A natural cranial endocast with possible dicraeosaurid (Sauropoda, Diplodocoidea) affinities from the Lower Cretaceous of Patagonia

Abstract

A partially preserved sauropod natural cranial endocast (MLL-003) was collected from the Lower Cretaceous Mulichinco Formation in Argentina. The cast consists of cemented sandstone that has preserved in detail the general endocranial morphology, but not the cranial nerves. The dural expansion, the dorsal portion of the medulla oblongata, the cerebrum and the optic lobes are preserved, and suggest the specimen belongs to a sauropod dinosaur. The presence of the pineal foramen, and possibly post-parietal foramen and floccular process, suggests this specimen is more likely related to dicraeosaurids than it is to Titanosauriformes. This makes specimen MLL-003 particularly relevant because the paleoneurology of Dicraeosauridae is poorly known.