{{short description|Family of dinosaurs including Triceratops and relatives}} {{Automatic taxobox | name = Ceratopsids | fossil_range = Late Cretaceous,<br />~{{Fossil range|82|66|ref=<ref name="dalman2021">{{cite journal | last1=Dalman | first1=Sebastian G. | last2=Lucas | first2=Spencer G. | last3=Jasinki | first3=Steven G. | last4=Lichtig | first4=Asher J. | last5=Dodson | first5=Peter | url=https://www.researchgate.net/publication/351466021 | title=The oldest centrosaurine: a new ceratopsid dinosaur (Dinosauria: Ceratopsidae) from the Allison Member of the Menefee Formation (Upper Cretaceous, early Campanian), northwestern New Mexico, USA | journal=PalZ | year=2021 | volume=95 | issue=2 | pages=291–335 | doi=10.1007/s12542-021-00555-w | bibcode=2021PalZ...95..291D |issn=0031-0220| s2cid=234351502 }}</ref>}} | image = Ceratopsidae Diversity.jpg | image_caption = Montage of four ceratopsids. Clockwise from top left: ''Titanoceratops'', ''Styracosaurus'', ''Utahceratops'' and ''Triceratops'' | display_parents = 2 | type_species_authority = Marsh, 1888 | taxon = Ceratopsidae | authority = Marsh, 1888 | subdivision_ranks = Subgroups | subdivision = *{{extinct}}''Ceratops'' *{{extinct}}''Dysganus'' *{{extinct}}''Polyonax'' *{{extinct}}Centrosaurinae *{{extinct}}Chasmosaurinae | synonyms = *'''Agathaumidae''' <small>Cope, 1891</small> *'''Torosauridae''' <small>Nopcsa, 1915</small> }}'''Ceratopsidae''' (sometimes spelled '''Ceratopidae''') is a family of ceratopsian dinosaurs including ''Triceratops'', ''Centrosaurus'', and ''Styracosaurus''. All known species were quadrupedal herbivores from the Upper Cretaceous. All but one species are known from western North America, which formed the island continent of Laramidia during most of the Late Cretaceous. Ceratopsids are characterized by beaks, rows of shearing teeth in the back of the jaw, elaborate nasal horns, and a thin parietal-squamosal shelf that extends back and up into a frill. The group is divided into two subfamilies—Chasmosaurinae and Centrosaurinae. The chasmosaurines are generally characterized by long, triangular frills and well-developed brow horns. The centrosaurines had well-developed nasal horns or nasal bosses, shorter and more rectangular frills, and elaborate spines on the back of the frill. The name ''ceratops'' is derived from Ancient Greek, meaning "horned face."<ref name="princetonencyc">{{cite book |last1=Jones |first1=Bryce |title=The Princeton Encyclopedia of Dinosaurs: Ornithischians |date=2026 |publisher=Princeton University Press |url=https://www.google.com/books/edition/The_Princeton_Encyclopedia_of_Dinosaurs/jHlyEQAAQBAJ?hl=en&gbpv=0 |access-date=15 March 2026}}</ref>
These horns and frills show remarkable variation and are the principal means by which the various species have been recognized. Their purpose is not entirely clear. Defense against predators is one possible purpose – although the frills are comparatively fragile in many species – but it is more likely that, as in modern ungulates, they were secondary sexual characteristics used in displays or for intraspecific combat. The massive bosses on the skulls of ''Pachyrhinosaurus'' and ''Achelousaurus'' resemble those formed by the base of the horns in modern musk oxen, suggesting that they butted heads. Centrosaurines have frequently been found in massive bone beds with few other species present, suggesting that the animals lived in large herds.
==Paleobiology==
===Behavior=== Fossil deposits dominated by large numbers of ceratopsids from individual species suggest that these animals were at least somewhat social.<ref name="socioecology-abs-263" /> However, the exact nature of ceratopsid social behavior has historically been controversial.<ref name="socioecology-intro-264" /> In 1997, Lehman argued that the aggregations of many individuals preserved in bonebeds originated as local "infestations" and compared them to similar modern occurrences in crocodiles and tortoises.<ref name="socioecology-intro-264" /> Other authors, such as Scott D. Sampson, interpret these deposits as the remains of large "socially complex" herds.<ref name="socioecology-intro-264" />
Modern animals with mating signals as prominent as the horns and frills of ceratopsians tend to form these kinds of large, intricate associations.<ref name="socioecology-socioecology-267-268" /> Sampson found in previous work that the centrosaurine ceratopsids did not achieve fully developed mating signals until nearly fully grown.<ref name="socioecology-retarded-270" /> 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.<ref name="socioecology-retarded-270" /> 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.<ref name="socioecology-correlates-265" /> Females, by contrast do not have such extended adolescence.<ref name="socioecology-correlates-265" />
Other researchers who support the idea of ceratopsid herding have speculated that these associations were seasonal.<ref name="socioecology-resource-269" /> This hypothesis portrays ceratopsids as living in small groups near the coasts during the rainy season and inland with the onset of the dry season.<ref name="socioecology-resource-269" /> Support for the idea that ceratopsids formed herds inland comes from the greater abundance of bonebeds in inland deposits than coastal ones. The migration of ceratopsids away from the coasts may have represented a move to their nesting grounds.<ref name="socioecology-resource-269" /> Many African herding animals engage in this kind of seasonal herding today.<ref name="socioecology-resource-269" /> Herds would also have afforded some level of protection from the chief predators of ceratopsids, tyrannosaurids.<ref name="socioecology-pred-272" />
===Diet=== thumb|Ceratopsid teeth have a distinctive leaf shape with a primary ridge running down the middle.|left Ceratopsids were adapted to processing high-fiber plant material with their highly derived dental batteries and advanced dentition;<ref name="socioecology-resource-268" /> their skull morphology is consistent with specialisation for feeding on mechanically challenging, low-growing plants.<ref>{{Cite journal |last1=Mallon |first1=Jordan C. |last2=Anderson |first2=Jason S. |date=10 July 2013 |editor-last=Butler |editor-first=Richard J. |title=Skull Ecomorphology of Megaherbivorous Dinosaurs from the Dinosaur Park Formation (Upper Campanian) of Alberta, Canada |url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067182 |journal=PLoS ONE |language=en |volume=8 |issue=7 |article-number=e67182 |doi=10.1371/journal.pone.0067182 |doi-access=free|issn=1932-6203 |pmc=3707905 |pmid=23874409 |access-date=8 February 2026 |via=PLOS ONE}}</ref> They may have utilized fermentation to break down plant material with a gut microflora.<ref name="socioecology-resource-268" /> Mallon et al. (2013) examined herbivore coexistence on the island continent of Laramidia, during the Late Cretaceous. It was concluded that ceratopsids were generally restricted to feeding on vegetation at, or below, the height of 1 meter.<ref>{{cite journal|last1=Mallon|first1=Jordan C|author2=David C Evans|author3=Michael J Ryan|author4=Jason S Anderson|title=Feeding height stratification among the herbivorous dinosaurs from the Dinosaur Park Formation (upper Campanian) of Alberta, Canada|journal=BMC Ecology|year=2013|volume=13|issue=1 |doi=10.1186/1472-6785-13-14|page=14|pmid=23557203|pmc=3637170 |doi-access=free |bibcode=2013BMCE...13...14M }}</ref>
===Physiology=== {{Main|Dinosaur physiology}} Ceratopsians probably had the "low mass-specific metabolic rat[e]" typical of large bodied animals.<ref name="socioecology-resource-268" />
