleton and skull, with a premaxilla (upper beak) and partial lower jaw also known. Only the skull was figured and described in the official description. According to Zan et al. 2005, who described it, the animal shows a combination of features like those of derived ornithopods (reduction in size or loss of some skull fenestrae or holes), and features like those of more basal ornithopods (for example, five teeth in each premaxilla, short toothless portion of upper beak, and a small gap between beak teeth and cheek teeth).
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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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However, fossil trackways from the nearby Yangmeikeng area indicate an assemblage of predominantly ornithopods (hadrosaurids), but also nodosaurids, therizinosaurids, tyrannosaurids, oviraptorids, coelurosaurians, deinonychosaurians, the bird Wupus, sauropods (perhaps Gannansaurus), pterosaurs (Pteraichnus), and turtles (perhaps Jiangxichelys). The area was probably a lakeside environment.
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The known troodontids from this formation include Troodon, Pectinodon, and Paronychodon. A single species of coelurosaur is known from similar fossil formations includes Richardoestesia. left Ornithischians are abundant in the Hell Creek Formation. The main groups of ornithischians are ankylosaurians, ornithopods, ceratopsians, and pachycephalosaurians.
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The specific name honours Zhang Qian, the Chinese diplomat who reconnoitred the Silk Road in the second century B.C. It was regarded without comment as a dubious name in the most recent review of basal ornithopods, a not-uncommon fate for dinosaur names based on teeth.
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Ornithischians were more diverse than they were in the Jurassic Period. Tenontosaurus, Dakotadon, Protohadros, and Eolambia are some of the ornithopods that lived during this time period. Ankylosaurs replaced their stegosaur cousins in the Cretaceous. Ankylosaurs from the Early Cretaceous of North America include Sauropelta and Gastonia.
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Hand of Iguanodon, showing the distinctive thumb of the group About 157 million years ago, Ankylopollexia and Dryosauridae are believed to have split into separate evolutionary branches.Norman, David B.; Weishampel, David B. (1990). "Iguanodontidae and related ornithopods". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.).
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Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior, and hunting in packs, while others believe individuals may have been aggressive toward each other, and that congregations of this genus are the result of lone individuals feeding on the same carcasses.
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The authors tentatively it referred to Ornithopoda. The vertebra of a spinosaurid, NMV P221081, was also found at the site. In a 2013 review of ornithopods from Victoria, it was given a diagnosis and preliminary description.Rich T.H., Vickers-Rich P., Flannery T.F., Pickering D., Kool L., Tait A.M., Fitzgerald E.M.G. 2009.
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Shortly thereafter, a new revision appeared that showed that the characteristics listed as unusual for Arstanosaurus were really based on perspective, and that the maxilla was from an animal like Bactrosaurus, albeit indeterminate (a dubious name). The femur was uninformative.Norman, D.B., and Kurzanov, S.M. (1982). On Asian ornithopods (Dinosauria: Ornithischia). 2.
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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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Trackways of hundreds or even thousands of herbivores indicate that duck-bills (hadrosaurids) may have moved in great herds, like the American Bison or the African Springbok. Jack Horner's 1978 discovery of a Maiasaura ("good mother dinosaur") nesting ground in Montana demonstrated that parental care continued long after birth among the ornithopods.
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Later ornithopods became larger, but never rivalled the incredible size of the long-necked, long-tailed sauropods that they partially supplanted. The very largest, such as Shantungosaurus, were as heavy as medium-sized sauropods at up to 23 metric tons (25 short tons) but never grew much beyond 15 metres (50 feet).
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Many of the major groups of dinosaurs emerged during the Middle Jurassic, (including cetiosaurs, brachiosaurs, megalosaurs and primitive ornithopods). Descendants of the therapsids, the cynodonts, were still flourishing along with the dinosaurs. These included the tritylodonts and mammals. Mammals remained quite small, but were diverse and numerous in faunas from around the world.
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Martínez found no evidence that Notohypsilophodon was an iguanodont, and instead assigned it to the more basal Hypsilophodontidae, which made it at the time the only South American hypsilophodont. A hypsilophodontid assignment was supported by Rodolfo Coria in a 1999 review of South American ornithopods, but a more recent review of basal ornithopods found the fossil remains to be too fragmentary for classification beyond Euornithopoda, a clade within Ornithopoda including the "hypsilophodonts" and iguanodonts. Moreover, the Hypsilophodontidae are today considered to be a paraphyletic group, not consisting of directly related species forming a separate branch, but representing a series of successive branches splitting off the main euornithopod tree. A recent redescription of Notohypsilophodon found it to be basal in Ornithopoda, more primitive than Gasparinisaura.
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Cedrorestes is based on DMNH 47994, a partial skeleton including rib fragments, a sacrum, the left ilium and a portion of the right, a right thighbone, the right third metatarsal, and fragments of ossified tendons. These remains were in 2001 recovered from near the top of the Yellow Cat Member of the Cedar Mountain Formation, in east-central Utah. They were found scattered in a calcareous mudstone, and showed evidence of pre-burial damage, from weathering or trampling. This genus can be told apart from other iguanodontian ornithopods by its combination of a tall ilium, as is present in Iguanodon-like ornithopods, with a large lateral bony process above and behind the acetabulum and joint surface for the ischium, as is seen in hadrosaurids.
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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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Fewer teeth were present in the jaw, but they were taller, thinner, and individually larger. In life, they would have functioned like a pair of scissors in powerful but simple slicing bites. The microstructure of the teeth in Mantheronodon was also adapted for this action. These differences would have led to different diets in the two groups of ornithopods.
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Two have been named: Gargoyleosaurus parkpinorum and Mymoorapelta maysi. Ornithopods, bipedal herbivores, came in several types. Small "hypsilophodonts" included Drinker nisti, Laosaurus celer, "L." gracilis, Nanosaurus agilis, Othnielia rex, and Othnielosaurus consors. Larger but similar-looking dryosaurids were represented by Dryosaurus altus and the camptosaurid Uteodon aphanoecetes, which is currently known only from Dinosaur National Monument.
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This site, the Mosquero Creek site, also preserves a series of ten or more parallel trackways left by even larger two-legged ornithopod moving in the opposite direction as the other ornithopods. These New Mexican tracks provide important evidence of social behavior in dinosaurs. Geologic upheaval during the early Cenozoic era formed the state's basin and range physiographic province.
