Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, ''Yinlong downsi'', lived between 161.2 and 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.
/ref> The last ceratopsian species, ''Triceratops prorsus'', became extinct during the Cretaceous–Paleogene extinction event, . 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). ''Triceratops'' is by far the best-known ceratopsian to the general public. It is traditional for ceratopsian genus names to end in "''-ceratops''", although this is not always the case. One of the first named genera was ''Ceratops'' itself, which lent its name to the group, although it is considered a ''nomen dubium'' today as its fossil remains have no distinguishing characteristics that are not also found in other ceratopsians.Dodson, P. 1996. ''The Horned Dinosaurs''. Princeton: Princeton University Press. 346pp.


Ceratopsians are easily recognized by features of the skull. On the tip of a ceratopsian upper jaw is the rostral bone, an edentulous (toothless) ossification, unique to ceratopsians. Othniel Charles Marsh recognized and named this bone, which acts as a mirror image of the predentary bone on the lower jaw. This ossification evolved to morphologically aid the mastication of plant matter. 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. Basal Ceratopsia. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). ''The Dinosauria'' (2nd Edition). Berkeley: University of California Press. Pp. 478-493.Dodson, P., Forster, C.A., & Sampson, S.D. 2004. Ceratopsidae. In: Dodson, P., Weishampel, D.B., & Osmolska, H. (Eds.). ''The Dinosauria'' (2nd Edition). 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. Epoccipitals begin as separate bones that fuse during the animal's growth to either the squamosal or parietal bones that make up the base of the frill. These bones were ornamental instead of functional, and may have helped differentiate species. Epoccipitals probably were present in all known ceratopsids with the possible exception of ''Zuniceratops''. They appear to have been broadly different between short-frilled ceratopsids (centrosaurines) and long-frilled ceratopsids (chasmosaurines), being elliptical with constricted bases in the former group, and triangular with wide bases in the latter group. Within these broad definitions, different species would have somewhat different shapes and numbers. In centrosaurines especially, like ''Centrosaurus'', ''Pachyrhinosaurus'', and ''Styracosaurus'', these bones become long and spike- or hook-like. A well-known example is the coarse sawtooth fringe of broad triangular epoccipitals on the frill of ''Triceratops''. When regarding the ossification's morphogenetic traits, it can be described as dermal. The term epoccipital was coined by famous paleontologist Othniel Charles Marsh in 1889.

History of study

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). ''The Ceratopsia''. Government Printing Office, Washington, D.C., 300 pp. During another of Hayden's expeditions in 1872, Fielding Bradford Meek found several giant bones protruding from a hillside in southwestern Wyoming. He alerted paleontologist Edward Drinker Cope, who led a dig to recover the partial skeleton. Cope recognized the remains as a dinosaur, but noted that even though the fossil lacked a skull, it was different from any type of dinosaur then known. He named the new species ''Agathaumas sylvestris'', meaning "marvellous forest-dweller".Gillette, D.D. (1999). ''Vertebrate Paleontology In Utah''. Utah Geological Survey, 554 pp. , Soon after, Cope named two more dinosaurs that would eventually come to be recognized as ceratopsids: ''Polyonax'' and ''Monoclonius''. ''Monoclonius'' was notable for the number of disassociated remains found, including the first evidence of ceratopsid horns and frills. Several ''Monoclonius'' fossils were found by Cope, assisted by Charles Hazelius Sternberg, in summer 1876 near the Judith River in Chouteau County, Montana. 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. This prompted Cope to reexamine his own specimens and to realize that ''Triceratops'', ''Monoclonius'', and ''Agathaumas'' all represented a single group of similar dinosaurs, which he named Agathaumidae in 1891. Cope redescribed ''Monoclonius'' as a horned dinosaur, with a large nasal horn and two smaller horns over the eyes, and a large frill.


Ceratopsia was coined by Othniel Charles Marsh in 1890 to include dinosaurs possessing certain characteristic features, including horns, a rostral bone, teeth with two roots, fused neck vertebrae, and a forward-oriented pubis. Marsh considered the group distinct enough to warrant its own suborder within Ornithischia. The name is derived from the Greek ''κέρας''/''kéras'' meaning 'horn' and ''ὄψῐς''/''ópsis'' meaning 'appearance, view' and by extension 'face'. As early as the 1960s, it was noted that the name ''Ceratopsia'' is actually incorrect linguistically and that it should be ''Ceratopia''.Steel, R. 1969. Ornithischia. In: Kuhn, O. (Ed.). ''Handbuch de Paleoherpetologie'' (Part 15). Stuttgart: Gustav Fischer Verlag. 87pp. However, this spelling, while technically correct, has been used only rarely in the scientific literature, and the vast majority of paleontologists continue to use Ceratopsia. As the ICZN does not govern taxa above the level of superfamily, this is unlikely to change.


