A Ceratopsian dinosaurPsittacosaurus sibiricusfrom the Early Cretaceous of West Siberia, Russia and its phylogenetic relationships

Synopsis 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...