CONICET | Buscador de Institutos y Recursos Humanos

In this contribution we present a new specimen of rebbachisaurid sauropod from Las Campanas quarry (GPS: 39º16´52,7S/69º01´58,1W), Huincul Formation (late Cenomanian), from Villa El Chocón (Neuquén-Argentina). The new material (MMCH-Pv-49) consist 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 disarticulated ribs. The preservation of the cervico-dorsal transition vertebral series provides improvement in the explanation of the anatomical changes in the lamination of the pectoral series, showing the possible homology of the spinal segment of the spinoprezygapophyseal lamina in the posterior cervical vertebrae. This segment suffers topological modifications that finally leave it in a position where it connects the diapophysis to the neural spine in dorsal vertebrae. In order to resolve the relationships of this new specimen a phylogenetic analysis was carried out, including several diplodocoid taxa. The results show an well-supported but unresolved Rebbachisauridae, that includes Nigersaurus, Limaysaurus, Rebbachisaurus and the new specimen. The later shares with the other well-known 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. No further groups are resolved inside the family. New information is provided about the importance of diplodocoids and particularly rebbachisaurids, in faunal representation for the Aptian-Turonian interval of gondwanan landmasses.

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