Aside from the dinosaur lineage that evolved to become birds, two other major groups of dinosaurs — the plant-eating hadrosaurs and ceratopsians — remained strong until the asteroid struck.
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Triceratops was among the largest of four-legged horned dinosaurs called ceratopsians, reaching up to about 30 feet (9 meters) long, with horns above its eyes and nose, and a bony shield protecting its neck.
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Both dinosaurs were members of a group called ceratopsians that included the well-known Triceratops, typically possessing parrot-like beaks to crop low-growing herbs and shrubs, a bony neck shield, or frill, and forward-pointing facial horns.
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Ceratopsians, famous for Protoceratops, Triceratops and Styracosaurus illustrate the evolution of frilled and horned skulls. The frills evolved from the shelf common to all Marginocephalia. Ceratopsians are separated into basal ceratopsians, including the parrot- beaked Psittacosaurus, and neoceratopsians. Diversity of ceratopsian skulls.
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Dinosaur Hall - Diatryma at azmnh.org As sauropods they have a Camarasaurus skeleton and an Apatosaurus femur.Dinosaur Hall - Sauropods at azmnh.org As ceratopsians they have a Psittacosaurus skeleton, a Zuniceratops, Protoceratops, Pentaceratops and TriceratopsDinosaur Hall - Ceratopsians at azmnh.
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Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.
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Ceratopsians probably had the "low mass-specific metabolic rat[e]" typical of large bodied animals.
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Zuniceratops was a herbivore like other ceratopsians and was probably a herd animal as well.
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William Morrow:New York, p. 438. These facts indicate that some ceratopsians were the dominant herbivores in their environments. Some species of ceratopsians, especially Centrosaurus and its relatives, appear to have been gregarious, living in herds. This is suggested by bonebed finds with the remains of many individuals of different ages.
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Footprints discovered in the formation include those of theropods, hadrosaurs, ceratopsians, ankylosaurs, pterosaurs and birds, notably the Magnoavipes denaliensis.
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Reconstructed skeletons of an adult with juveniles P. sibiricus skull in front view Psittacosaurus is the type genus of the family Psittacosauridae, which was also named by Osborn in 1923. Psittacosaurids were basal to almost all known ceratopsians except Yinlong and perhaps the Chaoyangsauridae. While Psittacosauridae was an early branch of the ceratopsian family tree, Psittacosaurus itself was probably not directly ancestral to any other groups of ceratopsians. All other ceratopsians retained the fifth digit of the hand, a plesiomorphy or primitive trait, whereas all species of Psittacosaurus had only four digits on the hand.
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Ceratops, like all ceratopsians, was a herbivore biting off plant material with its beak and processing it with its tooth batteries.
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The suffix common among ceratopsians, "ceratops", means "horned face". It was named in reference to its lack of a nasal horn.
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As Protoceratops is a relatively basal member of the ceratopsians, the finding also suggests that other ceratopsians provided care for their young as well. Studies of lines of growth (i.e. lines of von Ebner) of the teeth in embryonic P. andrewsi suggests plesiomorphically long incubation times, with a minimum incubation time of 83.16 days for P. andrewsi.
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Pachycephalosaurs had gastroliths to help in digestion of food, but only primitive ceratopsians, such as Psittacosaurus, have been found to have gastroliths.
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Ceratopsid skulls at the Natural History Museum of Utah In clade-based phylogenetic taxonomy, Ceratopsia is often defined to include all marginocephalians more closely related to Triceratops than to Pachycephalosaurus. Under this definition, the most basal known ceratopsians are Yinlong, from the Late Jurassic Period, along with Chaoyangsaurus and the family Psittacosauridae, from the Early Cretaceous Period, all of which were discovered in northern China or Mongolia. The rostral bone and flared jugals are already present in all of these forms, indicating that even earlier ceratopsians remain to be discovered. The clade Neoceratopsia includes all ceratopsians more derived than psittacosaurids.
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Most restorations of ceratopsians show them with erect hindlimbs but semi-sprawling forelimbs, which suggest that they were not fast movers. But Paul and Christiansen (2000) argued that at least the later ceratopsians had upright forelimbs and the larger species may have been as fast as rhinos, which can run at up to 56 km or 35 miles per hour.
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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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Reconstructed skull Zuniceratops is an example of the evolutionary transition between early ceratopsians and the later, larger ceratopsids that had very large horns and frills. This supports the theory that the lineage of ceratopsian dinosaurs may have been North American in origin. Although the first specimen discovered had single-rooted teeth (unusual for ceratopsians), later fossils had double-rooted teeth. This is evidence that the teeth became double-rooted with age.
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The largest ceratopsian known is Triceratops horridus, along with the closely related Eotriceratops xerinsularis both with estimated lengths of . Ojoceratops and several other ceratopsians rival them in size.
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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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Olmos Formation stratigraphic column in Texas The Olmos Formation is a geologic formation in Mexico. It preserves fossils of plants, hadrosaurs, ceratopsians and tyrannosaurs dating back to the Cretaceous period.
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Duckbilled hadrosaurs were common inhabitants of Montana's Campanian coastal plains. Maiasaura is one example. Montana has an especially good fossil record of ceratopsid dinosaurs. Examples of contemporary local ceratopsians include Einiosaurus.
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Although ceratopsians have been found all over the world, protoceratopsids are only known from Asia, with most specimens found in China and the Nemegt Basin in Mongolia. As ceratopsians, protoceratopsids were herbivorous, with constantly replacing tooth batteries made for slicing through plants and a hooked beak for grabbing them. Protoceratopsids were relatively small, between 1-2.5 m in length from head to tail. Their bony frill and horns were much smaller than more derived members of Ceratopsia.
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This is presumed to have been useful for breaking down tough vegetation through bacterial fermentation. Another adaptation for advanced vegetation digestion is seen in Ceratopsians, which evolved features to improve their chewing apparatus. Derived ceratopsians have vertical grinding surfaces on their teeth to maximize break-down of tough vegetation. There is also evidence of advanced adductor musculature that extends from a large coronoid process on the mandible up to the ceratopsian frill, which would increase chewing force.
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In 1932, Charles Mortram Sternberg reported the presence of the footprints of a large, four-footed dinosaur from Lower Cretaceous rocks in British Columbia, Canada. He described a new ichnogenus and species for these tracks, Tetrapodosaurus borealis, and attributed them to ceratopsians. However, in 1984 paleontologist Kenneth Carpenter re-examined the British Columbian Tetrapodosaurus prints and argued that they were made by ankylosaurs rather than ceratopsians. Specifically, Carpenter concluded that these were probably the footprints of Sauropelta.
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Other dinosaurs known from the Oldman Formation include the hadrosaur Brachylophosaurus, the ceratopsians Coronosaurus and Albertaceratops, ornithomimids, therizinosaurs and possibly ankylosaurs. Theropods included troodontids, oviraptorosaurs, the dromaeosaurid Saurornitholestes and possibly an albertosaurine tyrannosaur.
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Berkeley: University of California Press. Pp. 494-513. The epoccipital is a distinctive bone found lining the frills of ceratopsians. The name is a misnomer, as they are not associated with the occipital bone.
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Judiceratops tigris Judiceratops shared its paleoenvironment with bony fishes, amphibians, the Choristoderan Champsosaurus, the hadrosaur Brachylophosaurus canadensis, the pachycephalosaur Colepiocephale lambei, the theropods Dromaeosaurus, Gorgosaurus and Troodon, and with fellow ceratopsians Albertaceratops, Medusaceratops and Avaceratops.
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The taxon Protoceratopsidae was introduced by Walter W. Granger and William King Gregory in May 1923 as a monotypic family for Protoceratops andrewsi. Granger and Gregory recognized Protoceratopss close relationship to other ceratopsians, but considered it primitive enough to warrant its own family, and perhaps suborder. Protoceratopsidae was later expanded to include all ceratopsians that were too advanced to be psittacosaurids, but too primitive to be ceratopsids. In 1998, Paul Sereno defined Protoceratopsidae as the stem-based clade including "all coronosaurs closer to Protoceratops than to Triceratops".
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The Albian Zhonggou Formation slightly overlains the sediments of the Xiagou Formation, and consists of abundant red fluvial sedimentation. Aside from the referred specimen of Suzhousaurus, sparse remains of Auroraceratops and Beishanlong are known from the red beds. The remains of ceratopsians and therizinosaurs in these beds could reflect a preference of niches close to rivers and lakes, whereas hadrosauroids and sauropods probably inhabited more interior environments of the region. However, ceratopsians and therizinosaurs remains are also found in the gray-variegated beds of the Yujingzi Basin.
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They found that display patterns diverged widely overall while those of sympatric species did not differ significantly from those of non-sympatric species, concluding that the hypothesis did not have statistical support among ceratopsians. In 2015, biologist Pasquale Raia and colleagues examined the evolutionary increase in the complexity and size of animal ornaments (such as crests, horns, and tusks) over time, using ammonites, deer, and ceratopsians as examples. Frill complexity in ceratopsians appeared to have increased in more recent species, and Kosmoceratops had the highest values of fractal dimensions in its neck frill margin (followed by Styracosaurus, Diabloceratops, and Centrosaurus). The authors found that ornament complexity increased with body size, suggesting that the evolution of ornament complexity was a byproduct of Cope's rule (which postulates that population lineages tend to increase in body size over evolutionary time).
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The frills also could have been used for species recognition purposes, as they seem to develop fairly early in life. There has also been evidence that ceratopsians care for their young, as bone-beds have been found of adult individuals with a nest of juveniles, although some refute this as viable evidence of care for young. There have also been bone-beds found with hundreds of adult ceratopsians, indicating herd activity. A few specimens have been found with puncture wounds, supporting the use of horns as protective or combative weapons.
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In addition, the antorbital fenestra, an opening in the skull between the eye socket and nostril, was lost during the evolution of Psittacosauridae, but is still found in most other ceratopsians and in fact most other archosaurs. It is considered highly unlikely that the fifth digit or antorbital fenestra would evolve a second time. In 2014, the describers of a new taxon of basal ceratopsian published a phylogenetic analysis encompassing Psittacosaurus. The below cladogram is from their analysis, placing the genus as one of the most primitive ceratopsians.
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The skeleton mounted in the Smithsonian Among the five original specimens parts of three skulls were discovered, detached from their owner's body and fragmented. Despite this, the skull showed that the animal had only small bumps over the eyes rather than full-grown horns like in the more famous ceratopsians such as Triceratops. The nasal horn was thick and low, while its neck frill was moderately large. Unfortunately the specimens were incomplete so it cannot be determined if there were parietal openings in the frill like some other ceratopsians possessed.
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Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. They have been reported from ceratopsians, hadrosaurs and other tyrannosaurs. Tyrannosaurid bones with tooth marks represent about 2% of known fossils with preserved tooth marks.Jacobsen, A.R. 2001.
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There is still no sign of the bony neck frill or prominent facial horns which would develop in later ceratopsians. Bony horns protrude from the skull of P. sibiricus, but these are thought to be an example of convergent evolution.
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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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There Kritosaurus, Parasaurolophus and Pentaceratops are the dominant fauna. The giant eusuchian Deinosuchus is also "conspicuous" in the southern biome. Farther south, in Texas, Kritosaurus predominates. The biomes of the Eastern US may have resembled those of Texas except completely lacking in ceratopsians.
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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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Yinlong was discovered with seven gastroliths preserved in the abdominal cavity. Gastroliths, stones stored in the digestive tract and used to grind plant material, are also found in other ceratopsians such as Psittacosaurus, and are also widely distributed in most other dinosaur groups, including birds.
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500px Marginocephalia are named for a shelf that projects over the back of the skull. They include the pachycephalosaurians and ceratopsians. Pachycephalosaurs are best known for their thick upper fronts to their skull. The oldest known is Stenopelix, from the early Cretaceous of Europe.
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Life reconstruction of Linheraptor in its arid desert habitat. Linheraptor was a bird-like theropod dinosaur. It was a dromaeosaurid which measured approximately in length, and weighed up to approximately . At that size, Linheraptor would have been a fast and agile predator, perhaps preying on small ceratopsians.
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Microceratus belonged to the Ceratopsia (Ancient Greek for "horned face"), a group of herbivorous dinosaurs with parrot-like beaks which thrived in North America and Asia during the Cretaceous Period, which ended roughly 66 million years ago. All ceratopsians became extinct at the end of this era.
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Possible ceratopsians from the Southern Hemisphere include the Australian Serendipaceratops, known from an ulna, and Notoceratops from Argentina is known from a single toothless jaw (which has been lost).Rich, T.H. & Vickers- Rich, P. 2003. Protoceratopsian? ulnae from the Early Cretaceous of Australia. Records of the Queen Victoria Museum.
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This posture is also seen in ankylosaurs, ceratopsians, and the early cynodont Procynosuchus. Several aspects of the forelimbs have been interpreted as adaptations to digging. Like many digging tetrapods, the radius is significantly shorter than the humerus. Like other aetosaurs, there is a prominent deltopectoral crest on the humerus.
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Kulceratops is a genus of ceratopsian dinosaur from the Early Cretaceous. It lived in the late Albian stage. It is one of the few ceratopsians known from this period. However, the fossils from this genus have been sparse: only jaw and tooth fragments have been found so far.