===Sexual dimorphism=== [[File:Ceratopsian skulls.jpg|thumb|Ceratopsid skulls at the Natural History Museum of Utah|left]] According to Scott D. Sampson, if ceratopsids were to have sexual dimorphism modern ecological analogues suggest it would be in their mating signals like horns and frills.<ref name="socioecology-dimorphism-269" /> No convincing evidence for sexual dimorphism in body size or mating signals is known in ceratopsids, although it was present in the more primitive ceratopsian ''Protoceratops andrewsi'', whose sexes were distinguishable based on frill and nasal prominence size.<ref name="socioecology-dimorphism-269" /> This is consistent with other known tetrapod groups where midsized animals tended to exhibit markedly more sexual dimorphism than larger ones.<ref name="socioecology-dimorphism-270" /> However, if there were sexually dimorphic traits, they may have been soft tissue variations like colorations or dewlaps that would not have been preserved as fossils.<ref name="socioecology-dimorphism-270" />
==Evolution== left|thumb|Map of North America during the Late Cretaceous Scott D. Sampson has compared the evolution of ceratopsids to that of some mammal groups: both were rapid from a geological perspective and precipitated the simultaneous evolution of large body size, derived feeding structures, and "varied hornlike organs."<ref name="socioecology-intro-264" /> The earliest ceratopsids, including members of both Centrosaurinae and Chasmosaurinae are known from the early Campanian stage, though the fossil record for early ceratopsids is poor.<ref>{{Cite journal|last=Brown|first=Caleb M.|date=2018-01-16|title=Long-horned Ceratopsidae from the Foremost Formation (Campanian) of southern Alberta|journal=PeerJ|language=en|volume=6|article-number=e4265|pmid=29362697|doi=10.7717/peerj.4265|issn=2167-8359|pmc=5774296 |doi-access=free }}</ref> All but one of the named species of ceratopsid is known from Western North America, which formed the island continent of Laramidia during the Late Cretaceous, separated from the island continent of Appalachia to the east by the Western Interior Seaway. The latitudinal range of ceratopsians across Laramidia extends from Alaska to Mexico. The only named ceratopsid outside of Laramidia is ''Sinoceratops'', a centrosaurine from the late Campanian of China.<ref name="dalman2021"/> An indeterminate tooth of a ceratopsid is known from Mississippi dating to the late Maastrichtian, a few million years prior to the close of the Cretaceous, indicating that ceratopsids dispersed into eastern North America corresponding to the closure of the Western Interior Seaway at the end of the Cretaceous.<ref>{{Cite journal|last1=Farke|first1=Andrew A.|last2=Phillips|first2=George E.|date=23 May 2017|title=The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)|journal=PeerJ|language=en|volume=5|article-number=e3342| pmid=28560100 | doi=10.7717/peerj.3342|issn=2167-8359|pmc=5444368 |doi-access=free }}</ref>
==Paleoecology== thumb|Size comparison of eight ceratopsids|left The chief predators of ceratopsids were tyrannosaurids.<ref name="socioecology-pred-272" /> ''δ''<sup>44/42</sup>Ca ratios in tyrannosaurids indicate that ceratopsids were among their most preferred prey.<ref>{{Cite journal |last1=Michailow |first1=Mateusz M. |last2=Lugli |first2=Federico |last3=Cipriani |first3=Anna |last4=Della Giustina |first4=Francesco |last5=Ferretti |first5=Annalisa |last6=Malferrari |first6=Daniele |last7=Fowler |first7=Denver |last8=Fowler |first8=Elizabeth Freedman |last9=Weber |first9=Michael |last10=Tütken |first10=Thomas |date=1 July 2025 |title=Combined Ca, Sr isotope and trace element analyses of Late Cretaceous dinosaur teeth: assessing diet versus diagenesis |url=https://www.sciencedirect.com/science/article/pii/S001670372500239X |journal=Geochimica et Cosmochimica Acta |language=en |volume=400 |pages=172–189 |doi=10.1016/j.gca.2025.05.006 |access-date=3 October 2025 |via=Elsevier Science Direct|hdl=11380/1380510 |hdl-access=free }}</ref>
There is evidence for an aggressive interaction between a ''Triceratops'' and a ''Tyrannosaurus'' in the form of partially healed tyrannosaur tooth marks on a ''Triceratops'' brow horn and squamosal (a bone of the neck frill); the bitten horn is also broken, with new bone growth after the break. It is not known what the exact nature of the interaction was, though: either animal could have been the aggressor.<ref name=JH08>{{Cite book|last=Happ |first=John |author2=Carpenter, Kenneth |chapter=An analysis of predator–prey behavior in a head-to-head encounter between ''Tyrannosaurus rex'' and ''Triceratops'' |editor=Carpenter, Kenneth |editor2=Larson, Peter E. |title=Tyrannosaurus rex, the Tyrant King (Life of the Past) |publisher=Indiana University Press |location=Bloomington |year=2008 |pages=355–368 |isbn=978-0-253-35087-9}}</ref> Since the ''Triceratops'' wounds healed, it is most likely that the ''Triceratops'' survived the encounter and managed to overcome the ''Tyrannosaurus''. Paleontologist Peter Dodson estimates that in a battle against a bull ''Tyrannosaurus'', the ''Triceratops'' had the upper hand and would successfully defend itself by inflicting fatal wounds to the ''Tyrannosaurus'' using its sharp horns.<ref>Dodson, Peter, ''The Horned Dinosaurs'', Princeton Press. p.19</ref>
