An Abelisaurid Humerus from the Bajo de la Carpa Formation (Upper Cretaceous, Santonian), Northern Patagonia, with Comments on Morphological Aspects of the Humerus in Abelisauridae

The Cerro Overo-La Invernada rea (Bajo de la Carpa Formation, Upper Cretaceous, Santonian) in northern Patagonia has yielded abundant fossils of abelisaurid theropods, including cranial, vertebral, pectoral and pelvic remains.However, forelimb bones were unknown.Here, we describe a humerus that exhibits distinctive features that allow its assignment to Abelisauridae, for example, flattened distal condyles, greater tubercle distally located, and humeral head subspherical in proximal view.It also exhibits a noticeable torsion of the distal end.Morphofunctional analysis indicates a substantial capacity for protraction along with a limited capacity for lateromedial movement.In a general aspect, MAU-PV-LI-737 is morphologically intermediate between the more gracile humerus of noasaurids and the robust shape observed in Campanian-Maastrichtian abelisaurid forms.