A new articulated eutitanosaur from Northern Patagonia, Argentina.

GONZÁLEZ RIGA, BERNARDO J.; CALVO, JORGE O.; PORFIRI, JUAN

Buzios, Brasil

Congreso; XX Congresso Brasileiro de Paleontologia; 2007

Comissao Organizadora do XX Congresso Brasileiro de Paleontologia

Most titanosaur dinosaurs are represented by incomplete skeletal elements. In this context, the discovery of a well preserved specimen from the Late Campanian-Early Maastrichtian strata of the Neuquén Province (Argentina) provides new evidences from systematic and phylogenetic viewpoints. The fossil was recovered at La Invernada site, in levels of the Allen Formation (Malargue Group, Neuquén basin). It is composed by a partial and articulated skeleton (~ 8 m length) that includes the caudal series, the left fore- and hindlimbs, and the sacral and dorsal ribs. This specimen is considered as a derived eutitanosaur characterized by strongly procoelous caudal vertebrae and relatively slender appendicular bones. The neural spines in most caudal vertebrae are missing. The caudal centra are relatively short in comparison with other eutitanosaurs from the Late Cretaceous of South America (e.g. Baurutitan Kellner, Campos and Trotta; Pellegrinisaurus Salgado. This specimen is excluded from Saltasaurinae clade by the absence of strongly depressed anterior and middle caudal centra as well as the absence of anteroposteriorly elongated depression divided by a sagittal crest on the ventral surface of the centra as in Pellegrinisaurus. This specimen shares with Rinconsaurus Calvo and González Riga, and Aeolosaurus Powell, the general morphology of appendicular bones, specially the structure of the ischium, that is characterized by a slender and well developed iliac pedicel. The appendicular remains also include five articulated metacarpals without distal articular faces. Moreover it preserves a complete left forelimb including the third titanosaur articulated pes known in the world. The pes shows a phalangeal formula of 2-2-2-2-0 and the first three digits possesses sickle-shaped claws. The discovery of this specimen, probably a new species, gives us detailed information on appendicular morphology of non-saltasaurinae eutitanosaurs that inhabited the Patagonia during the latest Cretaceous.     Study supported by Proyecto Dino, Wintershall Company, IANIGLA-CRICYT, CONICET (PIP-5222), Universidad Nacional del Comahue (Project I -122) and Universidad Nacional de Cuyo.