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The cladogram below follows Coria et al., 2013 phylogenetic analysis. Trinisaura is found to be an ornithopod, however the inclusion of Thescelosaurus neglectus is necessary to determine whether it is a basal iguanodont. In 2015, it along with several other Patagonian and Antarctic ornithopods was found to be a part of the basal group of iguanodonts, Elasmaria.
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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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Anoplosaurus (meaning "unarmored or unarmed lizard") is an extinct genus of herbivorous nodosaurid dinosaur, from the late Albian-age Lower Cretaceous Cambridge Greensand of Cambridgeshire, England. It has in the past been classified with either the armored dinosaurs or the ornithopods, but current thought has been in agreement with the "armored dinosaur" interpretation, placing it in the Ankylosauria.
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Hadrosauromorpha is a cohort of iguanodontian ornithopods, defined in 2014 by David B. Norman to divide Hadrosauroidea into the basal taxa with compressed manual bones and a pollex, and the derived taxa that lack them. The clade is defined as all the taxa closer to Edmontosaurus regalis than Probactrosaurus gobiensis. This results in different taxon inclusion depending on the analysis.
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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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Tyrannosauropus and were as such interpreted as belonging to a large theropod. However, Tyrannosauropus has since been declared a nomen dubium and the referred tracks likely belonged to hadrosaurid ornithopods. Similarly, the large Lark Quarry footprints are also now suggested to belong to an ornithopod, and are most similar to Amblydactylus gethingi, with the suggested referral of Amblydactylus cf. gethingi.
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Life restoration of Gideonmantellia, a candidate for a parent of Guegoolithus. Guegoolithus is classified as a spheroolithid, which would indicate it was laid by an ornithopod dinosaur. It is very similar to the eggs of Maiasaura peeblesorum and other hadrosaurs, but these were not common in Europe during the Early Cretaceous. G. turolensis is most likely laid by a closely related ornithopods.
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The Münchehagen dinosaur tracksite is a dinosaur track site in Germany. In 1999, Lockley and Wright discovered front prints left by large ornithopods walking along on all fours at the site. These rare traces were preserved in a single horizon of the Buckeburg Formation. Overall, Lockley and Wright documented twenty of slabs of ornithopod track-bearing rock, four of which recorded foreprints.
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Its climate was sub-tropical, similar to the present Mediterranean region. Since the Smokejacks Pit consists of different stratigraphic levels, fossil taxa found there are not necessarily contemporaneous. Dinosaurs from the locality include the ornithopods Mantellisaurus, Iguanodon, and small sauropods. Other vertebrates from the Weald Clay include crocodiles, pterosaurs, lizards (such as Dorsetisaurus), amphibians, sharks (such as Hybodus), and bony fishes (including Scheenstia).
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Fossil gastroliths have been found associated with both ornithopods and sauropods, though whether they actually functioned as a gastric mill in the latter is disputed. Salt water crocodiles also use gastroliths as ballast, stabilizing them in the water or helping them to dive. A dual function as both stabilizing ballast and digestion aid has been suggested for gastroliths found in plesiosaurs.
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A distinguishing postcranial feature of Genasauria is a pubic peduncle of the ilium that is less robust than the ischial peduncle. Genasauria is commonly divided into Neornithischia and Thyreophora. Neornithischia is characterized by asymmetrical distributions of enamel covering the crowns of the cheek teeth, an open acetabulum, and a laterally protruding ischial peduncle of the ilium. Neornithischia includes ornithopods, pachycephalosaurs, and ceratopsians.
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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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Sauropods are less common, with only an intermediate diplodocid as well as Dinheirosaurus; the camarasaurid Lourinhasaurus alenquerensis; the turiasaur Zby atlanticus; and the brachiosaurid Lusotitan known. Ornithischians are well represented, with identified remains persisting to Trimucrodon cuneatus; Alocodon kuehnei; the stegosaurians Dacentrurus armatus, Miragaia longicollum, and Stegosaurus ungulatus; the ankylosaurid Dracopelta zbyszewskii; the ornithopods Draconyx loureiroi, Camptosaurus sp., Phyllodon henkelli, and cf. Dryosaurus sp.
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The Wessex Formation possessed a wide array of fauna, including many other dinosaurs such as the carcharodontosaurian Neovenator, the compsognathid Aristosuchus; the medium size spinosauridae Baryonx; the basal neornithischian Hypsilophodon; the ornithopods Iguanodon, Mantellisaurus, and Valdosaurus; the sauropods Ornithopsis, Eucamerotus, and Iuticosaurus; and the ankylosaur Polacanthus. There were many contemporary mammal species which Eotyrannus likely fed on, including the spalacotheriid Yaverlestes and the eobaatarid Eobaatar.
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42 In this vein, David Lambert (1993) speculated that Ornitholestes, if it was a pack hunter, might have been able to "take on ornithopods as big as a half-grown Camptosaurus."Lambert (1993), p. 78 In 2007, John Foster, a specialist on the Morrison Formation, suggested the possibility of niche partitioning between Ornitholestes and its contemporary Coelurus, which was within the same size range.Foster (2007), p.
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Since embryos are unknown in cairanoolithid eggs, the identity of their parent is uncertain. They have long been considered to be eggs of titanosaurs or ornithopods (like Rhabdodon). However, numerous characteristics distinguish Cairanoolithus from sauropod eggs (oofamilies Megaloolithidae and Faveoloolithidae), even though they bear superficial similarities in size and shape. Cairanoolithus's columnar eggshell units are quite unlike the fan-shaped ones seen in Megaloolithus, Faveoloolithus, or Fusioolithus.
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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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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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Conditions were likely to be at their coldest during the polar nights, which lasted up to three months. One interpretation of the fossil material is that small ornithopods had adaptations to survive cooler conditions. Bone growth of presumed related taxa shows they were active all year round, so they did not hibernate through the winter. The structure of these bones also suggests warm-bloodedness, which would help maintain its body heat.
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Pachycephalosaurus gives its name to the Pachycephalosauria, a clade of herbivorous ornithischian ("bird hipped") dinosaurs which lived during the Late Cretaceous Period in North America and Asia. Despite their bipedal stance, they were likely more closely related to the ceratopsians than the ornithopods. Pachycephalosaurus is the most famous member of the Pachycephalosauria (though not the best- preserved member). The clade also includes Stenopelix, Wannanosaurus, Goyocephale, Stegoceras, Homalocephale, Tylocephale, Sphaerotholus and Prenocephale.
