Triceratopsini is a tribe of herbivorous

chasmosaurine 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 ...

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 that lived between the late

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. Campani ...

to the late

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval ...

stages of the

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 ...

period, between 74.73 and 66 million years ago. Fossils of these animals have been found in western North America, in particular West Canada,

Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...

and

Midwestern United States The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...

, which was once part of the ancient 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 ...

. The tribe was named by Nicholas R. Longrich in 2011 for the description of ''

Titanoceratops ''Titanoceratops'' (meaning "titanic horned face") is a controversial genus of herbivorous ceratopsian dinosaur. It was a giant chasmosaurine ceratopsian that lived in the Late Cretaceous period (Campanian stage, about 75 million years agoFowle ...

'', which he defined as "all species closer to '' Triceratops horridus'' than to '' Anchiceratops ornatus'' or '' Arrhinoceratops brachyops''". Triceratopsins were the largest of the chasmosaurines; suggesting that gigantism had evolved in the Ceratopsidae once. In addition there is an evolutionary trend in the solidification of the frills, the most extreme being in ''Triceratops''.

Systematics

The tribe was named by Nicholas R. Longrich in 2011 for the description of ''

'', which he defined as "all species closer to '' Triceratops horridus'' than to '' Anchiceratops ornatus'' or '' Arrhinoceratops brachyops''". Fossils of these animals have been found in western North America, in particular West Canada,

and

, which was once part of the ancient continent of

. The number of species and genera in recent years has been controversial, as some genera such as ''

Torosaurus ''Torosaurus'' ("perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous ceratopsid dinosaur that lived during the late Maastrichtian stage of the Cretaceous period, between 68 and 66 million years ago, th ...

'', ''

Tatankaceratops ''Tatankaceratops'' (meaning "Bison horn face") is a controversial genus of herbivorous ceratopsian dinosaur. It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period (latest Maastrichtian stage) in what is now South ...

'', and ''

Nedoceratops ''Nedoceratops'' (meaning "insufficient horned face") is a controversial genus of ceratopsid dinosaur from the Late Cretaceous period Lance Formation of North America. It is known only from a single skull discovered in Wyoming. Its status is th ...

'' are wrapped up in debate as to whether they are ontogenetic (growth) stages of ''Triceratops'', specimens or species of ''Triceratops'', or unique genera based on

morphometrics Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

. In addition there is a genus, ''

Agathaumas ''Agathaumas'' (; "great wonder") is a dubious genus of a large ceratopsid dinosaur that lived in Wyoming during the Late Cretaceous (late Maastrichtian stage, 66 million years ago). The name comes from grc, αγαν - 'much' and - 'wonder'. It ...

'', which is considered to be a '' nomen dubium'' as it is based on ambiguous fragmentary fossils.Breithaupt, B.H. (1999). "First Discovery of Dinosaurs in the American West." Pp. 59-65 in Gillette, D.D. (ed.), ''Vertebrate Paleontology In Utah''. Utah Geological Survey. , Breithaupt, B.H. (2001). "Passport-In-Time Microvertebrate Fossil Project at the University of Wyoming Geological Museum: Late Cretaceous Paleontological Resources in the Public Eye." Pp. 107-112 in Santucci, V.L., and McClelland, L. (eds.), Proceedings of the 6th Fossil Resources Conference, United States Department of Interior - National Park Services - Geological Resources Division.

Phylogeny

For his phylogenetic analysis of ''Titanoceratops'', Longrich (2011) only recognized three genera, with ''

Eotriceratops ''Eotriceratops'' (meaning "dawn three-horned face") is a genus of herbivorous ceratopsian dinosaurs which lived in the area of North America during the late Cretaceous period. The only named species is ''Eotriceratops xerinsularis''. Discovery ...

'', ''

Ojoceratops ''Ojoceratops'' ( meaning "Ojo Alamo horned face") is a genus of ceratopsian dinosaur which lived in what is now New Mexico, United States. ''Ojoceratops'' fossils have been recovered from strata of the Ojo Alamo Formation (Naashoibito Member), ...

'', and ''

'' resolved as junior synonyms of ''Triceratops'', as well as recognizing ''Torosaurus utahensis'' as a species of ''Triceratops'': In 2015 authors Caleb Brown & Donald Henderson conducted a phylogenetic analysis in the description of '' Regaliceratops'' and found ''Eotriceratops'', ''Ojoceratops'', and ''Nedoceratops'' to be valid genera. There is a polytomy between ''Regaliceratops'', ''Eotriceratops'', ''Ojoceratops'', and a ''Titanoceratops''–''Triceratops'' clade as shown below: Below is the result of a

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

by Jordan Mallon et al. (2016) from their description of '' Spiclypeus shipporum''. ''

'' was removed from the

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 ...

entirely because it was found that it decreases resolution in their analysis because of the authors' new interpretation of epiparietal configurations. '' Regaliceratops'' was not resolved as a member of the Triceratopsini.

References

{{Taxonbar, from=Q11953106 Ceratopsids Chasmosaurines es:Chasmosaurinae

Systematics

Phylogeny

See also

References