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Protoceratopsid
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.〔Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' (Winter 2010 Appendix. )〕 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
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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