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Tyrannosaur- inflicted damage has been found on skeletons of hadrosaurs and Triceratops that seemed to have survived initial attacks. Some researchers argue that if Tyrannosaurus were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. The top prey were the larger marginocephalians and ornithopods. The other tyrannosaurids share so many characteristics with Tyrannosaurus that only small dromaeosaurs remain as feasible top predators.
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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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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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Ornithopods are common in the Hell Creek Formation, and are known from several species of the ornithopod Thescelosaurus and the hadrosaurids Edmontosaurus, and a possible species of Parasaurolophus. Several pachycephalosaurians have been found in the Hell Creek Formation and in similar formations. Among them are the derived pachycephalosaurids Stygimoloch, Dracorex, Pachycephalosaurus, Sphaerotholus, and an undescribed specimen from North Dakota. The first two might be junior synonyms of Pachycephalosaurus.
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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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Wightia inhabited the area presented by southern England's Wessex Formation, at the time a floodplain. The formation contains an abundance of insects like Dungeyella. Herbivores ranged from small mammals like Eobaatar, Loxaulax and Yaverlestes to ornithopods, themselves ranging from the small Hypsilophodon to large iguanodonts like Mantellisaurus. The largest predators of the area and time were the spinosaurid Baryonyx and the allosauroid Neovenator, as well as the basal tyrannosaur Eotyrannus.
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Through cladistic analysis, it was found to be more basal than Dryosaurus and Anabisetia, but more derived than Tenontosaurus and Gasparinisaura. More recently, the describers of Macrogryphosaurus found their genus and Talenkauen to be related, and coined the clade Elasmaria for the two genera. In 2015, several other Patagonian and Antarctic ornithopods were also found to be related. Cladogram based in the phylogenetic analysis of Rozadilla et al.
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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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In the appendicular regions, hadrosauromorphans the scapulae are not J shaped, instead having an overhanging projection. The lower forelimb bones are more slender in both hadrosauromorphans and Probactosaurus, unlike their more robust ancestors. Probactosaurus, however, possesses the basal condition of having a small, conical pollex, like in earlier ornithopods such as Iguanodon or Hypselospinus. This absence of a pollex is also linked to a reduction of the carpal bones, and a less mobile manus.
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Triceratops), armored dinosaurs (Thyreophora) such as stegosaurs and ankylosaurs, pachycephalosaurs and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds, often segregated by age group, with juveniles forming their own flocks separate from adults. Some were at least partially covered in filamentous (hair- or feather- like) pelts, and there is much debate over whether these filaments found in specimens of Tianyulong, Psittacosaurus, and Kulindadromeus may have been primitive feathers.
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As its forelimbs were roughly half the length of its hindlimbs, Altirhinus appears to have been primarily bipedal. However, its carpals (wrist bones) were thick and blocky, and the three middle fingers of its hand were wide, hyperextendable, and ended in hoof-like bones. This indicates that the forelimbs were also capable of supporting weight. Like many ornithopods, Altirhinus may have spent a significant amount of time in a quadrupedal position, perhaps while feeding.
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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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Triceratops and other animals of the Hell Creek Formation Ornithischians are abundant in the Scollard Lance, Laramie, Lance, Denver, and Hell Creek Formation. The main groups of ornithischians are ankylosaurians, ornithopods, ceratopsians, and pachycephalosaurians. Three ankylosaurians are known, Ankylosaurus, Denversaurus, and possibly a species of Edmontonia or an undescribed genus. Multiple genera of ceratopsians are known from the formation other than Triceratops, the leptoceratopsid Leptoceratops, and the chasmosaurine ceratopsids Torosaurus, Nedoceratops and Tatankaceratops.
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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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Aside from the long narrow beak, the skull also had teeth in the premaxilla, or upper beak (a primitive trait among ornithopods). Long rod- like bones called palpebrals were present over the eyes, giving the animal heavy bony eyebrows. Its teeth were of two types: small pointed premaxillary teeth, and leaf-shaped cheek teeth. Six small teeth were present in both premaxillae, with a toothless section at the tip of the beak.
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Parksosaurus (meaning "William Parks's lizard") is a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur. It is one of the few described non- hadrosaurid ornithopods from the end of the Cretaceous in North America, existing around 70 million years ago.
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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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Chewing is largely an adaptation for mammalian herbivory. Carnivores generally chew very little or swallow their food whole or in chunks. This act of gulping food (or medicine pills) without chewing has inspired the English idiom "wolfing it down". Ornithopods, a group of dinosaurs including the Hadrosaurids ("duck-bills"), developed teeth analogous to mammalian molars and incisors during the Cretaceous period; this advanced, cow-like dentition allowed the creatures to obtain more nutrients from the tough plant life.
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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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The Entrada Sandstone also preserves many footprints of mid-to-large sized carnivorous dinosaurs across more than thirty tracksites in the eastern part of the state. These tracksites form "a single vast expanse of tracks covering an area of over 300 square miles", or roughly 1,000 square kilometers. This is known as the Moab megatracksite. During the Late Jurassic a group of small to mid-sized ornithopods left behind another significant series of trackways that have since fossilized.
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Other herbivorous groups like ornithomimids, therizinosaurs, pachycephalosaurs, small ornithopods, nodosaurids and ankylosaurids were also represented. Small predatory dinosaurs like oviraptorosaurs, troodonts and dromaeosaurs hunted smaller prey than the huge tyrannosaurids; Daspletosaurus and Gorgosaurus, which were two orders of magnitude larger in mass. Intervening predatory niches may have been filled by young tyrannosaurids. A Saurornitholestes dentary has been discovered in the Dinosaur Park Formation that bore tooth marks left by the bite of a young tyrannosaur, possibly Gorgosaurus.
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Life reconstruction of Y. downsi Yinlong was a relatively small dinosaur, with a total length of about from nose to tail, and a weight of about . Long robust hindlimbs and shorter slender forelimbs with three-fingered hands suggests a bipedal lifestyle like many small ornithopods. Despite a virtually frill-less and totally hornless skull, Yinlong is a ceratopsian. Its skull is deep and wide and relatively large compared to most ornithischians, but also proportionately smaller than most other ceratopsians.
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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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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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The Snow Hill Island Formation is a Late Campanian geologic formation found on James Ross Island, James Ross Island group, Antarctica. Remains of a paravian theropod Imperobator antarcticusEly & Case, 2019 have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis and Morrosaurus antarcticus, the nodosaurid Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids,O'Gorman, 2012, p.2 lithostrotian titanosaurs and an indeterminate pterosaur.
