Protoceratopsid

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

Protoceratopsidae is a family within the group Ceratopsia.^[1] The name Protoceratopsid is derived from Greek for "first horned face". Protoceratopsids have so far been found exclusively in the Late Cretaceous, dating to between about 99.6 and 70.6 million years ago.^[2] Although Ceratopsians have been found all over the world, Protoceratopsids lived only in Asia with most specimens found in China and the Nemegt Basin in Mongolia. ^[1] Like most Ceratopsians, Protoceratopsids were herbivorous, with blocks of teeth made for grinding that were constantly being replaced and a hooked beak for grabbing plants.^[3] Protoceratopsids were relatively small, between 1-2.5 m in length from head to tail. ^[4] Their bony frill and horns were much smaller than the related Ceratopsids.^[5] Protoceratopsids were likely slow runners and tended to move at a walk or a trot.^[4] Their legs may have been vertical, but there are some theories that they were splayed out to the side, contributing to their slowness.^[3] There is evidence that Protoceratops formed aggregations. Specimens of juveniles and young adults are often found in groups, although adults tend to be solitary. The nature of these groups is not completely known, though herds of young likely formed for protection from predators, and adults are believed to have come together for communal nesting.^[6]

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''s 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

1. Naish, Darren (February 2013). "New perspectives on horned dinosaurs: the Royal Tyrrell Museum Ceratopsian Symposium.". Historical Biology 25 (1): 121–124. doi:10.1080/08912963.2012.688589.
2. Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
3. Fastovsky, David; Weishampel, David (2009). Dinosaurs A Concise Natural History. New York: Cambridge University Press. pp. 118–133. ISBN 978-0-521-71902-5.
4. Tereschenko, V (2008). "Adaptive Features of Protoceratopoids (Ornithischia: Neoceratopsia)". Paleontological Journal 42 (3): 50–64. doi:10.1134/S003103010803009X.
5. Maiorino, Leonardo; Farke, Andrew A.; Kotsakis, Tassos; Piras, Paolo (7 May 2015). "Males Resemble Females: Re-Evaluating Sexual Dimorphism in Protoceratops andrewsi (Neoceratopsia, Protoceratopsidae)". PLOS ONE. pp. e0126464. doi:10.1371/journal.pone.0126464. Retrieved 30 April 2016.
6. Hone, David W. E.; Farke, Andrew A.; Watabe, Mahito; Shigeru, Suzuki; Tsogtbaatar, Khishigjav (26 November 2014). "A New Mass Mortality of Juvenile Protoceratops and Size-Segregated Aggregation Behaviour in Juvenile Non-Avian Dinosaurs". PLOS ONE. pp. e113306. doi:10.1371/journal.pone.0113306. Retrieved 30 April 2016.

• 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.