Ceratopsidae (sometimes spelled Ceratopidae) is a family of
ceratopsian
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. ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s including ''
Triceratops
''Triceratops'' ( ; ) is a genus of herbivore, herbivorous Chasmosaurinae, chasmosaurine Ceratopsidae, ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous Period (geology), period, about 68 m ...
'', ''
Centrosaurus
''Centrosaurus'' ( ; ) is a genus of herbivorous ceratopsian dinosaur from the Late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago.
Discovery and naming
The firs ...
'', and ''
Styracosaurus
''Styracosaurus'' ( ; meaning "spiked lizard" from the Ancient Greek / "spike at the butt-end of a spear-shaft" and / "lizard") is a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 75.5 to 74.5&nbs ...
''. All known
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
were quadrupedal
herbivores
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
from the Upper
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
. All but one species are known from western
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, which formed the island continent of
Laramidia
Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from A ...
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
Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-avian dinosaurs, during ...
and
Centrosaurinae
Centrosaurinae (from the Greek, meaning "pointed lizards") is a subfamily of ceratopsid dinosaurs, a group of large quadrupedal ornithischians. Centrosaurine fossil remains are known primarily from the northern region of Laramidia (modern day Al ...
. 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.
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
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
s is one possible purpose – although the frills are comparatively fragile in many species – but it is more likely that, as in modern
ungulates
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...
, they were
secondary sexual characteristics
Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a sp ...
used in displays or for
intraspecific combat. The massive bosses on the skulls of ''
Pachyrhinosaurus
''Pachyrhinosaurus'' (meaning in Greek "thick-nosed lizard", from ' (), thick; ' (), nose; and (), lizard) is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discove ...
'' and ''
Achelousaurus
''Achelousaurus'' () is a genus of centrosaurine ceratopsid dinosaur that lived during the Late Cretaceous Period of what is now North America, about 74.2 million years ago. The first fossils of ''Achelousaurus'' were collected in Mont ...
'' resemble those formed by the base of the horns in modern
musk oxen
Musk ( Persian: مشک, ''Mushk'') is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial sub ...
, 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
A herd is a social group of certain animals of the same species, either wildness, wild or Domestication, domestic. The form of collective animal behavior associated with this is called ''herding''. These animals are known as gregarious animal ...
.
Paleobiology
Behavior
Fossil deposits dominated by large numbers of ceratopsids from individual species suggest that these animals were at least somewhat social.
However, the exact nature of ceratopsid social behavior has historically been controversial.
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.
Other authors, such as Scott D. Sampson, interpret these deposits as the remains of large "socially complex" herds.
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
Centrosaurinae (from the Greek, meaning "pointed lizards") is a subfamily of ceratopsid dinosaurs, a group of large quadrupedal ornithischians. Centrosaurine fossil remains are known primarily from the northern region of Laramidia (modern day Al ...
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
Adolescence () is a transitional stage of physical and psychological development that generally occurs during the period from puberty to adulthood (typically corresponding to the age of majority). Adolescence is usually associated with the t ...
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.
Females, by contrast do not have such extended adolescence.
Other researchers who support the idea of ceratopsid herding have speculated that these associations were seasonal.
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.
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.
Many African herding animals engage in this kind of seasonal herding today.
Herds would also have afforded some level of protection from the chief predators of ceratopsids,
tyrannosaurids
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family (biology), family of coelurosaurian Theropoda, theropod dinosaurs that comprises two subfamilies containing up to thirteen genus, genera, including the eponymous ''Tyrannos ...
.
Diet
![Ceratopsidae Tooth](https://upload.wikimedia.org/wikipedia/commons/3/38/Ceratopsidae_Tooth.jpg)
Ceratopsids were adapted to processing high-
fiber
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...
plant material with their highly derived
dental batteries
Dinosaur teeth have been studied since 1822 when Mary Ann Mantell (1795-1869) and her husband Dr Gideon Algernon Mantell (1790-1852) discovered an ''Iguanodon'' tooth in Sussex in England. Unlike mammal teeth, individual dinosaur teeth are gener ...
and advanced dentition.
They may have utilized
fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
to break down plant material with a gut
microflora
Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found to ...
.
Mallon et al. (2013) examined herbivore coexistence on the island continent of
Laramidia
Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from A ...
, during the Late Cretaceous. It was concluded that ceratopsids were generally restricted to feeding on vegetation at, or below, the height of 1 meter.
Physiology
Ceratopsians probably had the "low mass-specific metabolic rat
typical of large bodied animals.