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Estimated size of Eotriceratops (green) beside a Triceratops (blue) and a human The holotype skull has been estimated to have had an original length of around . It has been estimated that this specimen had a total length of about . In 2010, Paul estimated its length at 8.5 metres, while its weight estimated at ten tonnes. This qualifies Eotriceratops as one of the largest ceratopsians, rivalled only by Triceratops horridus at 8 m (26 ft) and 9–13.5 t (9.9–14.9 short tons), and the ichnogenus Ceratopsipes, thought to be as large as 12 m (39.4 ft) and 18 tons Eotriceratops differs from other chasmosaurine ceratopsians in unique features of the skull bones.
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Other research examining juvenile ceratopsians reveals a change in horn morphology over time, suggesting frills and horns could have been used for intraspecific communication of age. Horns also could have been used for thermoregulation as indicated by isotope analysis, as aid in knocking down vegetation, or for horn-locking agonistic behavior.
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Michael J. Benton, Mikhail A. Shishkin, David M. Unwin, The Age of Dinosaurs in Russia and Mongolia, Cambridge University Press, 04/12/2003 - 740 páginas It is larger than some contemporary dinosaur species. Some researchers have even suggested that it could have predated on the local small ceratopsians such as Asiaceratops.
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Small coelurosaurians are the most diverse dinosaurs, including fellow dromaeosaurid Velociraptor, troodontids Byronosaurus and Saurornithoides, oviraptorids Citipati, Khaan, and Oviraptor, and alvarezsaurs Kol and Shuvuuia; other dinosaurs present included ceratopsians Protoceratops and Udanoceratops, the hadrosaur Plesiohadros, and the ankylosaurid Pinacosaurus. Like other dromaeosaurids, Mahakala would have been a small active predaceous carnivore.
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Asiaceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads, and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles.
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Microceratus, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles.
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Dinosaurs and land plants. In: Friis, E. M., Chaloner, W. G., and Crane, P. R. (eds.) The Origins of Angiosperms and their Biological Consequences Cambridge University Press, pp. 225–258. . Dodson has proposed that Late Cretaceous ceratopsians may have knocked down angiosperm trees and then sheared off leaves and twigs.Dodson, P. (1996).
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Prenoceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles.
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A small rostral bone on the end of the upper jaw clearly identifies Yinlong as a ceratopsian, although the skull displays several features, especially the ornamentation of the squamosal bone of the skull roof, which were previously thought to be unique to pachycephalosaurians. The presence of these features in Yinlong indicates these as actual synapomorphies (unique features) of the larger group Marginocephalia, which contains both the pachycephalosaurs and the ceratopsians, although these features have been lost in all known ceratopsians more derived than Yinlong. The addition of these characters further strengthens the support for Marginocephalia. Yinlong also preserves skull features reminiscent of the family Heterodontosauridae, providing support for the hypothesis that heterodontosaurids are closely related to marginocephaliansZhao X., Cheng Z., & Xu X. 1999.
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One of the basalmost members of this group is Psittacosaurus, which is one of the most species-rich dinosaur genera from Asia. Ceratopsians later evolved into very large quadrupeds with elaborate facial horns such as Triceratops, Styracosaurus, and Centrosaurus. There was no change in richness of species throughout the Cretaceous before the Cretaceous-Paleogene extinction.
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Biogeography of centrosaurine dinosaurs during the Campanian The evolutionary origins of Styracosaurus were not understood for many years because fossil evidence for early ceratopsians was sparse. The discovery of Protoceratops, in 1922, shed light on early ceratopsid relationships,Dodson, P. (1996). The Horned Dinosaurs: A Natural History. Princeton University Press: Princeton, New Jersey, p. 244. .
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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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Kulceratops, like all ceratopsians, was a herbivore. During the early Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles.
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The program features the age of dinosaurs, from the appearing of the early forms like Herrerasaurus, to the Tyrannosaurus and Ceratopsians of the late Cretaceous. The possibilities whether dinosaurs were active, warm-blooded animals, had parental care, and the theory that they are the ancestors to birds are featured. What caused their extinction is also discussed.
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Ceratopsian fossil discoveries. The presence of Jurassic ceratopsians only in Asia indicates an Asian origin for the group, while the more derived ceratopsids occur only in North America save for one Asian species. Questionable remains are indicated with question marks. Ceratopsia appears to have originated in Asia, as all of the earliest members are found there.
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Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. They have been reported from ceratopsians, hadrosaurs and other tyrannosaurs. Tyrannosaurid bones with tooth marks represent about 2% of known fossils with preserved tooth marks. Tyrannosaurid teeth were used as holdfasts for pulling meat off a body, rather than knife-like cutting functions.
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Protoceratopsids have a frill and rostral bone characteristic of all ceratopsians. Their snout is particularly wedge-shaped with tall and narrow nostrils situated high on it. The antorbital fenestra is unusually small, and the antorbital fossa sits high on the skull with a slit connecting it to a sinus in the maxilla. This sinus is unique to Protoceratopsidae.
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Ceratopsians originated in Asia and had two major dispersal events. The first was the migration of Leptoceratopsidae's ancestor through Europe and into North America. The second dispersal was 15 million years later, this time of Ceratopsidae's ancestors across the Bering Land Bridge into North America between 120Ma and 140Ma. Protoceratopsids are found in Asia but not North America.
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Sternberg thought the horns of ceratopsians helped defend against predators. In 1961, Davitashvili proposed that ceratopsids used their horns and frills to compete over mates. Farlow and Dodson arrived at the same conclusion in the 1970s, and were followed by Ralph Molnar. Ostrom, who had previously followed the jaw musculature interpretation, came to support this view in 1986.
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Finally, in Europe, dromaeosaurids, rhabdodontid iguanodontians, nodosaurid ankylosaurians, and titanosaurian sauropods were prevalent. Flowering plants were greatly radiating, with the first grasses appearing by the end of the Cretaceous. Grinding hadrosaurids and shearing ceratopsians became extremely diverse across North America and Asia. Theropods were also radiating as herbivores or omnivores, with therizinosaurians and ornithomimosaurians becoming common.
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Restoration of a resting individual Turanoceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles.
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Archaeoceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp beak to bite off the leaves or needles and chop them up to be swallowed.
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Arrhinoceratops lived in a wet coast- land with warm summers but cool winters. It was likely preyed upon by Albertosaurus. Arrhinoceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers.
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In the Late Cretaceous, the hadrosaurs, ankylosaurs, and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). Tyrannosaurs dominated the large predator niche in North America. They were also present in Asia, although were usually smaller and more primitive than the North American varieties. Pachycephalosaurs were also present in both North America and Asia.
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These new branches on the dinosaur family tree led to well-known dinosaur groups, such as the horned ceratopsians, armoured stegosaurs, and tyrannosaurs. Clark joined Xu, from Beijing’s Institute of Vertebrate Paleontology and Paleoanthropology, to explore the Junggar Basin, and in particular the Shishugou Formation, where the exposed rocks have been linked to the Middle Jurassic.
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Avaceratops, like all ceratopsians, was a herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape", so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the leaves or needles. The habitat of Avaceratops was heavily forested and wet.
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Theropods included the tyrannosaurs Albertosaurus, Gorgosaurus, Daspletosaurus, Teratophoneus, Bistahieversor, and Appalachiosaurus, and the dromaeosaurids Dromaeosaurus, Saurornitholestes, Atrociraptor, and Bambiraptor. Ceratopsians, such as Pachyrhinosaurus, Styracosaurus, Centrosaurus, Monoclonius, Brachyceratops and Pentaceratops also existed. Among hadrosaurs, Hypacrosaurus, Gryposaurus, Kritosaurus, Parasaurolophus, Corythosaurus, Lambeosaurus and Prosaurolophus existed. During the latest Cretaceous, the Maastrichtian age, the diversity of dinosaurs saw a decline from the preceding Campanian stage.
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Chasmosaurus ( ) is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings (fenestrae) in its frill (Greek chasma meaning 'opening' or 'hollow' or 'gulf' and sauros meaning 'lizard'). With a length of and a weight of , Chasmosaurus was a ceratopsian of average size. Like all ceratopsians, it was purely herbivorous.
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The skin of ceratopsians consisted of large polygonal scales, sometimes with scattered circular plates. See also image at "Mummified" remains and skin impressions of hadrosaurids reveal pebbly scales. It is unlikely that the ankylosaurids, such as Euoplocephalus, had insulation, as most of their surface area was covered in bony knobs and plates. Likewise there is no evidence of insulation in the stegosaurs.
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Archaeoceratops, meaning "ancient horned face", is a genus of basal neoceratopsian dinosaur from the Early Cretaceous (Aptian stage) of north central China. It appears to have been bipedal and quite small (about 1 meter long) with a comparatively large head. Unlike many later ceratopsians it had no horns, possessing only a small bony frill projecting from the back of its head.
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Chaoyangsaurus ("Chaoyang lizard") was a marginocephalian dinosaur from the Late Jurassic of China (dated to between 150.8 and 145.5 million years ago).Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix. Chaoyangsaurus belonged to the Ceratopsia (Greek for "horned faces"), Chaoyangsaurus, like all ceratopsians, was primarily a herbivore.
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Dinosaurs that have been given as evidence of biogeography include abelisaurid theropods from South America and possibly elsewhere on Gondwana. Relationships between dinosaurs show abundant evidence of dispersal from one region of the globe to another. Tetanuran theropods travelled widely through western North America, Asia, South America, Africa and Antarctica. Pachycephalosaurs and ceratopsians show clear evidence of multiple bidirectional dispersion events across Beringia.
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Gradually however "relict" dinosaurs such as protoceratopsids and sauropods began expanding into lower altitude areas as sea-levels fell. In the southern biome by Lancian time sauropods had replaced both hadrosaurs and ceratopsians in the southern biome. In the north both were still present although hadrosaurs were demoted to a "subordinate" role in dinosaur ecosystems. Edmontosaurus was the dominant northern hadrosaurid.
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Dinosaur faunas of the Judithian age may represent the peak of dinosaur evolution in North America. Hadrosaurs were universally the dominant herbivore of the period and comprised more than half of "a typical assemblage." This was also the period of greatest generic diversity among large herbivorous dinosaurs. Just in Montana and Southern Alberta were ten genera of ceratopsians and ten genera of hadrosaurs.
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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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Montanoceratops shared the paleoenvironment of the St. Mary River Formation with other dinosaurs, such as the ceratopsians Anchiceratops and Pachyrhinosaurus canadensis, the armored nodosaur Edmontonia longiceps, the duckbilled hadrosaur Edmontosaurus regalis, the theropods Hagryphus, Saurornitholestes and Troodon, and the tyrannosaurid Albertosaurus which was likely the apex predator in its ecosystem."Alberta, Canada; 13. St. Mary River Formation," in Weishampel, et al. (2004). Pages 577-578.
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Journal of Vertebrate Paleontology 30 (Supplement 2): 55A. The saltwater plesiosaur Leurospondylus was present and freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. Evidence has shown that multituberculates and the early marsupial Didelphodon coyi were present. Vertebrate trace fossils from this region included the tracks of theropods, ceratopsians and ornithopods, which provide evidence that these animals were also present.
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Previously, the origins of Triceratops were poorly known. Until the description of Titanoceratops, Eotriceratops was the oldest known triceratopsin, and only dated to 68 million years old, from the uppermost region of the Horseshoe Canyon Formation. No Campanian triceratopsins were known, so it appeared as if the group evolved in the Maastrichtian. Titanoceratops shows that large-bodied ceratopsians evolved millions of years earlier than thought.
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P. mongoliensis specimen AMNH 6254 with gastroliths in its stomach region, American Museum of Natural History. Psittacosaurs had self-sharpening teeth that would have been useful for cropping and slicing tough plant material. Unlike later ceratopsians, they did not have teeth suitable for grinding or chewing their food. Instead, they used gastroliths—stones swallowed to wear down food as it passed through the digestive system.
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Conifers were apparently the dominant canopy plants, with an understory of ferns, tree ferns, and angiosperms. Dinosaur Park is known for its diverse community of herbivores. As well as Stegoceras, the formation has also yielded fossils of the ceratopsians Centrosaurus, Styracosaurus and Chasmosaurus, the hadrosaurids Prosaurolophus, Lambeosaurus, Gryposaurus, Corythosaurus, and Parasaurolophus, and the ankylosaurs Edmontonia and Euoplocephalus. Theropods present include the tyrannosaurids Gorgosaurus and Daspletosaurus.
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Pachycephalosaurs are today grouped with the horned ceratopsians in the group Marginocephalia. Stegoceras itself has been considered basal (or "primitive") compared to other pachycephalosaurs. Stegoceras was most likely herbivorous, and it probably had a good sense of smell. The function of the dome has been debated, and competing theories include use in intra-specific combat (head or flank-butting), sexual display, or species recognition.
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Turanoceratops ("Turan horned face") is a genus of herbivorous ceratopsian dinosaur from the late Cretaceous Bissekty Formation of Uzbekistan. The fossils dated from the mid-late Turonian stage, roughly 90 million years ago. The skull bore a pair of long brow horns like those seen in the Ceratopsidae, although Turanoceratops appears to have been transitional between earlier ceratopsians and ceratopsids, and not a ceratopsid itself.
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Microceratus (meaning "small-horned") is a genus of small ceratopsian dinosaur that lived in the Cretaceous period in Asia. It walked on two legs, had short front arms, a characteristic ceratopsian frill and beak-like mouth, and was around long. It was one of the first ceratopsians, or horned dinosaurs, along with Psittacosaurus in Mongolia. The type species, Microceratops gobiensis, was first described by Bohlin in 1953.
