Frontal bone pneumatisation in Tragoportax and Miotragocerus (Mammalia, Bovidae) from the Late Miocene of Greece

Bovidae display a distinctive cranial architecture, characterised by multifarious frontal sinuses varying in size and shape. These features are usually considered to be of phylogenetic importance and their functional importance still remains elusive. Pneumatisation is the process in which cranial sinuses result from the resorption and deposition of the bone in response to biomechanical stress. In this study, we use high resolution computed tomography (CT-scanning) to identify these internal cranial structures on 12 bovid cranial specimens from Upper Miocene Greek localities. The present study focuses on two genera, Tragoportax and Miotragocerus, so as to explore the variance inside this group in terms of frontal sinuses. The non-destructive nature of this method allows 3D digital representation of cranial internal features of fossilised material in high resolution, providing also volumetric data of the sinuses. We demonstrate the unique internal morphology that these species possess. This morphology is comprised by wide frontal sinuses conforming closely to the shape of the frontal bone and that extend up to the base of their horn cores. The volume of the sinuses was strongly correlated to the frontal bone size and cranial volume.