Sexual dimorphism
![Ceratopsian skulls](https://upload.wikimedia.org/wikipedia/commons/3/30/Ceratopsian_skulls.jpg)
According to Scott D. Sampson, if ceratopsids were to have
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
modern ecological analogues suggest it would be in their mating signals like horns and frills.
No convincing evidence for sexual dimorphism in body size or mating signals is known in ceratopsids, although was present in the more primitive ceratopsian ''
Protoceratops andrewsi
''Protoceratops'' (; ) is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus ''Protoceratops'' includes two species: ''P. andrewsi'' and the larger ''P. hellenik ...
'' whose sexes were distinguishable based on frill and nasal prominence size.
This is consistent with other known
tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...
groups where midsized animals tended to exhibit markedly more sexual dimorphism than larger ones.
However, if there were sexually dimorphic traits, they may have been soft tissue variations like colorations or
dewlap
A dewlap is a longitudinal flap of skin or similar flesh that hangs beneath the lower jaw or neck of many vertebrates. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibula ...
s that would not have been preserved as fossils.
Evolution
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."
The earliest ceratopsids, including members of both Centrosaurinae and Chasmosaurinae are known from the early
Campanian
The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...
stage, though the fossil record for early ceratopsids is poor. All but one of the named species of ceratopsid is known from Western North America, which formed the island continent of
Laramidia
Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from A ...
during the Late Cretaceous, separated from the island continent of
Appalachia
Appalachia () is a cultural region in the Eastern United States that stretches from the Southern Tier of New York State to northern Alabama and Georgia. While the Appalachian Mountains stretch from Belle Isle in Newfoundland and Labrador, Ca ...
to the east by the
Western Interior Seaway
The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient sea, ...
. The latitudinal range of ceratopsians across Laramidia extends from Alaska to Mexico. The named ceratopsid outside of Laramidia is ''
Sinoceratops
''Sinoceratops'' is an extinct genus of ceratopsian dinosaur that lived approximately 73 million years ago during the latter part of the Cretaceous Period in what is now Shandong province in China. It was named in 2010 by Xu Xing ''et al.'' f ...
'', a centrosaurine from the late Campanian of China. 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.
Paleoecology
![Ceratopsidae Scale](https://upload.wikimedia.org/wikipedia/commons/7/72/Ceratopsidae_Scale.svg)
The chief predators of ceratopsids were
tyrannosaurids
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family (biology), family of coelurosaurian Theropoda, theropod dinosaurs that comprises two subfamilies containing up to thirteen genus, genera, including the eponymous ''Tyrannos ...
.
There is evidence for an aggressive interaction between a ''
Triceratops
''Triceratops'' ( ; ) is a genus of herbivore, herbivorous Chasmosaurinae, chasmosaurine Ceratopsidae, ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous Period (geology), period, about 68 m ...
'' and a ''Tyrannosaurus'' in the form of partially healed tyrannosaur tooth marks on a ''Triceratops'' brow horn and
squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone.
In most tetrapods, the squamosal and quadratojugal The quadratojugal is a skull bone present in many vertebrates, including ...
(a bone of the
neck frill
A neck frill is the relatively extensive margin seen on the back of the heads of reptiles with either a bony support such as those present on the skulls of dinosaurs of the suborder Marginocephalia or a cartilaginous one as in the frill-necked ...
); 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
Peter Dodson (born August 20, 1946) is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs a ...
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.
Classification
The
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
Ceratopsidae was in 1998 defined by
Paul Sereno
Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago and a National Geographic "explorer-in-residence" who has discovered several new dinosaur species on several continents, including at sites ...
as the group including the
last common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
of ''
Pachyrhinosaurus
''Pachyrhinosaurus'' (meaning in Greek "thick-nosed lizard", from ' (), thick; ' (), nose; and (), lizard) is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discove ...
'' and ''Triceratops''; and all its descendants.
In 2004, it was by
Peter Dodson
Peter Dodson (born August 20, 1946) is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs a ...
defined to include ''
Triceratops
''Triceratops'' ( ; ) is a genus of herbivore, herbivorous Chasmosaurinae, chasmosaurine Ceratopsidae, ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous Period (geology), period, about 68 m ...
'', ''
Centrosaurus
''Centrosaurus'' ( ; ) is a genus of herbivorous ceratopsian dinosaur from the Late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago.
Discovery and naming
The firs ...
'', and all descendants of their most recent common ancestor.
See also
*
Timeline of ceratopsian research
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, spe ...
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.
Footnotes
External links
*
*
{{Portal bar, Dinosaurs, Cretaceous, United States, Asia, Biology
Campanian first appearances
Maastrichtian extinctions
Taxa named by Othniel Charles Marsh
Prehistoric dinosaur families