Rediagnosis of Rinconsaurus caudamirus Calvo and González Riga (Dinosauria, Sauropoda) from the Anacleto Formation (Upper Cretaceous: Campanian) of Rincón de los Sauces (Neuquén, Argentina)

PÉREZ MORENO, A.; CARBALLIDO, J. L.; OTERO, A.; SALGADO, L.; CALVO, J. O.; FILLIPI, L.,

Congreso; Congreso de Comunicaciones de la Asociación Paleontológica Argentina; 2018

Despite its great diversity, knowledge of many aspects of titanosaur sauropod anatomy is relatively poor, in part due to the fragmentary nature of many species. Rinconsaurus caudamirus, is represented by several partial skeletons from a single locality from the Anacleto Formation (Upper Cretaceous, Campanian), in the north of Neuquén Province, Argentina. Since its original description, this taxon has not been subjected to an exhaustive revision, which has raised a number of questions about its taxonomical status. Among them, stand out the fact that characters 1 and 2 from the three originally used for diagnosing it showed to be more widespread distributed among Titanosauria. Additionally, an important morphological variability is observed among caudal vertebrae, making necessary the revision of the assemblage originally stated out. Here we present a revision of the postcranial material of Rinconsaurus based on new observations and comparisons with related taxa. The observed morphological differences in caudal vertebrae could be well explained as the product of different ontogenetic stages and serial variations, whereas three new autapomorphic character were detected (1-posterior cervicals with the ventral end of the spinoprezygapohyseal lamina intercepting the intraprezygapophyseal lamina; 2-anteriormost caudals with two marked lateral faces with the lower face strongly constricted ventrally; 3-caudal vertebrae with the anterior articular surface markedly higher than the posterior). Therefore, based on the present study we sustain the monospecific interpretation of the assemblage and reinforce the status of Rinconsaurus caudamirus as a valid species.