New sauropod titanosaur from Cerro Overo-La Invernada (Bajo de la Carpa Formation, Santonian), Upper Cretaceous, northern Patagonia argentina

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

Villa El Chocón

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

Museo Municipal "Ernesto Bachmann"

The outcrops of the Cerro Overo-La Invernada recorded an important diversity of fossil vertebrates including crocodyliforms, turtles, fishes and dinosaurs. Among the dinosaurs, titanosaur sauropods are, along with abelisaurid theropods, the most abundant with one nominated taxon (Overosaurus paradasorum) and, at least, four specimens under study. The new specimen (MAU-Pv-CO-660) presents axial and appendicular elements, highlighting an articulated sector composed by the last three dorsal vertebrae, incomplete sacrum, right ilium, and anterior section of the tail with twelve procoelous vertebrae and associated chevrons. The anterior caudal vertebrae present a neural arch located at the anterior border of the vertebral centrum and prezygapophyses with a strong anterodorsal projection as in Overosaurus and Aeolosaurus. However, the first eight caudal vertebrae, unlike those of Overosaurus and Rinconsaurus, present small lateral fossae on the lateral surface of the vertebral centrum below the transverse process, only observed, although larger in the anterior caudal of Traukutitan. The 9º and 10º caudal vertebrae lack quadrangular centra, and are transversely wide with the ventral surface flat as in Overosaurus. Evidence observed in posterior dorsal and caudal vertebrae would indicate that MAU-Pv-CO-660 correspond to a subadult individual. The histological analysis of appendicular elements shows fibrolamellar bone tissue with primary and secondary osteons, suggesting an overall fast bone growth. These bone tissue and absence of an External Fundamental System indicate that the individual was still growing at the moment of its death. The anatomical features in the caudal vertebrae suggest a new form of titanosaur, closely related to Overosaurus, for this area.