On the skull of Massospondylus carinatus Owen, 1854 (Dinosauria: Sauropodomorpha) from the Elliot and Clarens formations (Lower Jurassic) of South Africa

Abstract

This paper presents a comprehensive description of the cranial structure of the sauropodomorph dinosaur Massospondylus carinatus, based on four well-preserved skulls (including one of a juvenile individual) from the Lower Jurassic Elliot and Clarens formations of South Africa. Massospondylus can be distinguished from other basal sauropodomorph dinosaurs by the following combination of primitive and derived cranial character-states: The greatest transverse width of the skull exceeds its dorsoventral height by at least 10 percent. Even in adult specimens, the orbit is proportionately large and the antorbital region proportionately short. The maxilla has a tall, nearly vertical dorsal process, and its medial sheet is narrow anteroposteriorly. A long posterior process of the prefrontal extends along the dorsal margin of the orbit, but the frontal still participates significantly in the formation of the orbital margin. There is a distinct ridge on the dorsolateral aspect of the lacrimal and a knob on the lateral surface of the prefrontal. A partial skull from the Lower Jurassic Kayenta Formation of Arizona previously attributed to Massospondylus differs from the South African material in several cranial and dental features and is not referable to this taxon.