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The Two Medicine Formation was deposited at higher elevations farther inland than the other two formations. Oviraptorosaurs like Caenagnathus and Chirostenotes may have preyed upon the ornithopod Orodromeus. A large variety of ceratopsians coexisted in this region, which included Achelousaurus, Brachyceratops, Cerasinops, Einiosaurus, Prenoceratops and Rubeosaurus. Carnivores included an unnamed troodontid, possibly Stenonychosaurus, the dromaeosaurs Bambiraptor and Saurornitholestes, and the large tyrannosaurids Daspletosaurus and Gorgosaurus.
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Like other ceratopsians, this dinosaur may have been a herd animal, travelling in large groups, as suggested by bonebeds. Named by Lawrence Lambe in 1913, Styracosaurus is a member of the Centrosaurinae. One species, S. albertensis, is currently assigned to Styracosaurus. Another species, S. ovatus, named in 1930 by Charles Gilmore was reassigned to a new genus, Rubeosaurus, by Andrew McDonald and Jack Horner in 2010.
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Indiana University Press. Hardbound: 634 pp. This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Nasutoceratops shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus.
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The specific name means "the fat one" in Latin. Since the ceratopsians had not been recognised yet as a distinctive group, Cope was uncertain about much of the fossil material, not recognizing the nasal horn core, nor the brow horns, as part of a fossil horn. The skull frill he interpreted as an episternum, an ossified part of the breastbone, and the fused cervicals he assumed to be anterior dorsals.
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Foot bones Another unusual feature was the presence of tall spines on the bones of the tail. Although these would not have been visible during life, they would have made the tail unusually deep in cross-section. Since the tail was also highly flexible, it is possible that it was used in intra-species signalling, and that the deep shape made it more visible. Montanoceratops, like all Ceratopsians, was a herbivore.
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The fishes are represented by the two species Melvius chauliodous and Myledalphus bipartitus. The crurotarsans include Brachychampsa montana and Denazinosuchus kirtlandicus. Ornithischians from the formation are represented by the hadrosaurids Anasazisaurus horneri, Naashoibitosaurus ostromi, Kritosaurus navajovius, and P. tubicen; the ankylosaurids Ahshislepelta minor and Nodocephalosaurus kirtlandensis; the ceratopsians Pentaceratops sternbergii and Titanoceratops ouranos; and the pachycephalosaurs Stegoceras novomexicanum and Sphaerotholus goodwini. Saurischians include the tyrannosaurid Bistahieversor sealeyi; the ornithomimid Ornithomimus sp.
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Teratophoneus curriei shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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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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However, there is general agreement that some behaviors which are common in crocodiles and birds, dinosaurs' closest living relatives, were also common among dinosaurs. Gregarious behavior was common in many dinosaur species. Dinosaurs may have congregated in herds for defense, for migratory purposes, or to provide protection for their young. There is evidence that many types of dinosaurs, including various theropods, sauropods, ankylosaurians, ornithopods, and ceratopsians, formed aggregations of immature individuals.
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Cross section of a typical theropod dinosaur tooth in side view. All dinosaur teeth possess the same tissue types but can differ in their appearance. Various major groups of dinosaurs have been examined through histology, these include the carnivorous theropods and herbivorous groups such as the sauropods, hadrosaurs and ceratopsians. Listed below are some of the dental anatomy that has been identified through histology and interpretations on their significance.
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One ankylosaurian and two nodosaurians are known, Ankylosaurus, Denversaurus and possibly Edmontonia. Multiple genera of ceratopsians are known from the formation, the leptoceratopsid Leptoceratops and the chasmosaurines Nedoceratops, Torosaurus, Triceratops, and Tatankaceratops. Hadrosaurs are common in the Hell Creek Formation, and are known from multiple species of the ornithopod Thescelosaurus, and the hadrosaurids Edmontosaurus, and an undescribed genus similar to Parasaurolophus. Five pachycephalosaurians have been found in the Hell Creek Formation.
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The frills of ceratopsians are incredibly diverse. They may have been used for protective purposes as the frill sometimes splays over the neck. However, some say that the frill would have provided little protection from other large dinosaurs such as Tyrannosaurus. Other possible functions include intraspecific communication for mating purposes or as a visual display of territorial protection, as seen in many common day organisms such as red-breasted robins.
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Like many ceratopsians, Chasmosaurus had three main facial horns - one on the nose and two on the brow. In both species these horns are quite short, but with C. russelli they are somewhat longer, especially the brow horns, and more curved backwards. The frill of Chasmosaurus is very elongated and broader at the rear than at the front. It is hardly elevated from the plane of the snout.
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By the late Cretaceous, titanosaurs were the dominant group of neosauropods, especially on the southern continents. In North America and Asia, much of their role as large herbivores had been supplanted by hadrosaurs and ceratopsians, although they remained in smaller numbers all the way until the Cretaceous-Paleogene extinction.Lehman, T. M., 2001, Late Cretaceous dinosaur provinciality: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press.
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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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Hagryphus shared its paleoenvironment with theropods such as dromaeosaurids, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, and the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, metatherians, and eutherians.
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This list of marginocephalian type specimens is a list of fossils serving as the official standard-bearers for inclusion in the species and genera of the dinosaur clade Marginocephalia, which includes the thick-headed pachycephalosaurs and the horned ceratopsians. Type specimens are those which are definitionally members of biological taxa and additional specimens can only be "referred" to these taxa if an expert deems them sufficiently similar to the type.
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The fossil record, systematics and evolution of pachycephalosaurs and ceratopsians from Asia. 480–516 in Benton, M.J., M.A. Shishkin, D.M. Unwin & E.N. Kurochkin (eds.), The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge. The dome- headed/flat-headed division of the pachycephalosaurs was abandoned in the following years, as flat heads were considered paedomorphic (juvenile-like) or derived traits in most revisions, but not a sexually dimorphic trait.
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Size compared to a human Achelousaurus is estimated to have been long with a weight of . The skull of an adult individual (holotype specimen MOR 485) was estimated to have been long. This puts it in the same size-range as other members of the Centrosaurinae subgroup of ceratopsians that lived during the Campanian age. It was about as large as its close relative Einiosaurus, but with a much heavier build.
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The biomes of the Eastern US may have resembled those of Texas except completely lacking in ceratopsians. Parasaurolophus and Kritosaurus are also present in northern latitudes, so evidently exchange between them occurred, but both are uncommon outside of the southern biome. In the south, little changes in the transition to the Edmontonian. However, in the northern biome a general trend in reduction of centrosaurines, with only pachyrhinosaurus surviving.
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Prismatoolithids were previously hypothesized to be eggs of hypsilophodonts or ceratopsians, but later research found that they in fact are the eggs of theropods, based on analysis of preserved embryos of Prismatoolithus levis which showed them to be Troodon formosus. Therefore, Trigonoolithus was also probably laid by a theropod. Based on its phylogenetic position, Moreno-Azanza et al. concluded it was most likely a non-dromaeosaurian, non-oviraptorid coelurosaur theropod dinosaur.
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They noted that many large ceratopsians had openings in their frills, making them of little use in defense, and that the wide variety in the size and orientation of their horns did not have an obvious function in combat. They also pointed out that there is little evidence for sexual dimorphism in ceratopsians. Responding to Padian and Horner the same year, paleontologist Rob J. Knell and Sampson argued that while species recognition could have been a secondary function of "bizarre structures", sexual selection (used in display or combat to compete for mates) was a more likely explanation because of the high cost of developing them and how they appeared to be highly variable within species. They also pointed out that a lack of sexual dimorphism does not preclude the use of horns in mate competition; male bovines use their horns for this purpose while females use them primarily for defense and secondarily for sexual selection.
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In 2013, paleontologists David E. Hone and Darren Naish criticized the "species recognition hypothesis", arguing that no extant animals use such structures primarily for species recognition and that Padian and Horner had ignored the possibility of mutual sexual selection (where both sexes are ornamented). They noted that if the primary purpose of the structures was species recognition, they would have differed in the shape of a single structure because additional structures would have been redundant at additional cost. Ceratopsians, for example, had elaborate nasal horn, brow horn, jugal boss, frill midline, and frill edge features, as well as differences in body size and proportions, while the absence or presence of a single horn would have been enough to differentiate between sympatric species. In 2018, paleontologist Andrew Knapp and colleagues examined whether the diverging ornamental traits of ceratopsians were correlated with sympatricity between two or more species, as would be predicted by the "species recognition hypothesis".
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Flat- headed pachycephalosaur speciments have been found in Asia, and there is great controversy on the meaning of these flat heads. Recent research suggests the flat heads could be a juvenile state before developing the dome shape in the adult stage. It could also be evidence of sexual dimorphism with the female being more flat-headed. Ceratopsians, or "horned-faces", differ from pachycephalosaurs in the presence of a rostral bone, or beak.
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Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons.(published abstract only) There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including ceratopsians and hadrosaurs. However, only rarely are so many dinosaurian predators found at the same site. Small theropods like Deinonychus, Coelophysis and Megapnosaurus (Syntarsus rhodesiensis) have been found in aggregations, as have larger predators like Allosaurus and Mapusaurus.
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Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons.(published abstract only) Model in RTM There is plentiful evidence for gregarious behaviour among herbivorous dinosaurs, including ceratopsians and hadrosaurs. However, only rarely are so many dinosaurian predators found at the same site. Small theropods like Deinonychus and Coelophysis have been found in aggregations, as have larger predators like Allosaurus and Mapusaurus.
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The mammalian turnover was preceded by an episode of immigration, and was associated with the rapid expansion of terrestrial habitat due to melting glaciers. In the mammalian turnover, the newly emerging dominant fauna were clearly Old World immigrants, the cervids and bovids. In the southern biome, by Lancian time sauropods had replaced both hadrosaurs and ceratopsians. In the north, both were still present although hadrosaurs were demoted to a "subordinate" role in dinosaur ecosystems.
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The smallest known species, P. ordosensis, is 30% smaller than P. mongoliensis. The largest are P. lujiatunensis and P. sibiricus, although neither is significantly larger than P. mongoliensis. Psittacosaurus postcranial skeletons are more typical of a 'generic' bipedal ornithischian. There are only four digits on the manus ('hand'), as opposed to the five found in most other ornithischians (including all other ceratopsians), while the four-toed hindfoot is very similar to many other small ornithischians.
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The early 20th century was a fruitful time for ceratopsian research. In 1907, Hatcher and others published a monograph on ceratopsid anatomy that is still considered the single most significant publication on the topic to date. Many new species were being described, including Centrosaurus, Styracosaurus, and Chasmosaurus. Not long after, the Central Asiatic Expedition led by Roy Chapman Andrews of the American Museum of Natural History discovered the primitive ceratopsians Psittacosaurus and Protoceratops in Mongolia.
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Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ' (), meaning "of a bird", and ' (), plural ', meaning "hip joint". However, birds are only distantly related to this group as birds are theropod dinosaurs. Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs (e.g.
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Skeletal restoration. Leptoceratops, like other ceratopsians, would have been a herbivore. The jaws were relatively short and deep, and the jaw muscles would have inserted over the large parietosquamosal frill, giving Leptoceratops a powerful bite. The teeth are unusual in that the dentary teeth have dual wear facets, with a vertical wear facet where the maxillary teeth sheared past the crown, and a horizontal wear facet where the maxillary teeth crushed against the dentary teeth.
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Osborn originally assigned Pentaceratops to Ceratopsia. Within this group Pentaceratops belonged to the Ceratopsinae or Chasmosaurinae. It appears to be most closely related to Utahceratops. Their clade was perhaps more derived than the earlier genus Chasmosaurus but more basal than Anchiceratops, the latter representing a line of which Triceratops was a member, which lived a few million years later, right at the end of the Cretaceous period, when all ceratopsians died out.
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University of Pennsylvania, Philadelphia. 227 pp. OCLC 61500040 It was long believed that ceratopsians like Styracosaurus used their frills and horns in defence against the large predatory dinosaurs of the time. Although pitting, holes, lesions, and other damage on ceratopsid skulls are often attributed to horn damage in combat, a 2006 study found no evidence for horn thrust injuries causing these forms of damage (for example, there is no evidence of infection or healing).
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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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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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Just in Montana and Southern Alberta were ten genera of ceratopsians and ten genera of hadrosaurs. An association between Centrosaurus and Corythosaurus is characteristic of southern Alberta. Earlier research had found that lambeosaurines are less common in contemporary Montanan strata and with different centrosaurs as Monoclonius taking the place of Centrosaurus. Inland environments also differed, with the contemporary Two Medicine Formation preserving an inland fauna characterized by Maiasaura and the early pachyrhinosaur Einiosaurus.
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Along with the predentary bone, which forms the tip of the lower jaw in all ornithischians, the rostral forms a superficially parrot-like beak. Also, the jugal bones below the eye are prominent, flaring out sideways to make the skull appear somewhat triangular when viewed from above. This triangular appearance is accentuated in later ceratopsians by the rearwards extension of the parietal and squamosal bones of the skull roof, to form the neck frill.You H. & Dodson, P. 2004.
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Ceratopsidae is the most advanced group of Ceratopsians The first ceratopsian remains known to science were discovered during the U.S. Geological and Geographical Survey of the Territories led by the American geologist F.V. Hayden. Teeth discovered during an 1855 expedition to Montana were first assigned to hadrosaurids and included within the genus Trachodon. It was not until the early 20th century that some of these were recognized as ceratopsian teeth.Hatcher, J.B., Marsh, O.C. and Lull, R.S. (1907).
