was virtually the same. The phylogenetic analysis performed by the team recovered both protoceratopsids as sister taxa, indicating that Bagaceratops and Protoceratops were anatomically and systematically related. Below is the obtained cladogram, showing the position of Protoceratops and Bagaceratops: Evolution Longrich and team in 2010 indicated that highly derived morphology of P. hellenikorhinus—when compared to P. andrewsi—indicates that this species may represent a lineage of Protoceratops that had a longer evolutionary history compared to P. andrewsi, or simply a direct descendant of P. andrewsi. The difference in morphologies between Protoceratops also suggests that the nearby Bayan Mandahu Formation is slightly younger than the Djadokhta Formation. In 2020, Czepiński analyzed several long-undescribed protoceratopsid specimens from the Udyn Sayr and Zamyn Khondt localities of the Djadokhta Formation. One specimen (MPC-D 100/551B) was shown to present skull traits that are intermediate between Bagaceratops rozhdestvenskyi (which is native to adjacent Bayan Mandahu and Barun Goyot) and P. andrewsi. The specimen hails from the Udyn Sayr locality, where Protoceratops remains are dominant, and given the lack of more conclusive anatomical traits, Czepiński assigned the specimen as Bagaceratops sp. He explained that the presence of this Bagaceratops specimen in such unusual locality could be solved by: (1) the coexistence and sympatric (altogether) evolution of both Bagaceratops and Protoceratops at this one locality; (2) the rise of B. rozhdestvenskyi in a different region and eventual migration to Udyn Sayr; (3) hybridization between the two protoceratopsids given the near placement of both Bayan Mandahu and Djadokhta; (4) anagenetic (proggressive evolution) evolutionary transition from P. andrewsi to B. rozhdestvenskyi. Among scenarios, an anagenetic transition was best supported by Czepiński given the fact that no definitive B. rozhdestvenskyi fossils are found in Udyn Sayr, as expected from a hybridization event; MPC-D 100/551B lacks a well-developed accessory antorbital fenestra (hole behind the nostril openings), a trait expected to be present if B. rozhdestvenskyi had migrated to the area; and many specimens of P. andrewsi recovered at Udyn Sayr already feature a decrease in the presence of primitive premaxillary teeth, hence supporting a growing change in the populations. Paleobiology Feeding In 1955 paleontologist Georg Haas examined the overall skull shape of Protoceratops and attempted to reconstruct its jaw musculature. He suggested that the large neck frill was likely an attachment site for masticatory muscles. Such placement of the muscles may have helped to anchor the lower jaws, useful for feeding. Yannicke Dauphin