Centrosaurine
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Centrosaurinae (from the
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
, meaning "pointed lizards") is a subfamily of
ceratopsid 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 ...
, a group of large quadrupedal
ornithischia 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 ...
n
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
. Centrosaurine fossil remains are known primarily from the northern region of
Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Year#SI prefix multipliers, Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island ...
(modern day Alberta, Montana, and Alaska) but isolated taxa have been found in China and Utah as well. Defining features of centrosaurines include a large nasal horn, short supratemporal horns, and an ornamented frill projecting from the back of the skull. With the exception of ''
Centrosaurus apertus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...
'', all adult centrosaurines have spike-like ornaments midway up the skull. Morphometric analysis shows that centrosaurines differ from other ceratopsian groups in skull, snout, and frill shapes. There is evidence to suggest that male centrosaurines had an extended period of adolescence, and sexual
ornamentation An ornament is something used for decoration. Ornament may also refer to: Decoration * Ornament (art), any purely decorative element in architecture and the decorative arts * Ornamental turning * Biological ornament, a characteristic of animals ...
did not appear until adulthood. Centrosaurinae was named by paleontologist
Lawrence Lambe Lawrence Morris Lambe (August 27, 1863 – March 12, 1919) was a Canadian geologist, palaeontologist, and ecologist from the Geological Survey of Canada (GSC). His published work, describing the diverse and plentiful dinosaur discoveries from t ...
in 1915, with ''
Centrosaurus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...
'' as the
type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...
. It is defined in the ''
PhyloCode The ''International Code of Phylogenetic Nomenclature'', known as the ''PhyloCode'' for short, is a formal set of rules governing phylogenetic nomenclature. Its current version is specifically designed to regulate the naming of clades, leaving the ...
'' as "the largest clade containing ''
Centrosaurus apertus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...
'', but not ''
Chasmosaurus belli ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Late Cretaceous Period in North America. Its given name means 'opening lizard', referring to the large openings ( fenestrae) in its frill (Greek ''chasma'', meaning 'opening', 'hollo ...
'' and ''
Triceratops horridus ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...
''. The centrosaurines are further divided into three tribes: the Nasutoceratopsini, the Centrosaurini, and the Pachyrhinosaurini by Ryan ''et al'' (2016). Nasutoceratopsini is defined as "the largest clade containing '' Nasutoceratops titusi'', but not ''
Centrosaurus apertus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...
''. The remaining two tribes belong to the clade Eucentrosaura, defined as "the smallest clade containing ''Centrosaurus apertus'' and ''Pachyrhinosaurus canadensis''". Centrosaurini is defined as "the largest clade containing ''Centrosaurus apertus'', but not ''Pachyrhinosaurus canadensis''" while Pachyrhinosaurini has the opposite definition consisting of "the largest clade containing ''Pachyrhinosaurus canadensis'', but not ''Centrosaurus apertus''". Most recently, Mark Loewen and colleagues in 2024 named the tribe Albertaceratopsini in their description of the new species '' Lokiceratops rangiformis''. It is defined as "all taxa more closely related to '' Albertaceratops nesmoi'' than to ''Centrosaurus apertus''".


Classification

The classification of centrosaurines and the relationships among the various species is complicated by a wide degree of variation between individuals and growth stages. Some features that have traditionally been used to classify these dinosaurs, like the number and arrangement of frill ornaments or spikes, have been discovered to be more variable than previously thought. For example, the
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
presented below follows a 2016 phylogenetic analysis by Chiba ''et al.'' (2017). These authors treated the species ''Rubeosaurus ovatus'' as distinct from ''Styracosaurus albertensis'', and recovered several distinct clades within Centrosaurini, which together formed a sister group to the Pachyrhinosaurini: However, subsequent studies have cast doubt on the usefulness of minor variations in frill spike arrangement for classifying centrosaurines. In particular, large sample sizes of the species ''Centrosaurus apertus'' and ''Styracosaurus albertensis'' have shown a higher than predicted amount of variation. In 2020, Holmes et al. explored what the effect of recognizing such diversity would have on centrosaur classification. They used the same data as Chiba ''et al.s 2017 study, but treated ''Rubeosaurus'' as a synonym of ''Styracosaurus'', dropping it from their taxon list. The resulting cladogram (below) found Centrosaurini as a polytomy, a grouping with no discernable sister group relationships within it. The authors concluded that this meant the variation present within these species made it difficult to find any real resolution among them, and may even provide support for the hypothesis that centrosaurines evolved primarily via
anagenesis Anagenesis is the gradual evolution of a species that continues to exist as an interbreeding population. This contrasts with cladogenesis, which occurs when branching or splitting occurs, leading to two or more lineages and resulting in separate ...
(a single lineage changing through time) rather than cladogenesis (multiple branching lineages with shared common ancestors). Pachyrhinosaurini was defined in 2012 by Fiorillo & Tykoski. It was defined as all centrosaurine ceratopsids more closely related to ''Pachyrhinosaurus canadensis'' than to ''Centrosaurus apertus''. It was defined during the description of ''Pachyrhinosaurus perotorum'', a species from Alaska. The substituent clade Pachyrostra, compromising centrosaurs with bossed instead of horned noses, is defined as "the least inclusive clade including both ''Pachyrhinosaurus canadensis'' and ''Achelousaurus horneri''.