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Since the ceratopsians had not been recognised yet as a distinctive group, Cope was uncertain about much of the fossil material, not recognizing the nasal horn core, nor the brow horns, as part of a fossil horn. The frill bone was interpreted as a part of the breastbone. In 1888 and 1889, Othniel Charles Marsh described the first well preserved horned dinosaurs, Ceratops and Triceratops. In 1890 Marsh classified them together in the family Ceratopsidae and the order Ceratopsia.
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Centrosaurine ceratopsids did not fully develop their cranial ornamentation until fully grown. Scott Sampson argues that comparing ceratopsids to modern mammals with a similar lifecycle can yield insight into the socioecology of the ancient horned dinosaurs. Modern animals with mating signals as prominent as the horns and frills of ceratopsians tend to form these kinds of large, intricate associations. Sampson found in previous work that the centrosaurine ceratopsids did not achieve fully developed mating signals until nearly fully grown.
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Other hypotheses about its function include protection of the neck and anchoring of jaw muscles, but the fragility of the frill and the poor leverage offered by possible attachment sites here makes these ideas implausible. Described by Walter W. Granger and W.K. Gregory in 1923, Protoceratops was initially believed to be an ancestor of the North American ceratopsians. Researchers currently distinguish two species of Protoceratops (P. andrewsi and P. hellenikorhinus), based in part by their respective sizes.
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One individual was found preserved with long filaments on the tail, similar to those of Tianyulong, and scales across the rest of the animal. Psittacosaurus probably had complex behaviours, based on the proportions and relative size of the brain. It may have been active for short periods of time during the day and night, and had well-developed senses of smell and vision. Psittacosaurus was one of the earliest ceratopsians, but closer to Triceratops than Yinlong.
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The late occurrence of pachycephalosaurs compared to the related ceratopsians indicates a long ghost lineage (inferred, but missing from the fossil record) spanning 66 million years, from the Late Jurassic to the Cretaceous. Since pachycephalosaurs were mainly small, this may be due to taphonomic bias; smaller animals are less likely to be preserved through fossilisation. More delicate bones are also less likely to be preserved, which is why pachycephalosaurs are mainly known from their robust skulls.
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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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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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Asiaceratops belonged to the Ceratopsia (the name is Greek for "horned faces"), a group of herbivorous dinosaurs with parrot-like beaks which thrived in North America and Asia during the Cretaceous Period, which ended roughly 66 million years ago. All ceratopsians became extinct at the end of this era. In 1995 Nesov assigned Asiaceratops to an Asiaceratopsinae of its own. Recent cladistic analyses indicated, despite the presumed status as a nomen dubium, a basal position in the Leptoceratopsidae.
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Finally, Horner thought there was a taxon present that was transitional between Daspletosaurus and Tyrannosaurus. In 2017, tyrannosaurid remains from the Two Medicine Formation were named as a new species of Daspletosaurus: Daspletosaurus horneri. The 2017 study considered it plausible that D. horneri was a direct descendant of D. torosus in a process of anagenesis, but rejected the possibility that D. horneri was the ancestor of Tyrannosaurus. Other ceratopsians from the Two Medicine Formation include Einiosaurus and Stellasaurus.
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Skull comparisons of Triceratops and Nedoceratops The type species is Nedoceratops hatcheri. Nedoceratops belonged to the Ceratopsia (the name is Greek for "horned faces", Κερατόψια), a group of herbivorous dinosaurs with parrot-like beaks which thrived in North America and Asia during the Cretaceous Period, which ended roughly 66 million years ago. All ceratopsians became extinct at the end of this era. Several authors have suggested that Nedoceratops may be directly ancestral to Triceratops, or perhaps its nearest relative.
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Also from the section of the formation are the theropods Daspletosaurus, and Saurornitholestes, the hadrosaurids Brachylophosaurus, Gryposaurus and Parasaurolophus, the ankylosaurid Scolosaurus, and the ceratopsians Coronosaurus and Chasmosaurus. Other genera are known, but do not persist from the upper section of the formation, and therefore are not contemporaries of Corythosaurus. Corythosaurus casuarius is widespread throughout the lower unit of the Dinosaur Park Formation. In it, Corythosaurus was found to be closely associated with the ceratopsid Centrosaurus apertus.
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An early ceratopsian: Psittacosaurus Montanoceratops, a leptoceratopsid A typical protoceratopsid: Protoceratops skeleton at the Wyoming Dinosaur Center Styracosaurus, a centrosaurine ceratopsid Triceratops, one of the largest ceratopsians (a chasmosaurinae ceratopsid). It had solid frill and long horns. Following Marsh, Ceratopsia has usually been classified as a suborder within the order Ornithischia. While ranked taxonomy has largely fallen out of favor among dinosaur paleontologists, some researchers have continued to employ such a classification, though sources have differed on what its rank should be.
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Wulatelong shared their habitat in the Bayan Mandahu with a number of other dinosaurian fauna. These included the ceratopsians Protoceratops and Magnirostris, the ankylosaurian Pinacosaurus, and a number of other theropods: the dromaeosaurids Velociraptor and Linheraptor, the oviraptorosaurian Machairasaurus, the alvarezsauroid Linhenykus, and the troodontid Linhevenator. The authors of the paper describing Wulatelong concluded that the Bayan Mandahu fauna "differs fundamentally in composition from the classical Djadokhta fauna, perhaps because of a difference in age" or due to environmental factors.
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Dinosaurs dominate the fauna, especially hadrosaurs, which make up half of all dinosaurs known, including the genera Edmontosaurus, Saurolophus and Hypacrosaurus. Ceratopsians and ornithomimids were also very common, together making up another third of the known fauna. Along with much rarer ankylosaurians and pachycephalosaurs, all of these animals would have been prey for a diverse array of carnivorous theropods, including troodontids, dromaeosaurids, and caenagnathids. Intermingled with the Albertosaurus remains of the Dry Island bonebed, the bones of the small theropod Albertonykus were found.
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Both upper and lower jaws sport a pronounced beak, formed from the rostral and predentary bones, respectively. The bony core of the beak may have been sheathed in keratin to provide a sharp cutting surface for cropping plant material. As the generic name suggests, the short skull and beak superficially resemble those of modern parrots. Psittacosaurus skulls share several adaptations with more derived ceratopsians, such as the unique rostral bone at the tip of the upper jaw, and the flared jugal (cheek) bones.
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The earliest part of this time saw the spread of ankylosaurians, iguanodontians, and brachiosaurids through Europe, North America, and northern Africa. These were later supplemented or replaced in Africa by large spinosaurid and carcharodontosaurid theropods, and rebbachisaurid and titanosaurian sauropods, also found in South America. In Asia, maniraptoran coelurosaurians like dromaeosaurids, troodontids, and oviraptorosaurians became the common theropods, and ankylosaurids and early ceratopsians like Psittacosaurus became important herbivores. Meanwhile, Australia was home to a fauna of basal ankylosaurians, hypsilophodonts, and iguanodontians.
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Udanoceratops, like all ceratopsians, was a herbivore. The short, deep jaws would have given the animal a powerful bite. The toothless beak would have served to grasp and crop stems or leaves, and as in other leptoceratopsids, the teeth would have met with an action that combined shearing and crushing. The feeding adaptations seen in leptoceratopsids suggest a diet of relatively tough food items, however little is known about the plants that grew in the Gobi Desert during the Cretaceous.
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It has been claimed that ceratopsian dinosaurs were herding animals, due to the large number of known bone beds containing multiple members of the same ceratopsian species. In 2010, Hunt and Farke pointed out that this was mainly true for centrosaurine ceratopsians. Horner assumed that the horned dinosaurs at Landslide Butte lived in herds which had been killed by drought or disease. Dodson concluded that the fact that the Achelousaurus bone beds were monospecific (containing only one species) confirmed the existence of herds.
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A bone bed composed of Centrosaurus and Styracosaurus remains is known from the Dinosaur Park Formation in what is now Alberta. The mass deaths may have been caused by otherwise non-herding animals gathering around a waterhole during a drought. Centrosaurus is found lower in the formation than Styracosaurus, indicating that Centrosaurus was displaced by Styracosaurus as the environment changed over time. mega- bonebeds The large frills and nasal horns of the ceratopsians are among the most distinctive facial adornments of all dinosaurs.
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Sharks, rays, sturgeons, bowfins, gars and the gar-like Aspidorhynchus made up the fish fauna. The saltwater plesiosaur Leurospondylus has been found in marine sediments in the Horseshoe Canyon, while freshwater environments were populated by turtles, Champsosaurus, and crocodilians like Leidyosuchus and Stangerochampsa. Dinosaurs dominate the fauna, especially hadrosaurs, which make up half of all dinosaurs known, including the genera Edmontosaurus, Saurolophus and Hypacrosaurus. Ceratopsians and ornithomimids were also very common, together making up another third of the known fauna.
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Artist's restoration of some megafaunal dinosaurs of the Dinosaur Park Formation. The Dinosaur Park Formation is time-equivalent to the Oldman Formation, and both formations are part of the Belly River Group. It represents the deposits of a perennial, sinuous river system and paralic environments. It is widely known for its incredible diversity of dinosaurian fauna, representing over 50 valid taxa including theropods such as dromaeosaurs, caenagnathids, troodontids, ornithomimids, and tyrannosaurids, as well as ornithischians such as pachycephalosaurs, hadrosaurs, ceratopsians, ankylosaurs, and thescelosaurs.
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The "Monoclonius nasicornus" skeleton (material now more usually classified in Centrosaurus or Styracosaurus). In the years after Cope's 1889 paper, it appears that there was a tendency to describe any ceratopsid material from the Judith River beds as Monoclonius. The first dinosaur species described from Canada were ceratopsians, in 1902 by Lawrence Lambe, including three new species of Monoclonius based on fragmentary skulls. Two of these, Monoclonius belli and Monoclonius canadensis, were later seen as two species within separate genera: Chasmosaurus belli and Eoceratops canadensis.
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Another group, Leptoceratopsidae, includes mostly North American animals that are more closely related to Leptoceratops. The third group, Ceratopsoidea, includes the family Ceratopsidae and closely related animals like Zuniceratops. Ceratopsidae itself includes Triceratops and all the large North American ceratopsians and is further divided into the subfamilies Centrosaurinae and Chasmosaurinae. You Hailu of Beijing's Chinese Academy of Geological Sciences, was a co-author with Xu and Makovicky in 2002 but, in 2003, he and Peter Dodson from the University of Pennsylvania published a separate analysis.
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The teeth in the lower jaw may have been 20–30% smaller than those in the upper jaw, but few are known, and they are of uncertain maturity. Apart from this, the teeth were identical. Under each active tooth there was a column of nine replacement teeth within the jaw. With 68 columns in the upper jaws and 60 columns in the lower jaws, these so-called dental batteries (also present in hadrosaurs and ceratopsians) comprised a total of more than 500 active and replacement teeth.
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Although its mass suggests a quadrupedal nature, Massospondylus would have been restricted to its hind legs for locomotion. Since the discovery of rudimentary and nonfunctional clavicles in ceratopsians, it was assumed that these shoulder bones were reduced in all dinosaurs that did not have true furculae. Robert Bakker (1987) suggested that this would have allowed the shoulder blades to swing with the forelimbs in quadrupedal dinosaurs, increasing their functional forelimb length. This would have reduced the discrepancy of length between fore- and hindlimbs in a quadrupedal Massospondylus.
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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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Marginocephalian remains reveal significant evidence of being social creatures, much of which is related to the many possible functions of the bony skull margins. Some possible functions of the variably shaped and sized margins are to ward off predators, display, ritualized combat, defense of territory, or establishing social ordering. Both pachycephalosaurs and ceratopsians show evidence of interspecific communication, and there may be evidence of intraspecific communication. Pachycephalosaurs, with their dome- shaped heads, are commonly thought to have used their thick skulls for butting into each other.
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Hardbound: 634 pp. This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Gryposaurus monumentensis shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaur Parasaurolophus cyrtocristatus, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Other paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians.
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The stegosaurians appear to have gone extinct at some point in the late Early Cretaceous or early Late Cretaceous. A major change in the Early Cretaceous, which would be amplified in the Late Cretaceous, was the evolution of flowering plants. At the same time, several groups of dinosaurian herbivores evolved more sophisticated ways to orally process food. Ceratopsians developed a method of slicing with teeth stacked on each other in batteries, and iguanodontians refined a method of grinding with dental batteries, taken to its extreme in hadrosaurids.
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Turanoceratops belonged to the Ceratopsia (the name is Greek for "horned face"), a group of herbivorous dinosaurs with parrot-like beaks which thrived in North America and Asia during the Cretaceous Period, which ended 66 million years ago. All ceratopsians became extinct at the end of this period. A 2009 study led by Hans-Dieter Sues analysed additional fossil material of Turanoceratops and concluded that, contrary to expectations, it represented a true (though "transitional") member of the family Ceratopsidae. If correct, it would represent an Asian ceratopsid.
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Pentaceratops, like all ceratopsians, was an herbivore. During the Cretaceous, flowering plants were "geographically limited on the landscape" and so it is likely that this dinosaur fed on the predominant plants of the era: ferns, cycads and conifers. It would have used its sharp ceratopsian beak to bite off the branches which were then shredded - leaves, needles and all - by the tooth batteries, providing a self-sharpening continuous cutting edge in both upper and lower jaws. Ultimately the plant material was digested by the large gut.
