Ariel H. Méndez

The Cervical Vertebrae of the Late Cretaceous Abelisaurid Dinosaur Carnotaurus sastrei

The cervical vertebral series of Carnotaurus sastrei from Argentina is described in detail, and compared with Majungasaurus crenatissimus from Madagascar, both Late Cretaceous (Maastrichtian) in age. Notable differences in the morphology of the cervical vertebrae, especially in the shape and development of the epipophysis and the neural spines, are observed between these two genera. These differences show a neck much more robust in Carnotaurus than in Majungasaurus, may be linked to the evolution of the clade in relation to the divergence time since the two genera shared a common ancestor, and functionally may relate to the feeding function associated to the extreme reduction of the forelimbs.

The caudal vertebral series in abelisaurid dinosaurs

The caudal vertebrae of abelisaurid theropods show notable variations in the shape of the transverse process, among other characters, and these distinguish the two subclasses Brachyrostra and Carnotaurini. The vertebrae in the proximal third of the tail in abelisaurids, especially derived taxa, show adaptations that provide considerable rigidity, when compared to other theropod dinosaurs, especially Maniraptora, which have highly flexible tails. This continues the considerable rigidity in the neck, trunk, and sacral region in abelisaurids, and is consistent with the hypothesis that South American abelisaurids evolved in isolation from those that inhabited India and Madagascar.