Protoceratopsid

Taxobox
name = Protoceratopsids
fossil_range = Late Cretaceous

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image_width = 250px
image_caption = Mounted "Protoceratops" skeleton, Experimentarium, Copenhagen.
regnum = Animalia
phylum = Chordata
infraclassis = Sauropsida
superordo = Dinosauria
ordo = Ornithischia
subordo = Cerapoda
infraordo = Ceratopsia
familia = Protoceratopsidae
familia_authority = Granger & Gregory, 1923
subdivision_ranks = Genera
subdivision = ? "Bagaceratops"
? "Breviceratops"
"Graciliceratops"
? "Lamaceratops"
"Magnirostris"
? "Platyceratops"
"Protoceratops" (type)
"Serendipaceratops"

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). A typical protoceratopsid is "Protoceratops".

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.

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.