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"A new species of the centrosaurine ceratopsid Pachyrhinosaurus from the North Slope (Prince Creek Formation: Maastrichtian) of Alaska." Acta Palaeontologica Polonica, available online 26 Aug 2011. Dinosaurs that lived alongside Einiosaurus include the basal ornithopod Orodromeus, hadrosaurids (such as Hypacrosaurus, Maiasaura, and Prosaurolophus), the ankylosaurs Edmontonia and Euoplocephalus, the tyrannosaurid Daspletosaurus (which appears to have been a specialist of preying on ceratopsians), as well as the smaller theropods Bambiraptor, Chirostenotes, Troodon, and Avisaurus. Einiosaurus lived in a climate that was seasonal, warm, and semi-arid.
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Tyrannosaurus and other animals of the Hell Creek Formation Several notable Tyrannosaurus remains have been found in the Hell Creek Formation. During the Maastrichtian this area was subtropical, with a warm and humid climate. The flora consisted mostly of angiosperms, but also included trees like dawn redwood (Metasequoia) and Araucaria. Tyrannosaurus shared this ecosystem with ceratopsians Leptoceratops, Torosaurus, and Triceratops, the hadrosaurid Edmontosaurus annectens, the parksosaurid Thescelosaurus, the ankylosaurs Ankylosaurus and Denversaurus, the pachycephalosaurs Pachycephalosaurus and Sphaerotholus, and the theropods Ornithomimus, Struthiomimus, Acheroraptor, Dakotaraptor, Pectinodon and Anzu.
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Contemporaneous dinosaurs included the microraptorine dromaeosaurid Graciliraptor; the oviraptorosaur Incisivosaurus; the ornithomimosaurs Shenzhousaurus and Hexing; the proceratosaurid tyrannosauroid Dilong; the titanosauriform sauropod Euhelopus; the ornithopod Jeholosaurus; and ceratopsians such as the ubiquitous Psittacosaurus as well as Liaoceratops. Mammals present included Acristatherium, Gobiconodon, Juchilestes, Maotherium, Meemannodon, and Repenomamus. Other tetrapods included the frogs Liaobatrachus and Mesophryne; and the lizard Dalinghosaurus. The Lujiatun Beds consist of fluvial and volcaniclastic deposits, indicating a landscape of rivers bearing volcanoes, which may have killed the preserved animals by lahar.
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The eggs of Citipati are the largest known definitive oviraptorid eggs, at 18 cm. In contrast, eggs associated with Oviraptor are only up to 14 cm long. C. osmolskae egg with preserved embryo Ironically, it was the association with eggs that gave oviraptorids their name (which means 'egg thieves'). The first oviraptorid eggs (of the genus Oviraptor) were found in close proximity to the remains of the ceratopsian dinosaur Protoceratops and it was assumed that the oviraptorids were preying upon the eggs of the ceratopsians.
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Another subset of neoceratopsians is called Coronosauria, which either includes all ceratopsians more derived than Auroraceratops, or more derived than Leptoceratopsidae. Coronosaurs show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head. Within Coronosauria, three groups are generally recognized, although the membership of these groups varies somewhat from study to study and some coronosaurs may not fit in any of them. One group can be called Protoceratopsidae and includes Protoceratops and its closest relatives, all Asian.
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Brenda Chinnery, formerly of the Museum of the Rockies in Bozeman, Montana, independently described Prenoceratops in 2005 and published a new phylogeny. In 2006, Makovicky and Mark Norell of the AMNH incorporated Chinnery's analysis into their own and also added Yamaceratops, although they were not able to include Yinlong. Andrew Farke and his colleagues in 2014 published a description of a new neoceratopsian, Aquilops americanus, through the peer- reviewed science journal PLOS ONE. They analysed their taxa as well as most other primitive ceratopsians to get a consensus cladogram.
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This formation contains one of the best and most continuous records of Late Cretaceous terrestrial life in the world. Parasaurolophus shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, ornithomimids like Ornithomimus velox, tyrannosaurids like Albertosaurus and Teratophoneus, armored ankylosaurids, the duckbilled hadrosaur Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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The Two Medicine Dinosaur Center is a 501(c)(3) non-profit and educational institute located in Bynum, Montana that opened in 1995. It is part of the Montana Dinosaur Trail and home to a skeletal model of what is believed to be the world's largest dinosaur, a seismosaurus. The center also houses the first baby dinosaur bones collected in North America - the original discovery reported by paleontologist John R. Horner. In addition to the above-mentioned displays, the center houses specimens of new species of several types of dinosaurs, including hadrosaurss, ceratopsians, and tyrannosaurs.
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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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Utahceratops shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, tyrannosaurids like Teratophoneus, armored ankylosaurids, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Some fossil evidence suggests the presence of the Tyrannosaurid albertosaurus and the ornithomimid Ornithomimus velox, but the existing assessment of the material is not conclusive. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and hadrosaurine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurine and lambeosaurines dominate in northern latitudes. Holtz has suggested this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and hadrosaurines. At the end of the later Maastrichtian stage, tyrannosaurines like Tyrannosaurus rex, hadrosaurines like Edmontosaurus and chasmosaurines like Triceratops were widespread throughout western North America, while lambeosaurines were rare and albertosaurines and centrosaurines had gone extinct.
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The fact that the holotype was a subadult might have distorted these results because juvenile individuals often show basal traits. However, after correcting for traits that might change during ontogeny, the resulting tree was basically the same. The ceratopsians more derived than psittacosaurids, called neoceratopsians, evolved in Asia: the presence of a basal neoceratopsian in North America was seen as an indication for a late Early Cretaceous migration event, the ancestors of Aquilops invading from Asia. Two later such events would have occurred in the early Late Cretaceous.
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Protoceratops (; from Greek '/ "first", '/ "horn" and '/ "face", meaning "first horned face") is a genus of sheep-sized (1.8 m long) herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period (Campanian stage) of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs. Unlike later ceratopsians, however, it was a much smaller creature that lacked well-developed horns and retained some basal traits not seen in later genera. Protoceratops had a large neck frill which was likely used as a display site to impress other members of the species.
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The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and hadrosaurine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurines and lambeosaurines dominate in northern latitudes. Holtz has suggested that this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and hadrosaurines. At the end of the later Maastrichtian stage, tyrannosaurines like Tyrannosaurus rex, hadrosaurines like Edmontosaurus and chasmosaurines like Triceratops were widespread throughout western North America, while albertosaurines and centrosaurines became extinct, and lambeosaurines were rare.
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The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and hadrosaurine hadrosaurs (a group now generally referred to as saurolophines) are also more common in the Two Medicine Formation and in southwestern North America during the Campanian. Thomas Holtz has suggested that this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and hadrosaurines. Holtz notes that, at the end of the later Maastrichtian stage, tyrannosaurines like Tyrannosaurus rex, hadrosaurines and chasmosaurines like Triceratops were widespread throughout western North America, while albertosaurines and centrosaurines became extinct, and lambeosaurines were very rare.
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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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Sometimes numbering more than fifty, these stones are occasionally found in the abdominal cavities of psittacosaurs, and may have been stored in a gizzard, as in modern birds. Unlike many other dinosaurs, psittacosaurs had akinetic skulls: that is to say, the upper and lower jaws each behaved as a single unit, without internal joints. The only joint was the jaw joint itself, and psittacosaurs could slide their lower jaws forward and backward on the joint, permitting a shearing action. Unlike most ceratopsians, their beaks did not form curved tips, but were instead rounded and flattened.
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Skeletal mount of Titanoceratops This timeline of ceratopsian research is a chronological listing of events in the history of paleontology focused on the ceratopsians, a group of herbivorous marginocephalian dinosaurs that evolved parrot-like beaks, bony frills, and, later, spectacular horns. The first scientifically documented ceratopsian fossils were described by Edward Drinker Cope starting in the 1870s; however, the remains were poorly preserved and their true nature was not recognized. Over the next several decades, Cope named several such genera and species. Cope's hated rival, Othniel Charles Marsh, also described ceratopsian remains.
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Some sauropods also evolved tooth batteries, best exemplified by the rebbachisaurid Nigersaurus. The early forms Herrerasaurus (large), Eoraptor (small) and a Plateosaurus skull There were three general dinosaur faunas in the Late Cretaceous. In the northern continents of North America and Asia, the major theropods were tyrannosaurids and various types of smaller maniraptoran theropods, with a predominantly ornithischian herbivore assemblage of hadrosaurids, ceratopsians, ankylosaurids, and pachycephalosaurians. In the southern continents that had made up the now-splitting Gondwana, abelisaurids were the common theropods, and titanosaurian sauropods the common herbivores.
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Restoration of Rubeosaurus ovatus, the possible adult form Brachyceratops belonged to the Centrosaurinae, but its exact placement has been difficult to discover because it is known only from juvenile specimens. In 1997, Scott Sampson and colleagues re-examined Brachyceratops and noted that it is almost certainly the juvenile form of an already known centrosaurine dinosaur. However, because many features that distinguish ceratopsians from each other do not appear until adulthood, exactly which centrosaurine remained unknown, and Sampson et al. classified Brachyceratops as a nomen dubium, or dubious name.
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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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During this time many new types of dinosaur appeared or came into prominence, including ceratopsians, spinosaurids, carcharodontosaurids and coelurosaurs, while survivors from the Late Jurassic continued to persist. Angiosperms (flowering plants) appeared for the first time during the Early Cretaceous; Archaefructaceae, one of the oldest fossil families (124.6 Ma) was found in the Yixian Formation, China. This time also saw the evolution of the first members of the Neornithes (modern birds). Sinodelphys, a 125 Ma-old boreosphenidan mammal found in the Yixian Formation, China, is one of the oldest mammal fossils found.
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Like other ceratopsids, Coronosaurus had a large frill and horns on its head. These include a small pair of brow horns over its eyes, a large nasal horn on its snout, and, unique among ceratopsians, irregular, spiky bone masses on its frill. Growing up to around long and in weight, it was mid-sized for its kind. The genus is classified as a member of the Centrosaurini, a group of derived centrosaurines which has also been found include taxa such as Styracosaurus, Spinops, Rubeosaurus, and Centrosaurus, the genus it was originally placed within.
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The coprolites also contained traces of mollusc shell, arthropod cuticle, and lizard bone that may have been ingested along with the plant material. They were found near other herbivore coprolites that contained conifer wood. Ridgwell pointed out that the dental anatomies of ceratopsians and hadrosaurs (with dental batteries comprising continuously replaced teeth) were adapted to process large quantities of fibrous plants. The different diets represented by the coprolites may indicate niche partitioning among the herbivores of the Kaiparowits Formation ecosystem, or that there was seasonal variation in diet.
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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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Many dinosaur species in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. Large herbivores like ceratopsians and hadrosaurs exhibited the most obvious endemism, which strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent." Lehman observes that "it is often the most conspicuous and abundant species with the most restricted distributions." He notes that Corythosaurus and Centrosaurus haven't been discovered outside of southern Alberta even though they are the most abundant Judithian dinosaurs in the region.
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Thomas M. Lehman has observed that Corythosaurus and Centrosaurus haven't been discovered outside of southern Alberta even though they are the most abundant Judithian dinosaurs in the region. Large herbivores like the ceratopsians and hadrosaurs living in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent." Another example is Pentaceratops, the only known Judithian ceratopsian from New Mexico.
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Ornithopoda Studies of sexual dimorphism in hadrosaurs have generally centered on the distinctive cranial crests, which likely provided a function in sexual display. A biometric study of 36 skulls found sexual dimorphism was exhibited in the crest of 3 species of hadrosaurids. The crests could be categorized as full (male) or narrow (female) and may have given some advantage in intrasexual mating-competition. Ceratopsians According to Scott D. Sampson, if ceratopsids were to exhibit sexual dimorphism, modern ecological analogues suggest it would be found in display structures, such as horns and frills.
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Akainacephalus shared its paleoenvironment with other dinosaurs, such as dromaeosaurid theropods, the troodontid Talos sampsoni, tyrannosaurids like Teratophoneus, the duckbilled hadrosaurs Parasaurolophus cyrtocristatus and Gryposaurus monumentensis, the ceratopsians Utahceratops gettyi, Nasutoceratops titusi and Kosmoceratops richardsoni and the oviraptorosaurian Hagryphus giganteus. Some fossil evidence suggests the presence of the tyrannosaurid Albertosaurus and the ornithomimid Ornithomimus velox, but the existing assessment of the material is not conclusive. Paleofauna present in the Kaiparowits Formation included chondrichthyans (sharks and rays), frogs, salamanders, turtles, lizards and crocodilians. A variety of early mammals were present including multituberculates, marsupials, and insectivorans.
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Early members of the ceratopsian group, such as Psittacosaurus, were small bipedal animals. Later members, including ceratopsids like Centrosaurus and Triceratops, became very large quadrupeds and developed elaborate facial horns and frills extending over the neck. While these frills might have served to protect the vulnerable neck from predators, they may also have been used for display, thermoregulation, the attachment of large neck and chewing muscles or some combination of the above. Ceratopsians ranged in size from 1 meter (3 ft) and 23 kilograms (50 lb) to over 9 meters (30 ft) and 9,100 kg (20,100 lb).