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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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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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Lambeosaurini, previously known as Corythosaurini, is one of four tribes of hadrosaurid ornithopods from the family Lambeosaurinae. It is defined as all lambeosaurines closer to Lambeosaurus lambei than to Parasaurolophus walkeri, Tsintaosaurus spinorhinus, or Aralosaurus tuberiferus, which define the other three tribes. Members of this tribe possess a distinctive protruding cranial crest. Lambeosaurins walked the earth for a period of around 12 million years in the Late Cretaceous, though they were confined to regions of modern-day North America and Asia.
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The jugal below and behind the orbit bears the same shape as in hadrosaurids, with a high rear process, and articulated with the quadratojugal and quadrate that are also very similar to more derived taxa. As in other ornithopods, the is a tri- radiate bone surrounding sides of the orbit, and . Contact between the postorbital and the excludes the flattened and wide from the supratemporal fenestra. In Ouranosaurus and related taxa the are small, and articulates with the broadened and textured lacrimal.
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The Twin Mountains Formation, also known as the Twin Mountain Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age (Lower Cretaceous), and is notable for its dinosaur fossils. Dinosaurs from this formation include the large theropod Acrocanthosaurus, the sauropod Sauroposeidon, as well as the ornithopods Tenontosaurus and Convolosaurus. It is the lowermost unit of the lower Cretaceous, lying unconformably on Carboniferous strata.
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Various specimens of Dysalotosaurus are known, all representing animals that were not yet sexually mature at the time of their deaths. Ontogenetic studies demonstrate typical aging trends, such as a lengthening of the snout and relative shrinking of the orbit. Differences in dentition as the animals aged also suggest a change from an omnivorous diet early in life to fully herbivorous feeding habits as an adult. This switch reflects the general evolutionary trend towards obligate herbivory among iguanodontians and other ornithopods.
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The potential co-evolution of plants and herbivorous dinosaurs has been subject to extensive speculation. The appearance of prosauropods in the late Triassic has been tentatively linked either to the demise or diversification of types of flora at that time. The rise of ceratopsids and iguanodont and hadrosaurid ornithopods in the Cretaceous has been tentatively linked to the angiosperm radiation. Unfortunately, there are still no hard data on dietary preferences of herbivorous dinosaurs, apart from data on chewing technique and gastroliths.
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Also, its subdued ornamentation contrasts strongly with the heavily sculpted eggshells of sauropod eggs, and it has a different pore system. Eggs of ornithopods (Spheroolithidae and Ovaloolithidae), on the other hand, show much closer similarity to cairanoolithids in ornamentation and pore system. However, ornithopod eggs are typically much smaller, and the crystal structure of their eggshell units is distinct. Restorations of Struthiosaurus, the possible parent of Cairanoolithus The cladistic analysis by Sellés and Galobart in 2015 supported an ornithischian parentage.
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Lesothosaurus diagnosticus reconstruction Lesothosaurus was originally considered an ornithopod. However, more recent work by Paul Sereno has suggested that it may actually represent one of the most primitive of all known ornithischian dinosaurs. The taxonomic history of Lesothosaurus is complex and it has long been confused with Fabrosaurus, another small ornithischian from the same locality. In 2005, Richard J. Butler published a new phylogenetic study of ornithischians, in which he proposed that Lesothosaurus was a basal member of the clade Neornithischia, which includes pachycephalosaurs, ceratopsians and ornithopods.
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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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Ouranosaurus bears more similarities to other derived iguanodonts than more basal ornithopods. Remodeling is present in the subadult paratype, and high vascular density and circumferential arrangement of the microstructure suggests fast growth. Faster growth occurs in the same phylogenetic groups as higher body size, although their relationship is unclear. Ouranosaurus is a similar size to more basal Tenontosaurus which has slow growth, so either faster growth is caused by body size or Tenontosaurus is the maximum size of an ornithopod with a slow growth rate.
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Hadrosaurids (, hadrós, "stout, thick"), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck- billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The family, which includes ornithopods such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period in what is now Asia, Europe, Antarctica, South America, and North America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout.
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Ankylopollexia is an extinct clade of ornithischian dinosaurs that lived from the Late Jurassic to the Late Cretaceous. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna. The name stems from the Greek word, “ankylos”, mistakenly taken to mean stiff, fused (in fact the adjective means bent or curved; used of fingers, it can mean hooked), and the Latin word, “pollex”, meaning thumb. Originally described in 1986 by Sereno, this most likely synapomorphic feature of a conical thumb spine defines the clade.
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Ossified tendons are present on all the vertebrae, except for those in the cervical region. On no vertebrae do the tendons extend below the transverse processes. Each tendon is flattened at its origin, and transversely ovoid in the central rod, ending at a rounded point. Aside from those found on Corythosaurus casuarius, extensive skin impressions have been found on Edmontosaurus annectens and notable integument has also been found on Brachylophosaurus canadensis, Gryposaurus notabilis, Parasaurolophus walkeri, Lambeosaurus magnicristatus, L. lambei, Saurolophus angustirsotris and on unidentified ornithopods.
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The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. It is also known as the adlacrimal or supraorbital, although the latter term may not be confused with the supraorbital in osteichthyan fishes. In ornithischians, the palpebral can form a prong that projects from the front upper corner of the orbit. It is large in heterodontosaurids, basal ornithopods such as Thescelosaurus (as Bugenasaura) and Dryosaurus, and basal ceratopsians such as Archaeoceratops;You Hailu and Dodson, Peter. (2004).
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The Glen Rose Formation represents a coastal environment, with possible Acrocanthosaurus tracks preserved in mudflats along the ancient shoreline. As Acrocanthosaurus was a large predator, it is expected that it had an extensive home range and lived in many different environments in the area. Potential prey animals include sauropods like Astrodon [published online] or possibly even the enormous Sauroposeidon, as well as large ornithopods like Tenontosaurus. The smaller theropod Deinonychus also prowled the area but at in length, most likely provided only minimal competition, or even food, for Acrocanthosaurus.
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Styracosterns (a clade of ornithopods that includes hadrosaurs and their close relatives) are, like G. turolensis, incredibly common in the lower Cretaceous of Spain. Given that fossils of Guegoolithus span a larger time period than is likely for a single species, the fossils probably represent many different styracostern species with structurally indistinguishable eggshells. Because Guegoolithus remained unchanged for upwards of 5 million years and it is very similar to the late Cretaceous spheroolithids, Moreno-Azanza et al. (2017) concluded that the nesting behavior of hadrosaurs and their close relatives remained unchanged for 80 million years.
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Geological evidence suggests that Deinonychus inhabited a floodplain or swamplike habitat. The paleoenvironment of both the upper Cloverly Formation and the Antlers Formation, in which remains of Deinonychus have been found, consisted of tropical or sub-tropical forests, deltas and lagoons, not unlike today's Louisiana. Other animals Deinonychus shared its world with include herbivorous dinosaurs such as the armored Sauropelta and the ornithopods Zephyrosaurus and Tenontosaurus. In Oklahoma, the ecosystem of Deinonychus also included the large theropod Acrocanthosaurus, the huge sauropod Sauroposeidon, the crocodilians Goniopholis and Paluxysuchus, and the gar Lepisosteus.
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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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Lungfish, triconodont mammals, and several species of turtles lived in the Cloverly, while crocodilians prowled the rivers, lakes, and swamps, providing evidence of a year-round warm climate. The Late Jurassic fauna dominated by allosauroids, stegosaurs, and many varieties of huge sauropods gave way by Cloverly times to an Early Cretaceous fauna in which dromaeosaurs, ornithopods, and nodosaurs like Sauropelta were predominant. After the Cloverly ended, a large wave of Asian animals, including tyrannosaurids, ceratopsians, and ankylosaurids would disperse into western North America, forming the mixed fauna seen throughout the Late Cretaceous.
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This dinosaur is thought to be closely related to another Patagonian ornithopod, Gasparinisaura, although the lack of skull material makes it difficult to place with precision. When originally described, Gasparinisaura and Anabisetia were thought to be basal iguanodontians, more derived than Tenontosaurus and members of the clade Euiguanodontia, and seen as endemic remnants of an early dispersion of basal iguanodontians on Pangea. Relatively recent cladistic analyses performed by Coria and others indicated that Gasparinisaura lies just outside of Iguanodontia, closer to North American ornithopods like Thescelosaurus and Parksosaurus.Norman, D.B., Sues, H-D.
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Like the humerus, the femur is bowed, but outwards. However, characteristically, the bottom half of the femur is straight. The fourth trochanter, located halfway down the femur, is vertically tall and triangular, similar to Probactrosaurus, Gongpoquansaurus, and other iguanodonts but dissimilar to more basal ornithopods. Like the ulna and radius, the tibia and fibula have straight shafts, and they articulate with each other; a roughened projection on the bottom of the fibula fits between two bulb-like condyles located just behind the cnemial crest on the bottom end of the tibia.
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Later researchers, such as Michael Benton, have ranked it as an infraorder of a suborder Cerapoda, which unites the ceratopsians and ornithopods. In 2006, Robert Sullivan published a re-evaluation of pachycephalosaur taxonomy. Sullivan considered attempts by Maryańska and Osmólska to restrict the definition of Pachycephalosauria redundant with their Pachycephalosauridae, since they were diagnosed by the same anatomical characters. Sullivan also rejected attempts by , in his phylogenetic studies, to re-define Pachycephalosauridae to include only "dome- skulled" species (including Stegoceras and Pachycephalosaurus), while leaving more "basal" species outside that family in Pachycephalosauria.
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In 1984, David B. Weishampel proposed a new hypothesis on how hadrosaurids fed. His study of the sutures between bones in fossil skulls concluded that ornithopods, a group of bird-hipped dinosaurs that includes hadrosaurids, had flexible upper jaws and that when the lower jaw clamped shut, pressure would spread outward from both sides of the upper jaw. The upper teeth would grind against the lower teeth like rasps, trapping the plants and grinding them up. The theory remained largely unproven until the study by Purnell, Williams and Barrett, which Science magazine called, "The strongest independent evidence yet for this unique jaw motion".
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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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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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Studies suggest that the paleoenvironment of the Two Medicine Formation featured a seasonal, semi-arid climate with possible rainshadows from the Cordilleran highlands. Lithologies, invertebrate faunas, and plant and pollen data suggest that during the Campanian, this region experienced a long dry season and warm temperatures. The extensive red beds and caliche horizons of the upper Two Medicine are evidence of at least seasonally arid conditions. The Two Medicine Formation has produced the remains of oviraptorosaurs, ornithopods, the nodosaur Edmontonia, the ceratopsians Achelousaurus, Brachyceratops, Cerasinops, and Einiosaurus among others, Troodon, the dromaeosaurids Bambiraptor, Dromaeosaurus and Saurornitholestes, and the tyrannosauroids Albertosaurus, Daspletosaurus and Gorgosaurus.
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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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Three-toed feet of Iguanodon Ornithopoda means "bird feet", from the Greek ornithos ("bird") and pous ("feet"); this refers to their characteristic three-toed feet, although many early forms retained four toes. They were also characterized by having no armour, the development of a horny beak, an elongated pubis that eventually extended past the ilium, and a missing hole in the lower jaw, called a Mandibular fenestrae. A variety of ornithopods and related cerapods had thin cartilaginous plates along the outside of the ribs; in some cases, these plates mineralized and were fossilized. The function of these intercostal plates is unknown.
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Work in the early 2000s has challenged the Weishampel model. A study published in 2008 by Casey Holliday and Lawrence Witmer found that ornithopods like Edmontosaurus lacked the types of skull joints seen in those modern animals that are known to have kinetic skulls (skulls that permit motion between their constituent bones), such as squamates and birds. They proposed that joints that had been interpreted as permitting movement in dinosaur skulls were actually cartilaginous growth zones. An important piece of evidence for Weishampel's model is the orientation of scratches on the teeth, showing the direction of jaw action.
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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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By the 1980s, the affinities of the pachycephalosaurs within Ornithischia were unresolved. The main competing views were that the group was closest to either ornithopods or ceratopsians, the latter view due to similarities between the skeleton of Stegoceras and the "primitive" ceratopsian Protoceratops. In 1986, American palaeontologist Paul Sereno supported the relationship between pachycephalosaurs and ceratopsians, and united them in the group Marginocephalia, based on similar cranial features, such as the "shelf"-structure above the occiput. He conceded that the evidence for this grouping was not overwhelming, but the validity of the group was supported by Sues and Galton in 1987.