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. Most who still employ the use of ranks have retained its traditional ranking of suborder, though some have reduced to the level of infraorder.Benton, M.J. (2004). ''Vertebrate Palaeontology, Third Edition''. Blackwell Publishing, 472 pp. 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.'' No. 113. ''Craspedodon'' from the Late Cretaceous (Santonian) of Belgium may also be a ceratopsian, specifically a neoceratopsian closer to ceratopsoidea than protoceratopsidae. Possible leptoceratopsid remains have also been described from the early Campanian of Sweden.


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. 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. 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. The two presented this analysis again in 2004. In 2005, You and three others, including Dodson, published on ''Auroraceratops'' and inserted this new dinosaur into their phylogeny. In contrast to the previous analysis, You and Dodson find ''Chaoyangsaurus'' to be the most basal neoceratopsian, more derived than ''Psittacosaurus'', while Leptoceratopsidae, not Protoceratopsidae, is recovered as the sister group of Ceratopsidae. This study includes ''Auroraceratops'', but lacks seven taxa found in Xu and Makovicky's work, so it is unclear how comparable the two studies are. ''Asiaceratops'' and ''Turanoceratops'' are each considered ''nomina dubia'' and not included. Xu Xing of the Chinese Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing, along with Peter Makovicky, formerly of the American Museum of Natural History (AMNH) in New York City and others, published a cladistic analysis in the 2002 description of ''Liaoceratops''. This analysis is very similar to one published by Makovicky in 2001.Makovicky, P.J. 2001. A ''Montanoceratops cerorhynchus'' (Dinosauria: Ceratopsia) braincase from the Horseshoe Canyon Formation of Alberta, In: Tanke, D.H. & Carpenter, K. (Eds.). ''Mesozoic Vertebrate Life''. Bloomington: Indiana University Press. Pp. 243-262. Xu and other colleagues added ''Yinlong'' to this analysis in 2006. 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. 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.



Ceratopsia appears to have originated in Asia, as all of the earliest members are found there. Fragmentary remains, including teeth, which appear to be neoceratopsian, are found in North America from the Albian stage (112 to 100 million years ago), indicating that the group had dispersed across what is now the Bering Strait by the middle of the Cretaceous Period. Almost all leptoceratopsids are North American, aside from ''Udanoceratops'', which may represent a separate dispersal event, back into Asia. Ceratopsids and their immediate ancestors, such as ''Zuniceratops'', were unknown outside of western North America, and were presumed endemic to that continent. The traditional view that ceratopsoids originated in North America was called into question by the 2009 discovery of better specimens of the dubious Asian form ''Turanoceratops'', which confirmed it as a ceratopsid. It is unknown whether this indicates ceratopsids actually originated in Asia, or if the ''Turanoceratops'' immigrated from North America.

Individual variation

Unlike almost all other dinosaur groups, skulls are the most commonly preserved elements of ceratopsian skeletons and many species are known only from skulls. There is a great deal of variation between and even within ceratopsian species. Complete growth series from embryo to adult are known for ''Psittacosaurus'' and ''Protoceratops'', allowing the study of ontogenetic variation in these species. Significant sexual dimorphism has been noted in ''Protoceratops'' and several ceratopsids.Lehman, T.M. 1990. The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and systematics. In: Carpenter, K. & Currie, P.J. (Eds.). ''Dinosaur Systematics: Approaches and Perspectives''. Cambridge: Cambridge University Press. Pp. 211-230.

Ecological role

''Psittacosaurus'' and ''Protoceratops'' are the most common dinosaurs in the different Mongolian sediments where they are found. ''Triceratops'' fossils are far and away the most common dinosaur remains found in the latest Cretaceous rocks in the western United States, making up as much as 5/6ths of the large dinosaur fauna in some areas.Bakker, R.T. (1986). ''The Dinosaur Heresies: New Theories Unlocking The Mystery of the Dinosaurs and Their Extinction''. 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. Like modern migratory herds, they would have had a significant effect on their environment, as well as serving as a major food source for predators.

Posture and locomotion

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.

Daily activity patterns

A nocturnal lifestyle has been suggested for the primitive ceratopsian ''Protoceratops''. However, comparisons between the scleral rings of ''Protoceratops'' and ''Psittacosaurus'' and modern birds and reptiles indicate that they may have been cathemeral, active throughout the day at short intervals.


Activity-related bone fractures have been documented in ceratopsians.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336. Periostitis has also been documented in the shoulder blade of a ceratopsian.McWhinney, L., Carpenter, K., and Rothschild, B., 2001, Dinosaurian humeral periostitis: a case of a juxtacortical lesion in the fossil record: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 364-377.