The Dueling Dinosaurs speciman from the Hell Creek formation shows a ''Triceratops'' buried in combat with a ''Nanotyrannus''.<ref>{{Cite web |title=The Peculiar Case of the Dueling Dinosaurs |url=https://missouririvermt.com/blog/the-peculiar-case-of-the-dueling-dinosaurs |access-date=April 20, 2026 |website=missouririvermt.com}}</ref><ref>{{Cite web |title=''Nanotyrannus'' Confirmed |url=https://duelingdinosaurs.org/ |access-date=April 20, 2026 |website=duelingdinosaurs.org}}</ref>
==Classification== The clade Ceratopsidae was in 1998 defined by Paul Sereno as the group including the last common ancestor of ''Pachyrhinosaurus'' and ''Triceratops''; and all its descendants.<ref>{{cite journal | last1 = Sereno | first1 = P. C. | year = 1998 | title = A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria | journal = Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen | volume = 210 | pages = 41–83 | doi = 10.1127/njgpa/210/1998/41 }}</ref> In 2004, Peter Dodson defined it to include ''Triceratops'', ''Centrosaurus'', and all descendants of their most recent common ancestor.<ref name=FS04>{{cite book |editor1=Weishampel, David B. |editor2=Dodson, Peter |editor3=Osmólska, Halszka |title=The Dinosauria |edition=2nd |year=2004|publisher=University of California Press |place=Berkeley |isbn=0-520-24209-2}}</ref> Ceratopsidae was given an official definition in the ''PhyloCode'' by Daniel Madzia and colleagues in 2021 as "the smallest clade containing ''Centrosaurus apertus'', ''Ceratops montanus'', ''Chasmosaurus belli'', and ''Triceratops horridus''".<ref name="madziaea21"/> This definition ensures that the type species of Ceratopsidae, ''Ceratops montanus'', is included in the clade's definition.<ref name="madziaea21">{{cite journal |last1=Madzia |first1=D. |last2=Arbour |first2=V.M. |last3=Boyd |first3=C.A. |last4=Farke |first4=A.A. |last5=Cruzado-Caballero |first5=P. |last6=Evans |first6=D.C. |title=The phylogenetic nomenclature of ornithischian dinosaurs |journal=PeerJ |date=2021 |volume=9 |article-number=e12362 |doi=10.7717/peerj.12362|doi-access=free |pmid=34966571 |pmc=8667728 }}</ref>
==See also== {{Portal|Dinosaurs}} * Timeline of ceratopsian research
==References== * Dodson, P. (1996). ''The Horned Dinosaurs''. Princeton University Press, Princeton, New Jersey, pp. xiv-346 * Dodson, P., & Currie, P. J. (1990). "Neoceratopsia." 593–618 ''in'' Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.), 1990: ''The Dinosauria''. University of California Press, Berkeley, Los Angeles, Oxford, 1990 xvi-733. * Sampson, S. D., 2001, Speculations on the socioecology of Ceratopsid dinosaurs (Ornithischia: Neoceratopsia): In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 263–276.
==References== {{Reflist|3|refs= <ref name="socioecology-abs-263">"Abstract", Sampson (2001); page 263.</ref> <ref name="socioecology-intro-264">"Introduction", Sampson (2001); page 264.</ref> <ref name="socioecology-socioecology-267-268">"Ceratopsid Socioecology", Sampson (2001); pages 267–268.</ref> <ref name="socioecology-resource-268">"Resource Exploitation and Habitat", Sampson (2001); page 268.</ref> <ref name="socioecology-resource-269">"Resource Exploitation and Habitat", Sampson (2001); page 269.</ref> <ref name="socioecology-dimorphism-269">"Sexual Dimorphism", Sampson (2001); page 269.</ref> <ref name="socioecology-dimorphism-270">"Sexual Dimorphism", Sampson (2001); page 270.</ref> <ref name="socioecology-retarded-270">"Retarded Growth of Mating Signals", Sampson (2001); page 270.</ref> <ref name="socioecology-correlates-265">"Sociological Correlates in Extant Vertebrates", Sampson (2001); page 265.</ref> <ref name="socioecology-pred-272">"Predation Pressure", Sampson (2001); page 272.</ref> }}
==External links== *{{Commons category-inline}} *{{Wikispecies-inline}}
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Category:Ceratopsidae Category:Dinosaur families Category:Late Cretaceous dinosaurs