Description of uncommon pneumatic structures of a noasaurid (Theropoda, Dinosauria) cervical vertebra from the Bauru Group (Upper Cretaceous), Brazil

The study of pneumatization along axial series of theropods is mostly based on isolated and fragmented specimens. Among abelisauroids, so far the pneumatization of vertebrae was only recognized by external aspects and the morphology of internal pneumatic structures is restricted to the observation of broken regions. Here we describe and provide μCT-scan of one vertebra recovered from the Adamantina Formation (Campanian-lower Maastrichtian) of the Bauru Group, from Brazil. The specimen (DGM 929-R) comprises a cervical vertebra, which is assigned to Noasauridae based on the anteriorly-placed neural spine and the developed centroprezygapophyseal fossae. The internal structures show regular branching pattern of septae, wide chambers with at least 3 ramifications, and pneumatic pedicles connecting wide, deep fossae of the neural arch, which are indicative of a polycamerate centrum and a procamerate neural arch. Comparisons with other internal structures revealed by tomographic studies and broken regions of cervical series of other theropod specimens show a more diverse arrangement of pneumatic chambers. In addition, a discussion of the internal camerate pneumatic morphology of previously studied theropod cervical vertebrae in the light of the new information revealed by the new material is presented.