Description of the skull, braincase, and dentition of Moschognathus whaitsi (Dinocephalia, Tapinocephalia), and its palaeobiological and behavioral implications.

A subadult Moschognathus whaitsi from the Eastern Cape Province, South Africa, was scanned using synchrotron radiation X-ray computed tomography (SRXCT). Its subadult state allowed the cranial bones and teeth to be identified and individually reconstructed in 3D. A complete description of every preserved cranial bone is here produced, with special attention given to the braincase. An evaluation of a frontal abscess has provided insight into the potential behavior of Moschognathus, regarding the long-standing hypothesis of dinocephalian headbutting. The first 3D description of tapinocephalian dentition shows the unique talon-and-heel tooth morphology and expands our understanding of the replacement patterns in the dentition of basal therapsids. We report evidence of at least three successive replacement generations developing in the incisiform dentition of M. whaitsi simultaneously. The arrangement of these successive generations of replacement incisiform teeth is reminiscent of the complex dental batteries described in sauropod dinosaurs. Furthermore, an alternating pattern of replacement is apparent and suggests that the upper and lower rows of functional teeth were comprised of at least two tooth generations.