A new titanosaur closely related to Lognkosauria from Bajo de la Carpa Formation (Santonian, Upper Cretaceous) of northern Patagonia, Argentina

FILLIPI, L., ; CARBALLIDO, J. L.; JUAREZ VALIERI, R.; PEREZ MORENO, A.

Encuentro; Reunión de Paleovertebrados de la Cuenca Neuquina; 2019

We present a titanosaur sauropod partially excavated from upper section of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous) at La Invernada, Rincón de los Sauces (Neuquén). Recovered material of this specimen (MAU-Pv-LI-626) is composed by three posterior cervical vertebrae; two anterior, and one posterior dorsal vertebra; an anterior caudal vertebrae and a middle caudal centrum. Posterior cervical vertebrae of MAU-Pv-LI-626 share with Lognkosauria titanosaurs Mendozasaurus neguyelap González Riga and Futalognkosaurus dukei Calvo et al., three of the five synapomorphies previously proposed for this clade: laterodorsally expanded cervical neural spines originated by lateral laminae that reach or surpass the wide of the centra, deep and extended spinodiapophyseal fossa in posterior cervical vertebrae and anteriormost caudal vertebrae with neural spines transversely elongated. The preserved anterior dorsal vertebra is similar to that of Mendozasaurus and Futalognkosaurus, with a well-developed prespinal lamina, from the base to nearly the top of neural spine, and without a spinoprezygapophyseal lamina. Anterior dorsals differs from Mendozasaurus and Futalognkosaurus in having a laterodorsally oriented transverse processes. Anterior dorsal vertebrae of MAU-Pv-LI-626 can be differentiated from Mendozasaurus due to the absence of infrapostzygapophyseal fossae and that the spinopostzygapophyseal lamina are straight, forming a triangular contour, that differ to the concave contour present in Mendozasaurus. According to a preliminary cladistic analysis MAU-Pv-LI-626 is recovered as a sister group of Lognkosauria (Mendozasaurus+Futalognkosaurus). Nevertheless, dig of the rest of the specimen, is necessary to confirm its phylogenetic relationships.