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When it was described in 1962, Heterodontosaurus was classified as a primitive member of Ornithischia, one of the two main orders of Dinosauria (the other being Saurischia). The authors found it most similar to the poorly known genera Geranosaurus and Lycorhinus, the second of which had been considered a therapsid stem-mammal until then due to its dentition. They noted some similarities with ornithopods, and provisionally placed the new genus in that group. The palaeontologists Alfred Romer and Oskar Kuhn independently named the family Heterodontosauridae in 1966 as a family of ornithischian dinosaurs including Heterodontosaurus and Lycorhinus.
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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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Calvo et al. (2007) coined Elasmaria to accommodate Macrogryphosaurus and Talenkauen, which they recovered as basal iguanodonts distinct from other iguanodontians in having mineralized plates on the ribs. In 2016, a paper describing the genus Morrosaurus found Elasmaria to be far larger than its initial contents of two taxa, instead containing a variety of ornithopods from the Southern Hemisphere. In 2019, Matthew C. Herne and colleagues redefined Elasmaria as "all taxa closer to Macrogryphosaurus gondwanicus and Talenkauen santacrucensis than to Hypsilophodon foxii or Iguanodon bernissartensis", expanding the definition to include the large number of taxa now found to be part of the clade.
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Thyreophorans exhibits depict their defensive anatomical features against predators in the form of bone shields, spikes, tail clubs and so forth. Camarasaurus, a large- sized sauropod dinosaur, found in central and western United States are exhibited in their original curved form. The exposition part dedicated to ornithopods is centred on the morphological characteristics most related to their vegetarian diet namely toothless snout, tooth batteries, mobile skull bones, and development of jowls and presence of hoofs on their feet. The space dedicated to thyreophorans shows the main defensive elements of this group of dinosaurs against predators such as bone shields, spikes, tail clubs and so forth.
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Restoration of Tarbosaurus pursuing S. angustirostris S. osborni is known only from the upper part (unit 4) of the Horseshoe Canyon Formation. It lived alongside other dinosaur species including the ornithopods Hypacrosaurus altispinus and Parksosaurus warreni, ankylosaurid Anodontosaurus lambei, pachycephalosaurid Sphaerotholus edmontonense, ornithomimids Ornithomimus brevitertius and an unnamed species of Struthiomimus, small theropods including Atrociraptor marshalli and Albertonykus borealis, and the tyrannosauroid Albertosaurus sarcophagus. The dinosaurs from this formation form part of the Edmontonian land vertebrate age. The Horseshoe Canyon Formation is interpreted as having a significant marine influence, due to an encroaching Western Interior Seaway, the shallow sea that covered the midsection of North America through much of the Cretaceous.
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The vegetation of the Wessex Formation was savannah- or chaparral-like, and included Caytoniales, cycads, ginkgos, conifers, and angiosperms. Other pterosaurs from the Wessex Formation include Caulkicephalus, "Ornithocheirus nobilis" (which is considered a dubious species), an undetermined ctenochasmatine, an azhdarchoid, and one or two other undetermined istiodactylids. This diversity is comparable to that seen in other parts of the world during the Early Cretaceous, and the lack of toothless pterosaurs may be due to preservation bias. Dinosaurs from the Wessex Formation include the theropods Ornithodesmus, Neovenator, Aristosuchus, Thecocoelurus, and Calamospondylus; the ornithopods Iguanodon, Hypsilophodon, and Valdosaurus; the sauropods Pelorosaurus and Chondrosteosaurus; and the ankylosaur Polacanthus.
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Indeterminate bones from small ornithopods, as well as part of the tail of a large ornithopod, were mixed in with the remains of Mierasaurus as well. A large allosauroid theropod is represented by teeth, and a new species of polacanthine ankylosaurian has also been found. Non-dinosaurs are represented by skull fragments and teeth from possibly goniopholididae crocodyliforms, as well as shell fragments of a turtle similar to Naomichelys. The area was a waterlogged bog-like environment, judging by the plastic deformation of the bones, the presence of horizontal root systems, and the better-preserved condition of the top surfaces of the bones (which suggests that invertebrates grazed on the bottom surfaces).
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Like ornithopods, Omphalosaurus have a high rate of tooth replacement and smooth secondary occlusal surfaces, but the lack of fibrous marine plants during the Middle Triassic make it unlikely that it was herbivorous. Ammonites and pseudoplanctonic halobiid bivalves were, on the contrary, common in Omphalosaurus’ range and time period, and their shells were hard but thin. Sander and Faber hypothesized that Omphalosaurus could have had fleshy cheeks and used suction feeding to make up for the lack of grasping dentition, and could then proceed to grind through the shells, allowing them to feed on these animals. Recent evidence suggests that they focused their hunting on ammonites over bivalves, the latter of which is preferred by placodonts.
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Ossified tendons from the tail of UALVP 2 Gilmore's classification was supported by the American palaeontologists Barnum Brown and Erich Maren Schlaikjer in their 1943 review of the dome-headed dinosaurs, by then known from 46 skulls. From these specimens, Brown and Schlaikjer named the new species T. sternbergi and T. edmontonensis (both from Alberta), as well as moving the large species T. wyomingensis (which was named in 1931) to the new genus Pachycephalosaurus, along with two other species. They found T. validus distinct from T. formosus, but considered S. brevis the female form of T. validus, and therefore a junior synonym. By this time, the dome-headed dinosaurs were either considered relatives of ornithopods or of ankylosaurs.
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Front of reconstructed skeleton, Rocky Mountain Dinosaur Resource Center Thescelosaurus has generally been allied to Hypsilophodon and other small ornithopods as a hypsilophodontid, although recognized as being distinct among them for its robust build, unusual hindlimbs, and, more recently, its unusually long skull. Peter Galton in 1974 presented one twist to the classic arrangement, suggesting that because of its hindlimb structure and heavy build (not cursorial, or built for running, by his definition), it should be included in the Iguanodontidae. This has not been followed, with Morris arguing strongly against Galton's classification scheme. At any rate, Galton's Iguanodontidae was polyphyletic and not a natural group, and so would not be recognized under modern cladistic usage.
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"Biscoveosaurus" is the informal name of an ornithopod dinosaur specimen from the Early Maastrichtian age Snow Hill Island Formation of James Ross Island, Antarctica. It comes from the Cape Lamb Member of the formation, the same member as Morrosaurus, another basal ornithopod. As such, it's been suggested it may be a secondary specimen of that species, but as the holotype of Morrosaurus is fragmentary and doesn't overlap with the material of "Biscoveosaurus", this can't as yet be tested. The specimen consists of dentaries, teeth, a braincase, parts of the maxillae, forelimb elements, assorted vertebrae, and the pectoral girdle; this makes it unique compared to the other James Ross Island ornithopods, which don't presever both cranial and postcranial remains.
