New rebbachisaurid (Sauropoda, Diplodocoidea) skull remains from Candeleros Formation (Cenomanian), Neuquen Province, Argentina.

PAULINA CARABAJAL, A.; HALUZA, A.; CANALE, J.I.

La Rioja

Jornada; XXVII Jornadas Argentinas de Paleontología de Vertebrados; 2013

Rebbachisaurid remains are frequently recorded in the basalmost units of Neuquéen Group. However, skull remains are scarce and particularlythe braincase anatomy of the Argentinean taxa is poorly known. Here we report a new rebbachisaurid partial braincase and aright quadrate (MMCH-PV 63) recovered from the Candeleros Formation. The braincase is fractured sagitally allowing observation of theendocranial cavity. Latex endocasts of the braincase and inner ear were made. The braincase exhibits some traits similar to Nigersaurus andLimaysaurus, such as the strongly convex orbitary vault of frontal, the low and laterally compressed crista antotica, and the size and distributionof the cranial foramina. The large orbitocerebral foramen observed in Nigersaurus is absent in Limaysaurus and the new specimen. As inother sauropods, the brain is anteroposteriorly short and laterally expanded. The olfactory tract is short and wide, and projected anteriorly asin Nigersaurus, rather than anterodorsally as in Diplodocus and Camarasaurus. The cerebral hemispheres are rounded and laterally expanded,visible in dorsal view as in Nigersaurus. In other diplodocoids (i.e., Diplodocus, Amargasaurus) the dorsal expansion is large, obscuring thedorsal morphology of the brain. The new specimen is noteworthy for the presence of a small floccular process, only known in Nigersaurus andthe basal titanosauriform Giraffatitan within sauropods. The pituitary body is strongly projected posteroventrally as in Nigersaurus. Cranialnerve VI penetrates the pituitary fossa, as in other diplodocoids. The morphology of the inner ear strongly resembles that of Nigersaurus, asdoes the dorsal orientation of the lateral semicircular canal. Comparisons with the braincase of Limaysaurus will improve our knowledge onthe paleoneurology of Limaysaurinae. Furthermore, the identification of characteristic braincase traits of the clade has could be potentiallyuseful in phylogeny.