Psittacosaurus sibiricus
Alexander O. Averianov, Alexei V. Voronkevich, Sergei V. Leshchinskiy and Alexei V. Fayngertz
Journal of Systematic Palaeontology, Volume 4, Issue 04, December
2006, pp 359-395
Psittacosaurus sibiricus from the Aptian Albian Ilek Formation at
Shestakovo, Kemerovo Province, West Siberia, is represented by two almost complete adult skeletons, several associated groups of bones and numerous isolated bones of individuals ranging from post-hatchling to fully grown animals. Psittacosaurus sibiricus differs from nine other species of the genus by a unique combination of 32 diagnostic characters, six of which are autapomorphies of the species: small infratemporal fenestra, anteroposteriorly short premaxilla, short medial process of postorbital, deep cleft for qaudratojugal on jugal, extending to the posterior side of jugal horn, angular with prominent tuber and 23 presacrals. Psittacosaurus sibiricus is the sister species of P. sinensis, with which it shares the prominent pyramidal
laterally projecting jugal horn, but more derived than the latter in
having more developed palpebral and postorbital horns. The three
lateral foramina on the exoccipital/ opisthotic are interpreted as
exits for cranial nerves X+XI, XII1+2 and XII3, in contrast with
previous interpretations. Cranial nerve IX exits the brain cavity
through the metotic fissure. Most Psittacosaurus localities are
confined to lacustrine deposits and this animal undoubtedly inhabited areas around the great lakes widely distributed in Central Asia during the Early Cretaceous. The age of the Psittacosaurus biochron is estimated as Hauterivian& Albian.
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