New vertebrate remains from the Allen formation (campanian?maastrichtian; upper Cretaceous) in Río Negro, Argentina

CERRONI, M.A.; ROZADILLA, S.; GARCIA MARSA, J.A.; ISASI, M.P.; MOTTA, M.J.; GENTIL, A.; AGNOLÍN, F.L.; NOVAS, F.E.; ARANCIAGA ROLANDO, A.M.; BRISSON EGLI, F.; LIO, G.; D´ANGELO, J.

La Plata

Congreso; Reunion Anual de Comunicaciones de la Asociacion Paleotologica Argentina; 2019

The ?Arriagada fossiliferous site? is located SE from General Roca city, Province of Río Negro, Argentina. In a recent fieldtripto such locality we collected vertebrate remains, including indeterminate Chelidae turtles, and yet innominatehadrosaurids, indeterminate titanosaurids, aeolosaurines, saltasaurines, and abelisaurid dinosaurs. The best representedabelisaurid specimen is represented by incomplete dentary, braincase, right scapulocoracoid and fragments of vertebraeand ribs. The assignation to Abelisauridae is based on a tear-shaped basisphenoidal recess, posterior surface of basioccipitalflattened, and frontals strongly ornamented and dorsoventrally thickened. Fusion of skull elements indicates that the individualwas an adult. It reached approximately 4?5 m in whole length, differing from the almost coeval abelisauridsAbelisaurus and Carnotaurus not only by being smaller in size, but for its morphological features. The new abelisaurid showsbasal tubera dorsoventrally tall, deep and flat surface between the foramen magnum and the supraoccipital crest, doubleforamina for middle cerebral vein, and supratemporal fossa deeply excavated anteriorly. Discoveries in ?Arriagada site? revealsa new species of a mid-sized abelisaurid, but the remaining components of this diverse dinosaur fauna still requiredetailed comparison with materials from other sites of the Allen Formation