New vertebrate remains from the Allen Formation (Campanian?Maastrichtian; Upper Cretaceous) in Río Negro, Argentina

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

La Plata

Otro; RCAPA; 2019

Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata (UNLP)

The ?Arriagada fossiliferous site? is located SE from General Roca city, Province of Río Negro,Argentina. In a recent fieldtrip to such locality we collected vertebrate remains, includingindeterminate Chelidae turtles, and yet innominate hadrosaurids, indeterminate titanosaurids,aeolosaurines, saltasaurines, and abelisaurid dinosaurs. The best represented abelisauridspecimen is represented by incomplete dentary, braincase, right scapulocoracoid and fragments ofvertebrae and ribs. The assignation to Abelisauridae is based on a tear-shaped basisphenoidal recess, posterior surface of basioccipital flattened, and frontals strongly ornamented anddorsoventrally thickened. Fusion of skull elements indicates that the individual was an adult. Itreached 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 shows basal tubera dorsoventrally tall, deep and flat surface between theforamen magnum and the supraoccipital crest, double foramina for middle cerebral vein, andsupratemporal fossa deeply excavated anteriorly. Discoveries in ?Arriagada site? reveals a newspecies of a mid-sized abelisaurid, but the remaining components of this diverse dinosaur faunastill require detailed comparison with materials from other sites of the Allen Formation.*Project supported by the National Geographic Society, Grant CP050ER17 (to A.M.A.R.).