Megaraptoran remains from Cerro Overo-La Invernada fossil site (Bajo de la Carpa Formation, Santonian), northern Patagonia Argentina

MÉNDEZ, ARIEL H.; PAULINA-CARABAJAL, ARIANA; FILIPPI, LEONARDO S.; GIANECHINI, FEDERICO A.; CRUZADO-CABALLERO, PENÉLOPE; PREVITERA, MARÍA ELENA; BARRIOS, FRANCISCO; SECULI PEREYRA, E. EMANUEL; GARRIDO, ALBERTO C.; PIPO, LAURA

Villa El Chocón

Jornada; III Jornadas de Paleontología de la Cuenca Neuquina; 2021

Museo Municipal "Ernesto Bachmann"

In continental sediments from the Bajo de la Carpa Formation (Upper Cretaceous) at Cerro Overo-La Invernada area (Neuquén Province), a large number of fossil vertebrates remains including turtles, crocodyliforms, and dinosaurs (ornithopods, sauropods, and theropods), have been discovered recently. Among theropods, Abelisauridae have been the only taxonomically confirmed group to date. Here we present remains belonging to a megaraptoran theropod (MAU-Pv-CO-659), consisting in a distal end of the left humerus, the proximal end of the right tibia, and several dorsal and caudal vertebral centra. The distal end of the humerus exhibits a depression on the anterior surface ? above the radial and ulnar condyles ? which is also present (although markedly deeper) in Australovenator, but is absent in Megaraptor. Despite the poor state of preservation of the humerus, the ulnar condyle appears to be greater than the radial condyle in distal view, a condition shared with Australovenator but not with Megaraptor. The development of the tibial cnemial crest is similar to that observed in Aerosteon, being larger than in other megaraptorids such as Australovenator, Fukuiraptor, Murusraptor, Orkoraptor, or Phuwiangvenator. The dorsal vertebral centra have large and deep pneumatic foramina on the lateral surfaces, a distinctive megaraptorid character. The caudal vertebral centra also have pneumatic foramina, less pronounced than those of the dorsal vertebrae, which exhibit an internal septum: a feature only documented in other megaraptorids. This new finding confirms that abelisaurids were not alone as the apex of the food chain in this area of the Neuquén Basin about 85 My ago.