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."
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. They may have utilized fermentation to break down plant material with a gut microflora.
Physiology
Ceratopsians probably had the "low mass-specific metabolic rat[e]" typical of large bodied animals. 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.
Paleoecology
thumb|Size comparison of eight ceratopsids|left
The chief predators of ceratopsids were tyrannosaurids.
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. 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.
The Dueling Dinosaurs speciman from the Hell Creek formation shows a Triceratops buried in combat with a Nanotyrannus.
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. In 2004, Peter Dodson defined it to include Triceratops, Centrosaurus, and all descendants of their most recent common ancestor. 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".
See also
- 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.