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

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

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2022 vol. 59 p. 1 - 46

0002-7014

merica with some of the largest and smallest sauropod species known to date. Despite its diversity, the evolution of this clade is farfrom being well-known, although some recent analyses have begun to find some consensus in their results. Rinconsauria (defined as the leastinclusive clade containing Rinconsaurusand Muyelensaurus) includes small titanosaurs and is considered as closely related to the lineage ofgiant titanosaurs, Lognkosauria (defined as the least inclusive clade containing Futalognkosaurusand Mendozasaurus), both being part of therecently named clade Colossosauria. The titanosaur Rinconsauruscaudamirus, from the Bajo de la Carpa Formation (Santonian), Río negro,Argentina, is represented by several axial and appendicular elements from at least four specimens. This taxon was only briefly described whenit was named and most of its originally proposed autapomorphies are now recognized as having a more widespread distribution amongsttitanosaurs. Herein we present a detailed osteological description of the axial skeleton and a revised diagnosis for this taxon that firmlyestablishes its validity. Based on comparisons with other titanosaurs, we found three new possible autapomorphies for the axial skeleton ofRinconsaurus, which added to its original combination of characters, endorsing this taxon as a valid genus. Besides, this revision of Rinconsaurusprovides additional osteological data that will contribute to a better resolution of titanosaur phylogeny, contributing at the same time to ourunderstanding of the clade Rinconsauria.