The cranial anatomy of Tenontosaurus tilletti Ostrom, 1970 (Dinosauria, Ornithopoda)

Abstract

Tenontosaurus tilletti Ostrom, 1970, historically assigned to ‘basal Iguanodontia,’is a species of bipedal herbivore from the Lower Cretaceous (Aptian–Albian). Previous publications on the anatomy of the species have consisted of a cursory account of specimens collected in the Cloverly Formation of the Bighorn Basin of Montana, as well as a more detailed description of the postcranial skeleton by Forster (1990). To date, the skull of T. tilletti remains poorly described due to lack of research and poorly preserved specimens. The present study is an attempt to rectify the situation with m aterial referable to Tenontosaurus tilletti, collected from southeastern Okl ahoma. In particular, an espe- cially well-preserved skull (OMNH 58340) of T. tilletti was CT-scanned and virtually separated into its component elements. These elements, as well as reconstructions of the internal spaces for soft tissues, such as the endocast and cranial nerve foramina, are herein described and illustrated in detail. This descriptio n is used to conduct a novel systematic analysis. The analysis strongly supports the g enus Tenontosaurus, as well as its position relative to ‘hypsilophodonts’ and iguan odontians, and largely agrees with previous analyses