Protoceratopsid

Protoceratopsids Temporal range: Late Cretaceous, 85–71 Ma PreЄ Є O S D C P T J K Pg N
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Protoceratops andrewsi skeleton, Carnegie Museum of Natural History
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	†Ornithischia
Parvorder:	†Coronosauria
Family:	†Protoceratopsidae Granger & Gregory, 1923
Type species
†Protoceratops andrewsi Granger & Gregory, 1923
Subgroups
†Protoceratops †Bagaceratopidae †Ajkaceratops †Bagaceratops †Breviceratops †Gobiceratops †Lamaceratops †Magnirostris †Platyceratops

A protoceratopsid is a dinosaur of the family Protoceratopsidae. The name 'protoceratopsid' is derived from Greek for 'first horned face'. They resembled and were closely related to, ceratopsids but were generally smaller and more primitive. Protoceratopsids have so far been found exclusively in the Late Cretaceous of Asia (Nemegt Basin), dating to between about 99.6 and 70.6 million years ago. A typical protoceratopsid is Protoceratops andrewsi.

The taxon Protoceratopsidae was introduced by Walter W. Granger and William King Gregory in May 1923 as a monotypic family for Protoceratops andrewsi. Granger and Gregory recognized Protoceratops' close relationship to other Ceratopsia, but considered it primitive enough to warrant its own family, and perhaps suborder. Protoceratopsidae was later expanded to include all ceratopsians that were too advanced to be psittacosaurids, but too primitive to be ceratopsids. In 1998, Paul Sereno defined Protoceratopsidae as the stem-based clade including "all coronosaurs closer to Protoceratops than to Triceratops." Sereno's definition ensures that Protoceratopsidae is monophyletic, but probably excludes some dinosaurs that have been traditionally thought of as protoceratopsids (for example, Leptoceratops and Montanoceratops). The latter genera are now often classified in a mostly North American family Leptoceratopsidae.

Sereno (2000) included three genera in Protoceratopsidae: Protoceratops, Bagaceratops, and Graciliceratops. Derived characters shared by these dinosaurs include a narrow strap-shaped paroccipital process, a very small occipital condyle, and an upturned dorsal margin of the predentary. In Protoceratops and Bagaceratops (and also in the non-protoceratopsid Leptoceratops), there is a blade-shaped parietal sagittal crest (Sereno 2000: 505). Several other more recently recognized genera may also be protoceratopsids. In 2003, Vladimir Alifanov named, but did not define, a new ceratopsian family Bagaceratopidae to include Bagaceratops, Platyceratops, Lamaceratops and Breviceratops. However, applying Sereno's phylogenetic definition, Alifanov's Bagaceratopidae appears to be a subclade of Protoceratopsidae.

See also

• Timeline of ceratopsian research

References

• Alifanov, V.R., 2003. Two new dinosaurs of the Infraorder Neoceratopsia (Ornithischia) from the Upper Cretaceous of the Nemegt Depression, Mongolian People's Republic. Paleontological Journal 37 (5): 524-535.
• Granger, W. & W.K. Gregory, 1923. Protoceratops andrewsi, a pre-ceratopsian dinosaur from Mongolia. American Museum Novitates 72: 1-9.
• Sereno, P.C., 1998. A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. N. Jb. Geol. Palaont. Abh. 210 (1): 41-83.
• Sereno, P.C., 2000. The fossil record, systematics and evolution of pachycephalosaurs and ceratopsians from Asia. 480-516 in Benton, M.J., M.A. Shishkin, D.M. Unwin & E.N. Kurochkin (eds.), The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge.