BRAINCASE AND ENDOCRANIAL ANATOMY OF CRYOLOPHOSAURUS ELLIOTI (DINOSAURIA: THEROPODA) FROM THE EARLY JURASSIC OF ANTARCTICA

Cryolophosaurus ellioti, a theropod dinosaur discovered in 1991, represents both the most complete dinosaur skeleton from Antarctica and the largest theropod from the Early Jurassic. Previous studies of the anatomy of Cryolophosaurus have focused on the postcranial anatomy and the bony aspects of the skull (Smith et al., 2007). No research has hitherto been conducted on the soft tissue anatomy of the brain. The holotype skull contains a nearly complete and undistorted cranial cavity, roughly approximating the shape and size of the living brain. Through the use of noninvasive CT scanning methods, we have created a digital endocast, which forms the basis of this study. This research provides a detailed comparative anatomical description of the braincase and endocranial anatomy of Cryolophosaurus, including the position of the cranial nerves, the angles of the pontine and cephalic flexures, and relative position of the major lobes. These data allow us, for the first time, to estimate the intelligence of Cryolophosaurus through calculations of encephalization quotient. Additionally, the introduction of phylogenetically informative endocast features clarifies the position of Cryolophosaurus within the theropod evolutionary tree; the dissimilarity of the endocast of Cryolophosaurus to those of Allosauroids and Coelurosaurs suggests that Cryolophosaurus occupies the basal position in Theropoda hypothesized by Smith et al. (2007). Thus, this research reveals new behavioral, paleobiological, and phylogenetic insights of Cryolophosaurus, with implications for the rest of Theropoda.