New rebbachisaurid remains (Dinosauria: Sauropoda) from the Late Cretaceous of Neuquén Province, Argentina.

HALUZA, ALEJANDRO; CANALE, JUAN IGNACIO; OTERO, ALEJANDRO; PÉREZ, LEANDRO MARTÍN

San Rafael, Provincia de Mendoza, Argentina

Jornada; XXIV Jornadas Argentinas de Paleontología de Vertebrados; 2009

In this contribution we present a new specimen of rebbachisaurid sauropod from Las Campanas quarry, Huincul Formation (late Cenomanian), from Villa El Chocón (Neuquén, Argentina). The new material (MMCH-Pv-49) consists in a partially articulated skeleton including: seven articulated cervical vertebrae, four articulated anterior dorsal vertebrae, six disarticulated mid-posterior dorsal vertebrae, a right scapula, a right humerus, and some articulated and ribs. The cervico-dorsal vertebral series provides a possible explanation of the homology of the “spinal segment” of the spinoprezygapophyseal lamina in posterior cervical vertebrae with the spinodiapophyseal lamina of the dorsal vertebrae. In order to resolve the relationships of this new specimen a phylogenetic analysis was carried out, including several diplodocoid taxa (9 ingroup taxa, 2 outgroup taxa, 162 chars, CI=92, RI=93). The results show a well-supported but unresolved Rebbachisauridae (decay index=5) showing Nigersaurus Sereno et. al.; as the most basal member and a tricotomy (decay index=3) that includes Limaysaurus Salgado et al.; Rebbachisaurus Lavocat; and the new specimen. The later differs from Limaysaurus in the absence of the accessory spinopostzygapophyseal lamina in cervical vertebrae and from Rebbachisaurus in the absence of posterior centroparapophyseal lamina in dorsal vertebrae. The new materials share with the other rebbachisaurids four synapomorphies of the family: 1) “petal-shaped” posterior dorsal neural spines, 2) hyposphene-hypantrum articulations absent, 3) “racquet-shaped” scapular blade and 4) presence of a “hook-like” acromion process. New information is provided about the importance of diplodocoids and particularly rebbachisaurids in faunal representation for the Aptian-Turonian interval of gondwanan landmasses.