New abelisauroid remains from the huincul formation (cenomanian-turonian; upper Cretaceous), Río Negro province, Argentina

AGNOLÍN, F.L.; NOVAS, F.E.; MOTTA, M.J.; BRISSON EGLI, F.; CERRONI, M.A.; ARANCIAGA ROLANDO, A.M.

Congreso; Jornadas Argentinas de Paleontología de Vertebrados XXXIII; 2019

The Violante Farm is a fossiliferous site located at northwestern Río Negro province,Patagonia, Argentina. In this locality, the Huincul Formation (Neuquén Group,Cenomanian-Turonian, Upper Cretaceous) is widely exposed. In a recent fieldworkcarried out in the area, several bones of small theropods of abelisauroid affinities wererecovered. They are represented by two specimens: 1) associated maxilla, dorsal, sacraland caudal vertebrae, and pubis, and 2) a partial tail and pedal elements. The latterspecimen shows caudal vertebrae with abelisauroid features, including vertebrae with aflat and wide area lateral to the neural spines and dorsally oriented transverse processes.In contrast to abelisaurids, the processes are relatively narrow, without anterior orposterior projections. Some caudal vertebrae show parallelogram centra in lateral view,indicating a pronounced tail curvature. The other specimen shows a maxilla very similarto that of abelisaurids, being short and tall, with a slit-like promaxillary fenestra, curvedgrooves on its lateral surface, and a dorsoventrally expanded maxillary body thatresembles that of Skorpiovenator Canale et al. 2008. However, the ascending process isanterodorsally oriented, and the antorbital fossa is particularly extended along the dorsal portion of the horizontal ramus; characters that are absent in other abelisaurids and mayrepresent autapomorphies of this taxon. These new specimens, likely adults due thefusion of centra and neural arches, indicate that small-sized abelisauroids were probablymore diverse than previously thought.