Filippi, L.,  Juárez Valieri, R., Gallina, P., Méndez, A., Gianechini, F. y Garrido, A.


Paleontological fieldworks carried out on upper section of the Bajo de la Carpa Formation (Santonian, Upper Cretaceous) at La Invernada area, near  Rincón de los Sauces city (northeast Neuquén Province), result in the discovery of several specimens of derived titanosaurs, belonging to multiple taxa. One of them, consists of an articulated modest-sized individual with a nearly complete skull, the axial sequence from the atlas to the last sacral vertebrae with their respective ribs, and both ilia.This sequence is composed by thirteen cervical, ten dorsal and six sacral vertebrae. The skull displays a spatulate snout morphology, with a straight anterior margin, similar to the morphology previously recognized in other titanosaurs such as Antarctosaurus, Bonitasaura and Brasilotitan. The neurocranial morphology is highly derived compared with other titanosaur taxa with well-known skulls such as Sarmientosaurus, Nemegtosaurus, Tapuiasaurus and Rapetosaurus, with displaced frontals located behind the orbits, resulting in an opposite position to the anterior margin of the snout. The occipital condyle is not preserved, but the location of the neurocranial elements and the atlas-axis complex (found in anatomical position) allow to infer a nearly perpendicular position for the tooth row respect to the cervical sequence. This particular condition, confirmed for first time in a derived titanosaur, is morphologically convergent with derived rebbachisaurids such as Nigersaurus. Besides, their respective biochrons are in agreement with the paleoecological niche replacement of the rebbachisaurids by the spatulate snouted titanosaurs in South America, as previously suggested in the post Turonian faunal turnover.
 
11º Congreso de la Asociación Argentina de Paleontología, Gral. Roca, Río Negro, Argentina 2016.