analysis of Protoceratops and its overall morphology, concluded that this taxon represents a ceratopsian more primitive than ceratopsids and not an ankylosaur-ceratopsian ancestor. In 1951 Edwin H. Colbert considered Protoceratops to represent a key ancestor for the ceratopsid lineage, suggesting that it ultimately led to the evolution of large-bodied ceratopsians such as Styracosaurus and Triceratops. Such lineage was suggested to have started from the primitive ceratopsian Psittacosaurus. He also regarded Protoceratops as one of the first "frilled" ceratopsians to appear in the fossil record. However, in 1975 Maryanska and Osmolska argued that it is very unlikely that protoceratopsids evolved from psittacosaurids, and also unlikely that they gave rise to the highly derived (advanced) ceratopsids. The first point was supported by the numerous anatomical differences between protoceratopsids and psittacosaurids, most notably the extreme reduction of some hand digits in the latter group—a trait much less pronounced in protoceratopsids. The second point was explained on the basis of the already derived anatomy in protoceratopsids like Bagaceratops or Protoceratops (such as the jaw morphology). Maryanska and Osmolska also emphasized that some early members of the Ceratopsidae reflect a much older evolutionary history. In 1998, paleontologist Paul Sereno formally defined Protoceratopsidae as the branch-based clade including all coronosaurs closer to Protoceratops than to Triceratops. Furthermore, with the re-examinations of Turanoceratops in 2009 and Zuniceratops—two critical ceratopsian taxa regarding the evolutionary history of ceratopsids—in 2010 it was concluded that the origin of ceratopsids is unrelated to, and older than the fossil record of Protoceratops and relatives. In most recent/modern phylogenetic analyses Protoceratops and Bagaceratops are commonly recovered as sister taxa, leaving the interpretations proposing direct relationships with more derived ceratopsians unsupported. In 2019 Czepiński analyzed a vast majority of referred specimens to the ceratopsians Bagaceratops and Breviceratops, and concluded that most were in fact specimens of the former. Although the genera Gobiceratops, Lamaceratops, Magnirostris, and Platyceratops, were long considered valid and distinct taxa, and sometimes placed within Protoceratopsidae, Czepiński found the diagnostic (identifier) features used to distinguish these taxa to be largely present in Bagaceratops and thus becoming synonyms of this genus. Under this reasoning, Protoceratopsidae consists of Bagaceratops, Breviceratops, and Protoceratops. Below are the proposed relationships among Protoceratopsidae by Czepiński: In 2019 Bitnara Kim and colleagues described a relatively well-preserved Bagaceratops skeleton from the Barun Goyot Formation, noting numerous similarities with Protoceratops. Even though their respective skull anatomy had substantial differences, their postcranial skeleton