Frontal bones of non-avian theropod dinosaurs from the Upper Cretaceous (Santonian–?Campanian) Bostobe Formation of the northeastern Aral Sea region, Kazakhstan

Abstract

Three theropod taxa have been identified based on isolated frontal bones from the Santonian–?Campanian Bostobe Formation at the Shakh-Shakh locality, in the northeastern Aral Sea region of Kazakhstan. A frontal referable to Ornithomimosauria indet. is distinct in having a slightly pronounced cerebral dome. A frontal of an unidentified therizinosaur resembles the element in Erlikosaurus (Cenomanian—Turonian of Mongolia) in most features, but it differs in having an anterolateral prong along the orbital rim, a less-developed facet for contact with the prefrontal, and a larger depression for the cerebral hemisphere. A frontal identifiable as Troodontidae indet. differs from that of Troodon (Campanian—Maastrichtian of North America) and resembles that of the Mongolian Campanian Gobivenator in having a larger supratemporal fossa and the anterior process of the parietals wedged between the frontals. This specimen is the first reliable record for Troodontidae from the Bostobe Formation.