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From the Cenomanian to the Maastrichtian, Appalachia was inhabited by various groups of dinosaurs including, hadrosauroids, hadrosaurs, nodosaurs, leptoceratopsians, indeterminate ornithopods, tyrannosauroids, dromaeosaurs, ornithomimids, and indeterminate maniraptors lived in the area. There is also fossil evidence of possible chasmosaurs, lambeosaurs, sauropods, allosaurs, caenagnathids, and troodontids that might have inhabited the area. In Late Cretaceous North America, the dominant predators were the tyrannosaurs, huge predatory theropods with proportionately massive heads built for ripping flesh from their prey. Tyrannosaurs were the dominant predators in Appalachia too, but rather than the massive Tyrannosauridae, like Gorgosaurus, Albertosaurus and Lythronax, which evolved around the same time that the Western Interior Seaway had fully separated Laramida from Appalachia, the smaller dryptosaurs were the top predators of Appalachia.
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In those two groups, the forelimbs of quadrupedal species were usually rotated so that the hands faced forward with palms backward ("pronated") as the animals walked. Triceratops, like other ceratopsians and the related quadrupedal ornithopods, together forming the Cerapoda, walked with most of their fingers pointing out and away from the body, the original condition for dinosaurs, also retained by bipedal forms like the theropods. In Triceratops, the weight of the body was carried by only the first three fingers of the hand, while digits 4 and 5 were vestigial and lacked claws or hooves. The phalangeal formula of the hand is 2-3-4-3-1, meaning that the first or innermost finger of the forelimb has two bones, the next has three, etc.
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Restoration of Dineobellator in its ecosystem Dineobellator is part of the Ojo Alamo Formation fauna in southern Laramidia, at time a lush floodplain dominated by wetlands and riparian gymnosperm forests. It lived among alongside large dinosaurs like ceratopsians (Ojoceratops and Torosaurus), hadrosaurs (Edmontosaurus and Kritosaurus), two types of ankylosaur (including nodosaurid Glyptodontopelta), and the titanosaur Alamosaurus; smaller herbivorous and omnivorous dinosaurs in the ecosystem as of yet not known from any remains likely included thescelosaurine ornithopods like Thescelosaurus and pachycephalosaurs like Pachycephalosaurus. The top predators of the formation's ecosystem were the azhdarchid pterosaur Quetzalcoatlus and Tyrannosaurus. The presence of a dromaeosaur suggests that the dromaeosaurs were active predators that had discrete ecological niches even in the presence of large tyrannosaurs.
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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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Skeleton of Thescelosaurus edmontonensis in display as preserved The first expansive analysis on the relationships of Hypsilophodontidae was that of Swinton in 1936, during a redescription of Hypsilophodon from new specimens. The possible hypsilophodonts Geranosaurus and Stenopelix were removed from the clade (then the subfamily Hypsilophodontinae), and considered to be intermediate basal ornithopods, as there were no features linking them to Hypsilophodon. Thescelosaurus was considered within the family, because of the large number of shared features, as well as Dysalotosaurus, from the Kimmeridgian of Tanzania. Laosaurus and Dryosaurus were not considered hypsilophodonts because of their lack of distinguishable features, as Swinton concluded that they were probably in the family Laosauridae, intermediate between Hypsilophodontidae and Iguanodontidae, and were probably synonyms of each other as well.
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It is also possible that the recovered dinosaurs were not from the landmass itself, but from the rocky islands of the adjacent archipelago in the Kristianstad Basin itself. Dinosaur fossils recovered from the Kristianstad Basin can be confidently attributed to theropod, ornithopod and leptoceratopsid dinosaurs. The recovered dinosaurs all represent animals with lengths less than three meters (9 ft), but this does not necessarily mean that larger dinosaurs were absent; it is equally likely that only small animals were transported out into the sea where they could be fossilized and preserved. When large dinosaurs are excluded, the dinosaur fauna preserved in the Kristianstad Basin resembles that of Campanian–Maastrichtian dinosaur- bearing formations in Canada, which also include small ornithopods (such as Parksosaurus) and leptoceratopsids (such as Unescoceratops).
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Ornithopods () or members of the clade Ornithopoda ( or ) are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow. They reached their apex of diversity and ecological dominance in the hadrosaurids (colloquially known as 'duck-bills'), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known from all seven continents, though they are generally rare in the Southern Hemisphere.
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However, muscle scars or other indications of attachment have not been found for the plates, which argues against a respiratory function. Recent histological study of layered plates from a probable subadult indicates that they may have started as cartilage and became bone as the animal aged. Such plates are known from several other ornithopods and their cerapodan relatives. The nature of this genus' integument, be it scales or something else, is currently unknown, although potential evidence exists: Charles Gilmore described patches of carbonized material near the shoulders as possible epidermis, with a "punctured" texture, but no regular pattern, and William J. Morris suggested that armor was present, in the form of small scutes he interpreted as located at least along the midline of the neck of one specimen.
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Skeleton of Laosaurus consors as drawn by Othniel Marsh (since named Othnielosaurus) Hypsilophodontidae was named originally in 1882 by Louis Dollo, as a family to include Hypsilophodon and other small ornithopods with a single row of teeth, four pedal digits, and a rhomboid sternum. For several decades after its naming the family only included Hypsilophodon. In 1911 Karl von Zittel published a textbook on vertebrate classifications, in which he included multiple genera in "Hypsilophontidae" (sic for Hypsilophodontidae), including Hypsilophodon, Nanosaurus, Laosaurus and Dryosaurus. Zittel considered the family to unite all taxa that lacked premaxilla teeth, had a single row of maxilla teeth, neck vertebrae which have flat articulations or a flat front and round back, fused sacral vertebrae, a femur shorter than the tibia, 5 fingered manus' and 4 toed peds.
