Redescription of a sauropod caudal vertebral series with strong affinities to Rebbachisauridae

LUCAS LERZO; PABLO GALLINA; ALEJANDRO OTERO; JUAN I. CANALE

Congreso; Reunión Virtual de la APA; 2020

Asociación Paleontológica Argentina

The Rebbachisauridae constitutes a group of medium to large sauropods recorded from Lower to Upper Cretaceous rocks (Barremian to Turonian). MMCH Pv-49 includes a partial articulated series of 9 caudal vertebra (five mid-caudal and four associated mid-posterior caudal vertebrae) from the upper levels of Candeleros Formation (Cenomanian) of Villa El Chocón, Neuquén province, Argentina, originally referred to Andesaurus and posteriorly reassigned to Titanosauria indet. With the increased knowledge (both in anatomy and systematic) of Rebbachisauridae in the last 10 years, several caudal characters permitted the re-analysis of this material and a reassessmentto this family, allowing a correlation of this series with the caudal segment 7-15 of Zapalasaurus. Both Zapalasaurus and MMCH PV-49 have amphicoelous centra and robust pedicels of the neural arch located on the anterior half of the centrum. Some characters previous considered as synapomorphies of Titanosauria are now recognized in Rebbachisauridae, such as the presence of neural arch anteriorly located and ventral longitudinal hollow in mid caudal centra. The former is present in mid caudal vertebrae of Demandasaurus, Tataouinea, Nigersaurus, and in MMCH Pv-49. The latter is present in the mid caudal vertebra of Comahuesaurus, Demandasaurus, Tataouinea (with the particularity of bearing deep fossae in the ventral surface), and MMCH Pv49. These features, plus new evidence from unpublished rebbachisaurid materials from the Candeleros Formation, strongly support the rebbachisaurid affinities of MMCH Pv-49 as well as contribute to the ingroup relationships.