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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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Modern animals with mating signals as prominent as the horns and frills of ceratopsians tend to form these kinds of large, intricate associations. Sampson found in previous work that the centrosaurine ceratopsids did not achieve fully developed mating signals until nearly fully grown. He finds commonality between the slow growth of mating signals in centrosaurines and the extended adolescence of animals whose social structures are ranked hierarchies founded on age-related differences. In these sorts of groups young males are typically sexually mature for several years before actually beginning to breed, when their mating signals are most fully developed.
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Both Abrictosaurus and Heterodontosaurus had very large eyes. Underneath the eyes, the jugal bone projected sideways, a feature also present in ceratopsians. As in the jaws of most ornithischians, the anterior edge of the premaxilla (a bone at the tip of the upper jaw) was toothless and probably supported a keratinous beak (rhamphotheca), although heterodontosaurids did have teeth in the posterior section of the premaxilla. A large gap, called a diastema, separated these premaxillary teeth from those of the maxilla (the main upper jaw bone) in many ornithischians, but this diastema was characteristically arched in heterodontosaurids.
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P. lujiatunensis skull LHPV 1 from the left and above The brain of P. lujiatunensis is well known; a study on the anatomy and functionality of three specimens was published in 2007. Until the study, it was generally thought the brain of Psittacosaurus would have been similar to other ceratopsians with low Encephalisation Quotients. Russell and Zhao (1996) believed "the small brain size of psittacosaurs implies a very restrictive behavioural repertoire relative to that of modern mammals of similar body size". However, the 2007 study dispelled this theory when it found the brain to be more advanced.
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The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and saurolophine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurines and lambeosaurines dominate in northern latitudes. Holtz has suggested this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and saurolophines. At the end of the later Maastrichtian stage, tyrannosaurines like Tyrannosaurus rex, saurolophines like Edmontosaurus and Kritosaurus and chasmosaurines like Triceratops and Torosaurus were widespread throughout western North America, while lambeosaurines were rare, consisting of a few species like Hypacrosaurus, and albertosaurines and centrosaurines had gone extinct.
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The first specimen discovered was a single exceptionally well-preserved skeleton, complete with skull, of a nearly adult animal, found in 2004 in the Middle-Late Jurassic strata of the Shishugou Formation located in Xinjiang Province, China. Yinlong was discovered in an upper section of this formation which dates to the Oxfordian stage of the Late Jurassic, or 161.2 to 155.7 million years ago.Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix. All other described ceratopsians are known from the later Cretaceous Period.
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In the first attempt to understand the many species, Lull found two groups, although he did not say how he distinguished them: one composed of T. horridus, T. prorsus, and T. brevicornus; the other of T. elatus and T. calicornis. Two species (T. serratus and T. flabellatus) stood apart from these groups. By 1933, and his revision of the landmark 1907 Hatcher-Marsh-Lull monograph of all known ceratopsians, he retained his two groups and two unaffiliated species, with a third lineage of T. obtusus and T. hatcheri that was characterized by a very small nasal horn.
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Zuniceratops, the earliest-known ceratopsian with brow horns, was described in the late 1990s, and Yinlong, the first known Jurassic ceratopsian, in 2005. These new finds have been vital in illustrating the origins of horned dinosaurs in general, suggesting an Asian origin in the Jurassic, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America. In phylogenetic taxonomy, the genus Triceratops has been used as a reference point in the definition of Dinosauria; dinosaurs have been designated as all descendants of the most recent common ancestor of Triceratops and Neornithes (i.e. modern birds).
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Also with this publication are two other papers, one describing the site taphonomy and quarry map and another paper describing the endocast and brain structure of P. lakustai. Tanke has also authored papers on Tyrannosaurus, Daspletosaurus, Styracosaurus, Chasmosaurus, Stegoceras, Centrosaurus, Eoceratops, and various other hadrosaurids, ceratopsians, and tyrannosaurids. Tanke is presently the longest serving employee (36+ years) with the Royal Tyrrell Museum. On August 7, 2008 at the 33rd International Geological Congress meetings in Oslo, Norway, he was made a member of INHIGEO (International Commission on the History of Geological Sciences) and is now the Canadian editor for that organization.
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Restoration Anchiceratops is rare compared to other ceratopsians in the area, and usually found near marine sediments, in both the Horseshoe Canyon and Dinosaur Park Formations. This indicates that Anchiceratops may have lived in estuaries where other ceratopsids did not live. Flowering plants were increasingly common but still rare compared to the conifers, cycads and ferns which probably made up the majority of ceratopsian diets. In 1914 Brown suggested that the distinctive frill and horn form of Anchiceratops were caused by sexual selection and intra-species recognition, as he could not explain the differences between the taxa by a difference in defence function.
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Anchiceratops specimens are found in the upper part of Unit one of this formation, part of the Horsetheif member, dated to about 72-71 million years ago. Anchiceratops shared its paleoenvironment with other dinosaurs, such as maniraptorans (Epichirostenotes curriei), ornithomimids (Ornithomimus edmontonicus), pachycephalosaurids (Sphaerotholus edmontonensis), hadrosaurids (Edmontosaurus regalis), ceratopsians (Pachyrhinosaurus canadensis), and unidentified tyrannosaurids, which were apex predators. Of these, the hadrosaurs dominated in terms of sheer number and made up half of all dinosaurs who lived in this region. Other vertebrates present in the Horseshoe Canyon Formation at the time of Anchiceratops included reptiles, and amphibians.
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The formation has a diverse assemblage of dinosaurs including theropods such as Troodon, Albertosaurus, ornithomimids and dromaeosaurs, as well as several types of hadrosaurs, ceratopsians, ankylosaurs, and smaller ornithischians such as Orodromeus. It also includes pterodactyloid pterosaurs, Champsosaurus, turtles, lizards, and mammals. Other types of eggs from Two Medicine include Montanoolithus, Prismatoolithus levis (the eggs of Troodon formosus), some small unidentified theropod eggs, P. hirschi, Triprismatoolithus, Tubercuoolithus, Spheroolithus albertensis (eggs of Maiasaura), S. choteauensis, eggs of Hypacrosaurus, and Krokolithes. The Oldman Formation was formed by ephemeral rivers in a semi- arid environment characterized by seasonal precipitation.
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However, a recent discovery shows that Massospondylus possessed well-developed clavicles that were joined in a furcula-like arrangement, acting like a clasp between the right and left shoulder blades and prohibiting any rotation of these bones. This discovery indicates that the clavicle reduction is limited to the evolutionary line leading to the ceratopsians. It also indicates that the furcula of birds is derived from clavicles. Michael Cooper (1981) noted that the zygapophyses of the neck vertebrae were inclined, prohibiting significant horizontal movement of the neck, so that "consequently any significant movement in this direction must have been accomplished by a change in the position of the entire body".
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In 1970, Dale Russell hypothesized that the more common Gorgosaurus actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavily built Daspletosaurus. However, a specimen of Daspletosaurus (OTM 200) from the contemporaneous Two Medicine Formation of Montana preserves the digested remains of a juvenile hadrosaur in its gut region. Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other. However, Gorgosaurus appears more common in northern formations like the Dinosaur Park, with species of Daspletosaurus more abundant to the south.
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The Judith River Group preserves the remains of many aquatic amphibians and reptiles, including frogs, salamanders, turtles, Champsosaurus and crocodilians. Terrestrial lizards, including whiptails, skinks, monitors and alligator lizards have also been discovered. Azhdarchid pterosaurs, and birds like Apatornis and Avisaurus flew overhead, while several varieties of mammals coexisted with Daspletosaurus and other types of dinosaurs in the various formations that make up the Judith River wedge. Skull of a juvenile D. horneri In the Oldman Formation (the geological equivalent of the Judith River formation), Daspletosaurus torosus could have preyed upon the hadrosaur species Brachylophosaurus canadensis, the ceratopsians Coronosaurus brinkmani and Albertaceratops nesmoi, pachycephalosaurs, ornithomimids, therizinosaurs and possibly ankylosaurs.
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The sclerotic rings in reptiles directly show the size of the eyeball. The rings are not well preserved in Psittacosaurus, with one individual preserving them likely contracted postmortem, but if they are similar to those of Protoceratops, Psittacosaurus would have had large eyes and acute vision. The curvature of the semicircular canals is related to the agility of reptiles, and the large curved canals in Psittacosaurus show that the genus was much more agile than later ceratopsians. Comparisons between the scleral rings of Psittacosaurus and modern birds and reptiles suggest that it may have been cathemeral, active throughout the day and for short intervals at night.
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Lambe was sympathetic to this idea of a new type of "unicorn dinosaur" in a 1903 review of Nopscsa's paper. At this time, there was still uncertainty over which group of dinosaur Stegoceras belonged to, with both ceratopsians (horned dinosaurs) and stegosaurs (plated dinosaurs) as contenders. Hatcher doubted whether the Stegoceras specimens belonged to the same species and whether they were dinosaurs at all, and suggested the domes consisted of the frontal, occipital, and parietal bones of the skull. In 1918, Lambe referred another dome (CMN 138) to S. validus, and named a new species, S. brevis, based on specimen CMN 1423 (which he originally included in S. validus).
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Ischioceratops is an extinct genus of small ceratopsian dinosaur that lived approximately 69 million years ago during the latter part of the Cretaceous Period in what is now China. Ischioceratops was a small sized, moderately- built, ground-dwelling, quadrupedal herbivore, whose total body length has been estimated to be about 2 meters. The ceratopsians were a group of dinosaurs with parrot-like beaks which fed on vegetation and thrived in North America and Asia during the Cretaceous Period, which ended approximately 66 million years ago, at which point they all became extinct. Its name means "ischium horned face", referring to the peculiar shape of the ischiatic bones.
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Comparisons between the scleral rings of dinosaurs and modern birds and reptiles have been used to infer daily activity patterns of dinosaurs. Although it has been suggested that most dinosaurs were active during the day, these comparisons have shown that small predatory dinosaurs such as dromaeosaurids, Juravenator, and Megapnosaurus were likely nocturnal. Large and medium-sized herbivorous and omnivorous dinosaurs such as ceratopsians, sauropodomorphs, hadrosaurids, ornithomimosaurs may have been cathemeral, active during short intervals throughout the day, although the small ornithischian Agilisaurus was inferred to be diurnal. Based on current fossil evidence from dinosaurs such as Oryctodromeus, some ornithischian species seem to have led a partially fossorial (burrowing) lifestyle.
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Skin impression of AMNH 5427 Thomas M. Lehman has observed that Centrosaurus fossils haven't been found outside of southern Alberta even though they are among the most abundant Judithian dinosaurs in the region. Large herbivores like the ceratopsians living in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent."Lehman, T. M., 2001, Late Cretaceous dinosaur provinciality: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 310-328.
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The most complete specimen measures up to in length though T. rex could grow to lengths of over , up to tall at the hips, and according to most modern estimates to in weight. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it is still among the largest known land predators and is estimated to have exerted the strongest bite force among all terrestrial animals. By far the largest carnivore in its environment, Tyrannosaurus rex was most likely an apex predator, preying upon hadrosaurs, armored herbivores like ceratopsians and ankylosaurs, and possibly sauropods. Some experts have suggested the dinosaur was primarily a scavenger.
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Theropods include the tyrannosaurid Teratophoneus, the oviraptorosaur Hagryphus, an unnamed ornithomimid, the troodontid Talos, indeterminate dromaeosaurids, and the bird Avisaurus. Other vertebrates include crocodiles (such as Deinosuchus and Brachychampsa), turtles (such as Adocus and Basilemys), pterosaurs, lizards, snakes, amphibians, mammals, and fishes. The two most common groups of large vertebrates in the formation are hadrosaurs and ceratopsians (the latter representing about 14 percent of associated vertebrate fossils), which may either indicate their abundance in the Kaiparowits fauna or reflect preservation bias (a type of sampling bias) due to these groups also having the most robust skeletal elements. Eggs from dinosaurs, crocodiles, and turtles have also been found.
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The portion of the head that is preserved shows remarkable similarities to the specialized heads of pachycephalosaurs. Five bosses, or rounded protuberances of bone are visible on the fossil, with one on the frontal bone and two pairs behind (respectively on the postorbital bone and the squamosal/parietal bones) separated by a shallow groove. The backmost pair of bosses form a thick shelf that stretches outwards and backwards over the rear end of the skull, comparable to the domes of pachycephalosaurs and the frills of ceratopsians. The bosses have very roughly textured surfaces, suggesting that they would have been covered by keratin in life.
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Protoceratopsids may have had cheeks to hold food in their mouths. They have very well-defined maxillary and dentary ridges where the muscles in the cheek would have connected, and a number of foramina dotted the maxilla which allowed branches from the trigimenal nerve to reach the tissues attached to the maxilla, indicating that such tissues were likely muscular. The end of the upper jaw was likely not fleshy but instead covered by a horn-like material, and the upper and lower jaws curved in towards each other. Compared to more derived ceratopsians, protoceratopsids had a deep and wide oral cavity, though more narrow than in predecessors like Psittacosaurus, which may have aided in breathing or thermoregulation.
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The hadrosaurs and ceratopsians of the Cretaceous Period, as well as many herbivorous mammals, would convergently evolve somewhat analogous dental batteries. As opposed to hadrosaurs, which had hundreds of teeth constantly being replaced, tooth replacement in heterodontosaurids occurred far more slowly and several specimens have been found without a single replacement tooth in waiting. Characteristically, heterodontosaurids lacked the small openings (foramina) on the inside of the jaw bones which are thought to have aided in tooth development in most other ornithischians. Heterodontosaurids also boasted a unique spheroidal joint between the dentaries and the predentary, allowing the lower jaws to rotate outwards as the mouth was closed, grinding the cheek teeth against each other.