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LACM 115747 (holotype), left maxilla Fruitadens is known from fossils recovered under a valid paleontological permit in the 1970s and 1980s by teams led by George Callison, for the Natural History Museum of Los Angeles County (LACM). The discovery area, on lands managed by the Bureau of Land Management, is known as the Fruita Paleontological Area; the specimens were found there in sandstones of the Brushy Basin Member. Roughly equivalent beds have been dated to 150.3 ± 0.3 million years old and 150.2 ± 0.5 million years old, indicating an early Tithonian age. The fossils now named Fruitadens were first thought to belong to a fabrosaurid similar to Echinodon, a genus from the Early Cretaceous of England; Fabrosauridae at the time was considered a general group of primitive ornithopods, and Echinodon itself had not yet been reclassified as a heterodontosaurid.
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Triceratops skeleton, Natural History Museum of Los Angeles County Under phylogenetic nomenclature, dinosaurs are usually defined as the group consisting of the most recent common ancestor (MRCA) of Triceratops and modern birds (Neornithes), and all its descendants. It has also been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (herbivorous quadrupeds with horns and frills), ornithopods (bipedal or quadrupedal herbivores including "duck-bills"), theropods (mostly bipedal carnivores and birds), and sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails). Birds are now recognized as being the sole surviving lineage of theropod dinosaurs.
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Morrosaurus was classified in the group Iguanodontia, as a basal member of Euiguanodontia. This in turn formed a clade with other ornithopods of Patagonia and Antarctica, particularly Trinisaura, Gasparinisaura, Anabisetia, Notohypsilophodon, Talenkauen and Macrogryphosaurus in a group called Elasmaria, whose members are distinguished by their adaptation to a running lifestyle which would be reflected by the narrow foot with a thin fourth metatarsal which indicates a high speed running; subsequently expanded chevrons, a feature that is associated with a greater surface area for attachment of the lateral muscles of the tail, which would give good control of the movements of this; and a curved humerus which demonstrates the absence of a deltopectoral ridge and therefore that the front leg was not used for walking. It cannot be determined, however, if Morrosaurus itself possessed these characteristics due to their limited remains. The existence of this clade may indicate that Patagonia, Antarctica and Australia shared the same type of fauna.
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Evans was also involved in the naming of the ornithopods Albertadromeus syntarsus Brown, Evans, Ryan, & Russell, 2013; Plesiohadros djadokhtaensis Tsogtbaatar, Weishampel, Evans, & Watabe, 2014; and Gobihadros mongoliensis Tsogtbaatar, Weishampel, Evans, & Watabe, 2019; the pachycephalosaurians Acrotholus audeti Evans, Schott, Larson, Brown, & Ryan, 2013; and Foraminacephale brevis Schott & Evans, 2016; the dromaeosaurid Acheroraptor temertyorum Evans, Currie, & Larson, 2013; the ankylosaurid Zuul crurivastator Arbour & Evans, 2017; and the troodontid Albertavenator curriei Evans, Cullen, Larson, & Rego, 2017. Evans has also been involved with the naming of various new non-dinosaurian taxa, such as the Devonian onychodontiform fish Onychodus eriensis Mann, Rudkin, Evans, & Laflamme, 2017; the Carboniferous parareptile Erpetonyx arsenaultorum Modesto, Scott, MacDougall, Sues, Evans, & Reisz, 2015; and the Cretaceous baenid turtle Neurankylus lithographicus Larson, Longrich, Evans, & Ryan, 2013. As a professor at the University of Toronto, Evans supervises numerous graduate students in the Department of Ecology & Evolutionary Biology. Former M.Sc. students include Arjan Mann (Carleton University); Ryan Schott (National Museum of Natural History); Chris McGarrity (Field Museum); and Collin Van Buren (Ohio State University).
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By the early 21st century, the prevailing theories were that the family was the sister group of either the Marginocephalia (which includes pachycephalosaurids and ceratopsians), or the Cerapoda (the former group plus ornithopods), or as one of the most basal radiations of ornithischians, before the split of the Genasauria (which includes the derived ornithischians). Heterodontosauridae was defined as a clade by Sereno in 1998 and 2005, and the group shares skull features such as three or fewer teeth in each premaxilla, caniniform teeth followed by a diastema, and a jugal horn below the eye. In 2006, palaeontologist Xu Xing and colleagues named the clade Heterodontosauriformes, which included Heterodontosauridae and Marginocephalia, since some features earlier only known from heterodontosaurs were also seen in the basal ceratopsian genus Yinlong. Timelapse video showing the construction of a model built around a skull cast, including musculature Many genera have been referred to Heterodontosauridae since the family was erected, yet Heterodontosaurus remains the most completely known genus, and has functioned as the primary reference point for the group in the palaeontological literature.
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Restoration of a pair Rauhut and colleagues in 2005 noted that the tendency towards shorter- necks seen in dicraeosaurids, and most evident in Brachytrachelopan, runs counter to the lengthening of the neck seen in most sauropod lineages (brachiosaurids, titanosaurs, diplodocids, etc.) and indicates that this group of sauropods was "progressively adapting for low browsing and might have been specialized on specific food sources, as has been suggested for Amargasaurus and Dicraeosaurus." Moreover, the morphology of the cervical neural arches in Brachytrachelopan would have significantly restricted dorsal flexion of neck and most likely indicates that this sauropod was specialized to a diet of plants "growing at heights of between about 1 and 2 m." Rauhut and colleagues also suggested that diet may have been a limiting factor in body size among dicraeosaurids, and that this may have placed them in the same ecological niche as "large low-browsing iguanodontian ornithopods." Such large iguanodontians are absent from the Late Jurassic Gondwanan sediments that have produced all known fossils of dicraeosaurids, while they are abundant in similar ecosystems of the same age in North America, where dicraeosaurids are absent.
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Fossil, Royal Ontario Museum Paleontologist William Parks described skeleton ROM 804 in 1926 as Thescelosaurus warreni, which had in 1922 been discovered in what was then called the Edmonton Formation near Rumsey Ferry on the Red Deer River. When found, it consisted of a partial skull missing the beak region, most of the left pectoral girdle (including a suprascapula, a bone more commonly found in lizards, but which is believed to have been present in cartilaginous form in some ornithopods due to the roughened ends of their scapulae), the left arm except the hand, ribs and sternal elements, a damaged left pelvis, right ischium, the left leg except for some toe bones, articulated vertebrae from the back, hip, and tail, and a number of ossified tendons that sheathed the end of the tail. The body of the animal had fallen on its left side, and most of the right side had been destroyed before burial; in addition, the head had been separated from the body, and the neck lost. Parks differentiated the new species from T. neglectus by leg proportions; T. warreni had a longer tibia than femur, and longer toes.
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