THE AXIAL SKELETON OF RINCONSAURUS CAUDAMIRUS>/em> (SAUROPODA: TITANOSAURIA) FROM THE LATE CRETACEOUS OF PATAGONIA, ARGENTINA

AGUSTÍN PÉREZ MORENO; CARBALLIDO, JOSÉ L.; ALEJANDRO OTERO; LEONARDO SALGADO; JORGE CALVO

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2021

0002-7014

The titanosaur Rinconsaurus caudamirus, from the Bajo de la Carpa Formation (Santonian), Río Negro, Argentina, is represented by several axial and appendicular elements from, at least, four specimens. The axial skeleton of this taxon was exhaustive described in previous works; however, a complete description of its appendicular skeleton and a phylogenetic analysis was pendant. This paper focuses on the description of the appendicular skeleton of Rinconsaurus and its kinship relationships. Comparison with other titanosaurs in the region confirms that Rinconsaurus clearly differs from them and stands out for the presence of a combination of characters seen in lognkosaurid, aeolosaurid and saltasaurid titanosaurs and for the presence of a scapula morphotype seen alone in Bellusaurus, Dreadnougthus and Muyelensaurus, which is characterized by having an orientation of the scapular blade relative to the coracoid articulation oblique with an angle of approximately 66 °. Equations for predicting body mass in sauropods suggest a body mass of at least 3-5 tonnes for the largest individuals of Rinconsaurus caudamirus, being slenderer than saltasaurines, but heavier than aeolosaurids. The comprehensive study of the postcranial skeleton supports the hypothesis that Rinconsaurus caudamirus is the earliest branched representative of the Rinconsauria clade, with the Aeolosaurini being the most derived clade within it. In turn, Rinconsauria would be a separate lineage within the great clade Lognkosauria.