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Histological examination reveals that the frill of Triceratops is composed of fibrolamellar bone which contains fibroblasts that play a critical role in wound healing, and are capable of rapidly depositing bone during remodeling. Juvenile and adult skulls—the juvenile skull is about the size of an adult human head One skull was found with a hole in the jugal bone, apparently a puncture wound sustained while the animal was alive, as indicated by signs of healing. The hole has a diameter close to that of the distal end of a Triceratops horn. This, and other apparent healed wounds in the skulls of ceratopsians, has been cited as evidence of non-fatal intraspecific competition in these dinosaurs.
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Leg bones of Eolambia – femur (A-F), tibia (G-L), fibula (M-N) Kirkland, Cifelli, and colleagues noted that the fauna of the Mussentuchit – iguanodonts, pachycephalosaurs, and ceratopsians – bears strong similarities to contemporary Asian faunas. They proposed that Eolambia was part of an influx of Asian dinosaurs into North America during the Cenomanian, which supplanted the earlier low-diversity native fauna. This hypothesis is supported by the close relationship between Eolambia and either Probactrosaurus or Fukuisaurus, which have respectively been recovered by the phylogenies of Head and Sues & Averianov. However, the results of Horner and colleagues, Prieto-Márquez, and McDonald and colleagues, which consider the North American Protohadros to be the closest relative of Eolambia, contradict this hypothesis.
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As a sub-adult its postorbital horncores are pyramidal in shape with a slight lateral inflection of the distal, upper, one half. Uniquely among ceratopsians, Coronosaurus possesses a number of accessory epiparietal ossifications rear parietal frill of the skull that fuse to the posterior and dorsal frill surface. They develop through ontogeny, the growth of the individual, as short spines that may fuse along their adjacent margins into larger, irregular bone masses. They are located close to the midline of the frill in a closely packed bunch above the base of the first epiparietal (P1), the bone spur that at each side growths downwards over the large opening in each frill half.
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No convincing evidence for sexual dimorphism in body size or mating signals is known in ceratopsids, although there is evidence that the more primitive ceratopsian Protoceratops andrewsi possessed sexes that were distinguishable based on frill and nasal prominence size. This is consistent with other known tetrapod groups where midsized animals tend to exhibit markedly more sexual dimorphism than larger ones. However, it has been proposed that these differences can be better explained by intraspecific and ontogenic variation rather than sexual dimorphism. In addition, many sexually dimorphic traits that may have existed in ceratopsians include soft tissue variations such as coloration or dewlaps, which would be unlikely to have been preserved in the fossil record.
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Marcel Delgado: The Man Who Made Monsters Retrieved October 1, 2009. Because Knight worked in an era when new and often fragmentary fossils were coming out of the American west in quantity, not all of his creations were based on solid evidence; dinosaurs such as his improbably-adorned Agathaumas (1897) for example, were somewhat speculative. His depictions of better-known ceratopsians as solitary animals inhabiting lush grassy landscapes were largely imaginative (the grasslands that feature in many of his paintings didn't appear until the Cenozoic). Although Knight sometimes made musculoskeletal studies of living animals, he did not do so for his dinosaur restorations, and he restored many dinosaurs with typical reptilian-like limbs and narrow hips (Paul, 1996).
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The Hilda mega-bonebed may also support the previously suggested notion that some kinds of centrosaurines participated in seasonal migrations, travelling from east to west. Brinkman and others proposed this hypothesis in 1998 to explain why ceratopsians represented a greater portion of ornithischian biodiversity at sites like Unity, Saskatchewan or Onefour, Alberta near the ancient coast, while the famous centrosaur bonebeds of Dinosaur Provincial Park were all preserved in more inland habitats. The migration hypothesis proposed by Brinkman and the others was that centrosaurs bred near the coast and reared their young in small family groups. These groups would then migrate toward the west in order to avoid seasonal hazards like storms or to exploit seasonally available resources in that direction.
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The age Titanoceratops lived in is called the Kirtlandian land-vertebrate age, and it is characterized by the appearance of Pentaceratops sternbergii. A moderately diverse fauna is known from the Kirtland and Fruitland formations. Among the dinosaurs known from the Fruitland and Kirtland formations are the theropods Bistahieversor sealeyi (previously Daspletosaurus and Albertosaurus sp.), "Saurornitholestes" robustus, Paronychodon lacustris, and an indeterminate ornithomimid (previously Ornithomimus antiquus); the hadrosaurids Anasazisaurus horneri and Parasaurolophus cyrtocristatus; the pachycephalosaur Stegoceras novomexicanum (previously S. validum); the ankylosaur Nodocephalosaurus kirtlandensis; and the ceratopsians Pentaceratops sternbergii and an unidentified centrosaurine. Non-dinosaurian fauna include the fishes Myledaphus bypartitus, and Melvius chauliodous; the turtles Denazinemys ornata, Denazinemys nodosa, Boremys grandis, Neurankylus baeuri, Adocus bossi, Adocus kirtlandicus, Basilemys nobilis, Asperideretes ovatus, "Plastomenus" robustus, and Bothremydidae n. gen.
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In 1970, Dale Russell hypothesized the more common Gorgosaurus actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavy built Daspletosaurus. However, a specimen of Daspletosaurus (OTM 200) from the contemporaneous Two Medicine Formation of Montana preserves the digested remains of a juvenile hadrosaur in its gut region, and another bonebed contains the remains of three Daspletosaurus along with the remains of at least five hadrosaurs. Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other. However, Gorgosaurus appears more common in northern formations like Dinosaur Park, with species of Daspletosaurus more abundant to the south.
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From the fifth came the stars, planets and moons, and from the sixth came all the plants. Finally, from the seventh came all the herbivores (Ceratopsians, Ankylosaurs, Sauropods and Hadrosaurs, among others), and from the eighth and final egg came the carnivores which preyed upon them, (Tyrannosaurs, Ornithomimids and Dromaeosaurids, among others.) God created the five original female hunters by biting off her left arm, each of her fingers becoming a Quintaglio. They wished to create as God did, so she bit off her right arm and these became the first males, the mates of the original hunters. Quintaglio tradition states that a Quintaglio must go on at least one proper hunt in their life in order to go through the rites of passage.
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In 1970, Dale Russell hypothesized that the more common Gorgosaurus actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome ceratopsians and ankylosaurians (horned and heavily armoured dinosaurs) were left to the more heavy built Daspletosaurus. However, a specimen of Daspletosaurus (OTM 200) from the contemporaneous Two Medicine Formation of Montana preserves the digested remains of a juvenile hadrosaur in its gut region, and another bonebed contains the remains of three Daspletosaurus along with the remains of at least five hadrosaurs. Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other. However, Gorgosaurus appears more common in northern formations like Dinosaur Park, with species of Daspletosaurus being more abundant to the south.
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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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Low-diversity and single-species bonebeds are thought to represent herds that may have died in catastrophic events, such as during a drought or flood. This is evidence that Einiosaurus, as well as other centrosaurine ceratopsians such as Pachyrhinosaurus and Centrosaurus, were herding animals similar in behavior to modern-day bison or wildebeest. In contrast, ceratopsine ceratopsids, such as Triceratops and Torosaurus, are typically found singly, implying that they may have been somewhat solitary in life, though fossilized footprints may provide evidence to the contrary. In 2010, a study by Julie Reizner of the individuals excavated at the Dino Ridge site concluded that Einiosaurus grew quickly until its third to fifth year of life after which growth slowed, probably at the onset of sexual maturity.
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Bakker and Galton recognised Heterodontosaurus as important to the evolution of ornithischian dinosaurs, as its hand pattern was shared with primitive saurischians, and therefore was primitive or basal to both groups. This was disputed by some scientists who believed the two groups had instead evolved independently from "thecodontian" archosaur ancestors, and that their similarities were due to convergent evolution. Some authors also suggested a relationship, such as descendant/ancestor, between heterodontosaurids and fabrosaurids, both being primitive ornithischians, as well as to primitive ceratopsians, such as Psittacosaurus, though the nature of these relations was debated. By the 1980s, most researchers considered the heterodontosaurids as a distinct family of primitive ornithischian dinosaurs, but with an uncertain position with respect to other groups within the order.
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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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Star Fox Adventures features both the established main characters of the Star Fox series—Fox, Falco Lombardi, Slippy Toad and Peppy Hare (though Falco is absent for the majority of the game), as well as a host of new characters, including a mysterious blue fox named Krystal and the small dinosaur Prince Tricky. The entire planet is populated with dinosaurs, like the tyrannical General Scales, and other prehistoric animals such as pterosaurs and mammoths. The entire game takes place on the world of Dinosaur Planet (known as "Sauria" in subsequent games) and a number of detached pieces of the planet that are suspended in orbit around it. Dinosaur Planet is ruled by the EarthWalker tribe, resembling ceratopsians, and the rival CloudRunner tribe, similar to pterosaurs and birds.
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Cranial remains Mosaiceratops lived in the upper Cretaceous in what is now the Henan Province of China. The holotype is represented by an incomplete and disarticulated skeleton including pelvis bones and leg bones (femur, tibia, fibula, ischium, ilium, some phalanges and metatarsals, calcaneum and astragalus), 24 vertebrae (3 cervicals, 3 dorsals and 18 caudals), a dorsal rib, a humerus, a radius and the anterior part of an articulated skull with a disarticulated postorbital bone and squamosal. The articulates skull preserves the rostral bone, premaxilla, maxilla, jugal bone, quadratojugal, dentary, surangular, angular bone, the anterior section of the prefrontal bone, and the anterior part of the nasal bone. The name Mosaiceratops means "mosaic horned face", which refers to the mosaic of features normally found on basal neoceratopsians, psittacosaurids and other basal ceratopsians.
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Just like the Claosaurus specimen, it is possible that the specimens of Niobrarasaurus, Silvisaurus and Hierosaurus floated into the Interior Seaway from the east, since these two species of nodosaurids were discovered in the famous chalk formations of Kansas and are not known from any location from Western North America. Kansas was also a part of Appalachia when the other parts were covered by oceans, which were a part of the Western Interior Seaway. While remains of the advanced ceratopsians, most notably the centrosaurines and chasmosaurines which were very common in Laramidia during this time period, where not found in Appalachia, the leptoceratopsids somehow managed to inhabit that location. A Campanian-era leptoceratopsid ceratopsian has been found in the Tar Heel Formation, marking the first discovery of a ceratopsian dinosaur in the Appalachian zone.
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In the prehistoric eras, the species Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly juvenile sauropods, although some experts have suggested the dinosaur was primarily a scavenger. The debate about whether Tyrannosaurus was an apex predator or scavenger was among the longest ongoing feuds in paleontology; however, most scientists now agree that Tyrannosaurus was an opportunistic carnivore, acting mostly as a predator but scavenging when it could. Recent research also shows that while an adult Tyrannosaurus rex would energetically gain little though scavenging, smaller theropods of approximately may have potentially gained levels similar to that of hyenas, though not enough for them to rely on scavenging. There are also an info that Otodus megalodon, Ceratosaurus, Andrewsarchus and some more prehistoric animals were scavengers.
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Since the 1930s, Barnum Brown described that an unsubscribed species of Kritosaurus, the most likely candidate being Kritosaurus navajovius, had inhabited the late Maastrichtian Ojo Alamo Formation, the Javelina Formation in Texas and the El Picacho Formation, which was a flood plain type environment at the time of the Cretaceous. These fossils might be of an unknown species of hadrosaur or an undescribed specimen of Kritosaurus. This genus lived alongside numerous species of dinosaurs including the sauropod Alamosaurus, the ceratopsians Bravoceratops, Ojoceratops, Torosaurus and a possible species of Eotriceratops, hadrosaurs which included a possible species of Edmontosaurus annectens, Saurolophus and Gryposaurus and the armored nodosaur Glyptodontopelta. Theropods from this environment which included Tyrannosaurus, smaller theropods like a species of Troodon and Richardoestesia, the oviraptorid Ojoraptorsaurus, indeterminate ornithomimids and dromaeosaurs.
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North American herbivorous dinosaurs from this time period include the titanosaur sauropod Alamosaurus, the ceratopsians Bravoceratops, Regaliceratops, Triceratops, Leptoceratops, Torosaurus, Nedoceratops, Tatankaceratops (the latter two possible species of Triceratops), and Ojoceratops, the pachycephalosaurs Pachycephalosaurus, Stygimoloch, Dracorex, and Sphaerotholus, the hadrosaurs Augustynolophus, Saurolophus and Edmontosaurus, the ornithopod Thescelosaurus the ankylosaur Ankylosaurus and the nodosaurs Denversaurus, Glyptodontopelta and Edmontonia. Predatory dinosaurs from this time period included the tyrannosaurids Tyrannosaurus, Nanotyrannus (which may just be a juvenile of the former) and Dryptosaurus, the ornithomimids Ornithomimus, Dromiceiomimus, Struthiomimus, the oviraptorids Anzu, Leptorhynchos and Ojoraptorsaurus, the troodontids Pectinodon, Paronychodon and Troodon, the coelurosaur Richardoestesia and the dromaeosaurs Acheroraptor and Dakotaraptor. The only dinosaur fossil from Central America currently is a femur of an ornithopod.,LUCAS, S. G., 2014: Vertebrate paleontology in Central America: 30 years of progress.
