New Data on Skull Morphology of Psittacosaurus sibiricus (Dinosauria: Ceratopsia) Using Micro-Computed Tomography.

The morphology of the skull and endocranium of juvenile and adult specimens of the basal ceratopsian dinosaur P. sibiricus from the Lower Cretaceous Ilek formation (Kemerovo oblast-Kuzbass, Western Siberia, Russia) is described using micro-computed tomography scans and three-dimensional modelling. The diagnostic cranial characters of P. sibiricus include premaxilla-rostral canal present, maxillary fossa and maxillary protuberance absent, ten maxillary teeth in adults, maxillary-lacrimal contact, postorbital horn composed of the postorbital and the jugal present, large ventrolaterally projecting pyramidal jugal horns, deeply bifurcating jugal posterior process, external mandibular fenestra absent, dentary flange lacks the anterior corner but has a prominent posterior angle extending on the angular, and angular tuber projecting laterally at the posterior end of the ventral flange. [ABSTRACT FROM AUTHOR]