Timeline of genera

ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-201.3 till:-45 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:10 start:-200 ScaleMinor = unit:year increment:1 start:-201 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:jurassic value:rgb(0.2,0.7,0.79) id:earlyjurassic value:rgb(0,0.69,0.89) id:middlejurassic value:rgb(0.52,0.81,0.91) id:latejurassic value:rgb(0.74,0.89,0.97) id:cretaceous value:rgb(0.5,0.78,0.31) id:earlycretaceous value:rgb(0.63,0.78,0.65) id:latecretaceous value:rgb(0.74,0.82,0.37) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2 bar:NAM3 bar:NAM4 bar:NAM5 bar:NAM23 bar:NAM6 bar:NAM7 bar:NAM8 bar:NAM9 bar:NAM10 bar:NAM11 bar:NAM12 bar:NAM25 bar:NAM13 bar:NAM14 bar:NAM15 bar:NAM16 bar:NAM17 bar:NAM26 bar:NAM18 bar:NAM19 bar:NAM20 bar:NAM21 bar:NAM22 bar:NAM24 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -201.3 till: -174.1 color:earlyjurassic text:Early from: -174.1 till: -163.5 color:middlejurassic text:Middle from: -163.5 till: -145 color:latejurassic text:Late from: -145 till: -100.5 color:earlycretaceous text:Early from: -100.5 till: -66 color:latecretaceous text:Late bar:eratop from: -201.3 till: -145 color:jurassic text:Jurassic from: -145 till: -66 color:cretaceous text:Cretaceous PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:latejurassic bar:NAM1 from:-168.3 till:-166.1 text:Chaoyangsaurus color:latejurassic bar:NAM2 from:-162 till:-160 text:Yinlong color:latejurassic bar:NAM3 from:-162 till:-160 text:Hualianceratops color:latejurassic bar:NAM4 from:-152 till:-145 text:Xuanhuaceratops color:earlycretaceous bar:NAM5 from:-145 till:-140 text:Stenopelix color:earlycretaceous bar:NAM23 from:-139.8 till:-129.4 text:Albalophosaurus color:earlycretaceous bar:NAM6 from:-129.4 till:-100.5 text:Psittacosaurus color:earlycretaceous bar:NAM7 from:-126 till:-119 text:Liaoceratops color:earlycretaceous bar:NAM8 from:-113 till:-103 text:Koreaceratops color:earlycretaceous bar:NAM9 from:-113 till:-100.5 text:Archaeoceratops color:earlycretaceous bar:NAM10 from:-113 till:-88 text:Helioceratops color:earlycretaceous bar:NAM11 from:-108 till:-104 text:Aquilops color:earlycretaceous bar:NAM12 from:-107 till:-100.5 text:Auroraceratops color:earlycretaceous bar:NAM25 from:-105 till:-100.5 text:Kulceratops color:latecretaceous bar:NAM13 from:-100.5 till:-96 text:Asiaceratops color:latecretaceous bar:NAM14 from:-100.5 till:-83.6 text:Graciliceratops color:latecretaceous bar:NAM15 from:-93 till:-89.8 text:Turanoceratops color:latecretaceous bar:NAM16 from:-93 till:-89.8 text:Zuniceratops color:latecretaceous bar:NAM17 from:-93 till:-78 text:Mosaiceratops color:latecretaceous bar:NAM26 from:-86.3 till:-83.6 text:Craspedodon color:latecretaceous bar:NAM18 from:-86.3 till:-83.6 text:Ajkaceratops color:latecretaceous bar:NAM19 from:-86.3 till:-72.1 text:Yamaceratops color:latecretaceous bar:NAM20 from:-85 till:-66 text:Leptoceratopsidae color:latecretaceous bar:NAM21 from:-83.6 till:-72.1 text:Protoceratopsidae color:latecretaceous bar:NAM22 from:-81 till:-66 text:Ceratopsidae color:latecretaceous bar:NAM24 from:-70 till:-69 text:Micropachycephalosaurus PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -201.3 till: -174.1 color:earlyjurassic text:Early from: -174.1 till: -163.5 color:middlejurassic text:Middle from: -163.5 till: -145 color:latejurassic text:Late from: -145 till: -100.5 color:earlycretaceous text:Early from: -100.5 till: -66 color:latecretaceous text:Late bar:era from: -201.3 till: -145 color:jurassic text:Jurassic from: -145 till: -66 color:cretaceous text:Cretaceous


External links

Introduction to the Ceratopsians
University of California Museum of Paleontology

at Palaeos.com (technical) {{Taxonbar|from=Q131381 Category:Marginocephalians Category:Late Jurassic first appearances Category:Maastrichtian extinctions Category:Taxa named by Othniel Charles Marsh