Evidence on relation of brain to endocranial cavity in oviraptorid dinosaurs

Brains in living tetrapods other than birds and mammals do not entirely fill the brain cavities. Examination of dinosaur braincases does not usually allow determination relating to how close walls of endocranial cavity lay to the surface of brain. The here described fragment of a skull roof of an oviraptorid dinosaur, Ingenia yanshini, shows perfectly preserved, numerous vascular imprints that cover the internal surfaces of frontals and parietals in the region roofing the cerebral hemispheres and cerebellum. This specimen shows that in oviraptorids the brain closely fitted the brain cavity, to the extent found in birds and mammals. Among dinosaurs, only one similar case has been previously reported in an ornithomimid, Dromiceiomimus brevitertius, but the preserved vascular imprints are less numerous and regular in this dinosaur than in Ingenia yanshini.