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He has also conducted research on dinosaur material from Mongolia and tetrapod-bearing deposits in Sudan. Evans has also been involved with both fieldwork and research of the Early Jurassic sauropodomorph Massospondylus from South Africa and has conducted research on pelycosaurian-grade Permian synapsids, Permian temnospondyls, the iconic Pleistocene felid Smilodon, and choristoderes. Evans has been a part of various teams that have named over a dozen new genera or species of dinosaurs. New ceratopsians named by Evans and colleagues include Xenoceratops foremostensis Ryan, Evans, & Shepherd, 2012; Gryphoceratops morrisoni Ryan, Evans, Currie, Brown, & Brinkman, 2012; Unescoceratops koppelhusi Ryan, Evans, Currie, Brown, & Brinkman, 2012; Mercuriceratops gemini Ryan, Evans, Loewen, & Currie, 2014; Wendiceratops pinhorensis Evans & Ryan, 2015; Spiclypeus shipporum Mallon, Ott, Larson, Iuliano, & Evans, 2016; and Ferrisaurus sustutensis Arbour & Evans, 2019.
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C.W. Gilmore, 1917, "Brachyceratops, a ceratopsian dinosaur from the Two Medicine Formation of Montana, with notes on associated fossil reptiles", United States Geological Survey Professional Paper 103: 1-45 In 1939 Gilmore referred a larger subadult specimen, USNM 14765, to Brachyceratops.Gilmore C.W. 1939, "Ceratopsian dinosaurs from the Two Medicine Formation, Upper Cretaceous of Montana", Proceedings of the United States National Museum 87: 1–18 All specimens are currently part of the collection of the Smithsonian Institution in Washington D.C., where a skeletal restoration is mounted. As Brachyceratops is known only from the remains of five juveniles — plus the subadult that Gilmore found about a mile from the original specimens —, it was long considered likely that these represented the immature forms of known centrosaurine ceratopsians, with Monoclonius often suggested as the likeliest candidate.
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Unlike sharks however, who lose all of their old teeth, teeth in the rapidly growing dental battery would wear completely down and be reabsorbed by the renewing structure around it. The batteries were formed by the teeth growing fast and maturing early, to the point that the pulp cavity of individual teeth—usually filled with cells and connective tissue—were totally filled with dentine before it even erupted. The lack of pulp in the tooth post-eruption means that the tooth was essentially dead and able to be completely worn away through use, and replaced without the risk of exposing the normally sensitive dental pulp to infection and pain. While other dinosaurs, such as some ceratopsians and sauropods, also possessed dental batteries, they all evolved independently and differ in some form or function from those of hadrosaurs.
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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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A herd of P. perotorum resting next to contemporaneous paleofauna from the Prince Creek Formation Pachyrhinosaurus shared its paleoenvironment with other dinosaurs, such as the ceratopsians Anchiceratops and Montanoceratops cerorhynchus, the armored nodosaur Edmontonia longiceps, the duckbilled hadrosaur Edmontosaurus regalis, the theropods Saurornitholestes and Troodon, possibly the ornithopod Thescelosaurus, and the tyrannosaurid Albertosaurus, which was likely the apex predator in its ecosystem. Vertebrates present in the St. Mary River Formation at the time of Pachyrhinosaurus included the actinopterygian fishes Amia fragosa, Lepisosteus, Belonostomus, Paralbula casei, and Platacodon nanus, the mosasaur Plioplatecarpus, the turtle Boremys and the diapsid reptile Champsosaurus. A fair number of mammals lived in this region, which included Turgidodon russelli, Cimolestes, Didelphodon, Leptalestes, Cimolodon nitidus, and Paracimexomys propriscus. Non-vertebrates in this ecosystem included mollusks, the oyster Crassostrea wyomingensis, the small clam Anomia, and the snail Melania.
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Pie chart of the time averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area In its southern range Tyrannosaurus lived alongside the titanosaur Alamosaurus, the ceratopsians Torosaurus, Bravoceratops and Ojoceratops, hadrosaurs which consisted of a species of Edmontosaurus, Kritosaurus and a possible species of Gryposaurus, the nodosaur Glyptodontopelta, the oviraptorid Ojoraptosaurus, possible species of the theropods Troodon and Richardoestesia, and the pterosaur Quetzalcoatlus. The region is thought to have been dominated by semi-arid inland plains, following the probable retreat of the Western Interior Seaway as global sea levels fell. Tyrannosaurus may have also inhabited Mexico's Lomas Coloradas formation in Sonora. Though skeletal evidence is lacking, six shed and broken teeth from the fossil bed have been thoroughly compared with other theropod genera and appear to be identical to those of Tyrannosaurus.
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Christopher J. Ott and Peter L. Larson, 2010, "A New, Small Ceratopsian Dinosaur from the Latest Cretaceous Hell Creek Formation, Northwest South Dakota, United States: A Preliminary Description", In: Ryan, M.J., Chinnery-Allgeier, B.J., and Eberth, D.A. (eds.) New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium, Bloomington, Indiana University Press, 656 pp. Tatankaceratops is known from one specimen housed at the Black Hills Institute, BHI 6226. In 2011, Nick Longrich published a paper containing a brief re-evaluation of Tatankaceratops. Longrich suggested that Tatankaceratops appeared to possess a bizarre mix of characteristics from adult and juvenile Triceratops specimens; the animal's small size and short, slender brow horns are consistent with the animal being a juvenile, but the gnarled bone and fusion of skull elements to one another are typical of old adult ceratopsians.
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Restoration of P. lakustai P. canadensis coexisted with ankylosaurids Anodontosaurus lambei and Edmontonia longiceps, the maniraptorans Atrociraptor marshalli, Epichirostenotes curriei, the troodontid Albertavenator curriei, the alvarezsaurid theropod Albertonykus borealis, the ornithomimids Dromiceiomimus brevitertius, Ornithomimus edmontonicus, and an unnamed species of Struthiomimus, the bone-head pachycephalosaurids Stegoceras, and Sphaerotholus edmontonensis, the ornithopod Parksosaurus warreni, the hadrosaurids Edmontosaurus regalis, Hypacrosaurus altispinus, and Saurolophus osborni, the ceratopsians Anchiceratops ornatus, Arrhinoceratops brachyops, Eotriceratops xerinsularis, Montanoceratops cerorhynchus, and the tyrannosaurids Albertosaurus sarcophagus and a possible species of Daspletosaurus, which were the apex predators of this paleoenvironment. Of these, the hadrosaurs dominated in terms of sheer number and made up half of all dinosaurs who lived in this region. Vertebrates present in the Horseshoe Canyon Formation at the time of Pachyrhinosaurus included reptiles, and amphibians. Sharks, rays, sturgeons, bowfins, gars and the gar-like Belonostomus made up the fish fauna.
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The formation represents an alluvial to coastal plain setting that was wet, humid, and dominated by large, deep channels with stable banks and perennial wetland swamps, ponds, and lakes. Rivers flowed generally west across the plains and drained into the Western Interior Seaway; the Gulf Coast region of the United States has been proposed as a good modern analogue (such as the current day swamplands of Louisiana). The formation preserves a diverse and abundant range of fossils, including continental and aquatic animals, plants, and palynomorphs (organic microfossils). Three ceratopsids from the Kaiparowits Formation: Utahceratops, Nasutoceratops, and Kosmoceratops (as well as a pachycephalosaur and various paravians) Other ornithischian dinosaurs from the Kaiparowits Formation include ceratopsians such as the chasmosaurine Utahceratops, the centrosaurine Nasutoceratops (and possibly a second yet unnamed centrosaurine), indeterminate pachycephalosaurs, the ankylosaurid Akainacephalus, an indeterminate nodosaurid, the hadrosaurs Gryposaurus and Parasaurolophus, and an indeterminate, basal neornithischian.
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They created their own data matrix and through it found that many groups of ceratopsians could be supported, and that Aquilops was a basal neoceratopsian that could potentially be a protoceratopsid, leptoceratopsid, or ceratopsid, although any one of these groups would have a large ghost lineage with Aquilops. Ajkaceratops was identified as a wildcard taxon that could either place close to Ceratopsoidea or as a very basal neoceratopsian, despite being from the middle Late Cretaceous. All previously published neoceratopsian phylogenetic analyses were incorporated into the analysis of Eric M. Morschhauser and colleagues in 2019, along with all previously published diagnostic species excluding the incomplete juvenile Archaeoceratops yujingziensis and the problematic genera Bainoceratops, Lamaceratops, Platyceratops and Gobiceratops that are very closely related to and potentially synonymous with Bagaceratops. While there were many unresolved areas of the strict consensus, including all of Leptoceratopsidae, a single most parsimonious tree was found that was most consistent with the relative ages of the taxa included, which is shown below.
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Skeletal diagram showing known elements of the holotype specimen (AMNH 6517) The remains of Oviraptor were first discovered by technician George Olsen in a 1923 expedition on the Djadochta Formation led by the North American naturalist Roy Chapman Andrews, and first described by Henry Fairfield Osborn in 1924. Its name is Latin for 'egg taker' or "egg seizer", referring to the fact that the first fossil specimen was discovered atop a pile of what was thought to be Protoceratops eggs, and the specific name philoceratops means "lover of ceratopsians", also given as a result of this find. In his 1924 paper, Osborn explained that the name was given due to the close proximity of the skull of Oviraptor to the nest (it was separated from the eggs by only of sand). However, Osborn also suggested that the name Oviraptor "may entirely mislead us as to its feeding habits and belie its character".
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Holotype skull shown in oblique, top, and right side views Since 2000, the Natural History Museum of Utah (UMNH) and the Bureau of Land Management have been conducting paleontological surveys of the Kaiparowits Formation at the Grand Staircase-Escalante National Monument in southern Utah. This national monument was established in 1996 in part for the preservation and study of its fossils, and the surveys there have yielded a wide array of unique dinosaur fossils. Field crews from other institutions have also participated, and the collaborative effort has been called the Kaiparowits Basin Project. Among the discoveries made were three new ceratopsian (horned dinosaur) taxa, one of which was identified from two localities (UMNH Locality VP 890 and 951) discovered by volunteer field crew member Scott Richardson during the field seasons of 2006 and 2007. It was preliminarily referred to as "Kaiparowits new taxon A" and identified as a chasmosaurine ceratopsid in a 2010 symposium book about ceratopsians.
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The lack of growth lines also means that the individual ages of the Kosmoceratops and Utahceratops specimens cannot be estimated, but Levitt determined that the examined Kosmoceratops specimens were subadult to adult, ruling out Fowler and colleagues' 2011 claim that they represented immature Vagaceratops. She also determined that the largest Kosmoceratops and Utahceratops were adults, and therefore ruled out that one was the juvenile of the other. In a 2017 Master's thesis, paleontologist Nicole Marie Ridgwell described two coprolites (fossilized dung) from the Kaiparowits Formation which, due to their size, may have been produced by a member of one of three herbivorous dinosaur groups known from the formation: ceratopsians (including Kosmoceratops), hadrosaurs, or ankylosaurs (rarest of the three groups). The coprolites contained fragments of angiosperm wood (which indicates a diet of woody browse); though there was previously little evidence of dinosaurs consuming angiosperms, these coprolites showed that dinosaurs adapted to feeding on them (they only became common in the Early Cretaceous, diversifying in the Late Cretaceous).
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Paleomap of North America during the Campanian age; Kosmoceratops lived in southern Laramidia (lower left). Though the area of Laramidia was only 20 percent that of modern North America, it saw a major evolutionary radiation of dinosaurs, including the common hadrosaurs and ceratopsians. It has been postulated that there was a latitudinal array of dinosaur "provinces" or biomes on Laramidia during the Campanian and Maastrichtian ages of the Late Cretaceous, the boundary lying around modern northern Utah and Colorado; the same major clades are known from the north and south but are distinct from each other at the genus and species levels. This hypothesis has been challenged; one argument claims that northern and southern dinosaur assemblages during this time were not coeval but reflect a taxonomic distribution over time, which gives the illusion of geographically isolated provinces, and that the distinct assemblages may be an artifact of sampling bias between geological formations.
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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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A resting Kosmoceratops being disturbed by the troodontid Talos In a 2013 Master's thesis (summarized in a published paper by different authors in 2019), paleontologist Carolyn Gale Levitt histologically studied the long bones of Kosmoceratops (femora of the adult holotype and the assigned subadult or adult UMNH VP 21339) and Utahceratops to examine indicators of growth and maturity in the bone microstructure (until then the only chasmosaurines ever sampled for this). The bone tissue had a high number of osteocytes (bone cells) as well as a dense network of blood vessels, including radially oriented vascular canals (blood canals running towards the bone interior), indicating sustained rapid growth. These features also indicate that ceratopsians had an elevated metabolism and were homeothermic endotherms (or "warm-blooded"), like modern birds and mammals. The Kosmoceratops and Utahceratops bones sampled by Levitt did not show evidence of lines of arrested growth (annual growth lines), and compared with the ceratopsids Pachyrhinosaurus, Centrosaurus, and Einosaurus from further north which did have growth lines, this may indicate that bone growth reacted to climate and that Kosmoceratops and Utahceratops could sustain their growth throughout the year due to their more equitable southern climate.
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