Biogeography

Centrosaurine fossils have mostly been found in Western North America (Alberta, Montana, and Alaska). In the United States, two taxa, '' Diabloceratops and Machairoceratops'', have been found as far south as Utah. ''
Yehuecauhceratops ''Yehuecauhceratops'' (meaning "ancient horned face") is a genus of horned centrosaurinae, centrosaurine ceratopsidae, ceratopsid dinosaur from the Late Cretaceous of Coahuila, Mexico. It contains a single species, ''Y. mudei'', described from t ...
,'' a nasutoceratopsin from
Coahuila Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 31 states of Mexico. The largest city and State Capital is the city of Saltillo; the second largest is Torreón and the thi ...
, Mexico, is the southernmost occurrence of a centrosaurine in North America. No centrosaurine fossils had been uncovered outside Western North America until the 2010 discovery of '' Sinoceratops'' in the
Shandong Province Shandong is a coastal province in East China. Shandong has played a major role in Chinese history since the beginning of Chinese civilization along the lower reaches of the Yellow River. It has served as a pivotal cultural and religious center ...
of
China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. However, some authors question the placement of ''Sinoceratops'' within Centrosaurinae. All other
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
dinosaur groups from North America have also been found in Asia, so the initial absence of Asian centrosaurines had been surprising. The current evidence suggests that Centrosaurinae originated in
Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Year#SI prefix multipliers, Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island ...
90-80 million years ago, with the discovery of the oldest known centrosaurine, ''
Menefeeceratops ''Menefeeceratops'' (meaning "Menefee Formation horned face") is a genus of ceratopsid dinosaur from the Menefee Formation in New Mexico, United States. It is potentially the oldest known member of the ceratopsids, as well as the centrosaurine s ...
'' further proving this. This means ''Sinoceratops'' would have migrated to China from North America. Some hypothesize that centrosaurines originated in southern
Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Year#SI prefix multipliers, Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island ...
and later radiated north.


Body size

Compared to their sister group,
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, durin ...
, centrosaurines are relatively small. The primitive '' Sinoceratops'' is an exception, with an estimated skull length of . By contrast, the skull length of '' Albertoceratops'' was more typical for this group at only . In general, centrosaurines were about the size of a
rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...
with body lengths ranging from .


Reproduction

Possible
neonate In common terminology, a baby is the very young offspring of adult human beings, while infant (from the Latin word ''infans'', meaning 'baby' or 'child') is a formal or specialised synonym. The terms may also be used to refer to Juvenile (orga ...
sized centrosaurine fossils have been documented in the
scientific literature Scientific literature encompasses a vast body of academic papers that spans various disciplines within the natural and social sciences. It primarily consists of academic papers that present original empirical research and theoretical ...
. Research indicates that
centrosaurines Centrosaurinae (from the Greek language, Greek, meaning "pointed lizards") is a subfamily of ceratopsid, a group of large quadrupedal ornithischian dinosaur. Centrosaurine fossil remains are known primarily from the northern region of Laramidia ( ...
did not achieve fully developed mating signals until nearly fully grown. Scott D. Sampson found commonality between the slow growth of mating signals in centrosaurines and the extended
adolescence Adolescence () is a transitional stage of human Developmental biology, physical and psychological Human development (biology), development that generally occurs during the period from puberty to adulthood (typically corresponding to the age o ...
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 an extended adolescence.


See also

*
Timeline of ceratopsian research This timeline of ceratopsian research is a chronological listing of events in the History of paleontology, history of paleontology focused on the ceratopsians, a group of herbivorous marginocephalian dinosaurs that evolved parrot-like beaks, b ...


Footnotes


References

* * Sampson, S. D., 2001, Speculations on the socioecology of Ceratopsid dinosaurs (Orinthischia: Neoceratopsia): In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 263–276. * Tanke, D.H. and Brett-Surman, M.K. 2001. Evidence of Hatchling and Nestling-Size Hadrosaurs (Reptilia:Ornithischia) from Dinosaur Provincial Park (Dinosaur Park Formation: Campanian), Alberta, Canada. pp. 206–218. In: Mesozoic Vertebrate Life—New Research Inspired by the Paleontology of Philip J. Currie. Edited by D.H. Tanke and K. Carpenter. Indiana University Press: Bloomington. xviii + 577 pp. {{Taxonbar, from=Q132304 Dinosaur subfamilies Late Cretaceous dinosaurs