Paleoneuroanatomy of the aetosaur Neoaetosauroides engaeus (Archosauria: Pseudosuchia): First natural and digital endocasts

J.B. DESOJO; M. BELÉN VON BACZKO; J.R.A TABORDA

Albuquerque

Congreso; 78th Annual Meeting of Society of the Vertebrate Paleontology; 2018

SVP

The paleoneuroanatomy of pseudosuchian archosaurs is poorly known, based on direct examination of theinternal morphology of braincases and a few artificial endocasts. Among aetosaurs, only one endocast hasbeen described almost a century ago by Case based on a resin cast, it corresponding to Desmatosuchusspurensis from the Chinle Formation (Norian) of Texas, US. We describe the first natural endocast of anaetosaur, Neoaetosauroides engaeus from the Los Colorados Formation (Norian) of NW Argentina, andalso developed the first digital endocast of this taxon including the encephalon, cranial nerves, inner ear,and middle ear sinuses.This study was based on three skulls referred to Neoaetosauroides engaeus: PULR 108, PVL 5698, andPVL 4363. The neuroanatomy of Neoaetosauroides engaeus exhibits several differences from that ofDesmatosuchus spurensis despite their phylogenetic proximity. The location of the cranial nerves VII,VIII and XII was different between these two species. The olfactory region of Neoaetosauroides engaeushad elongated olfactory tracts and narrow, elliptic bulbs contrasting with the short tracts and widerounded bulbs of Desmatosuchus spurensis, which may be a reflection of their different feeding habits.When orienting the skull on its alert or neutral position, the snout is tilted anteroventrally at 27º from theground and the lateral semicircular canal of the inner ear is anterodorsally inclined at 5º from thehorizontal.This information provided by the endocasts of Neoaetosauroides engaeus about its olfactory region andthe orientation of its head could support an animalivorous diet previously suggested by the biomechanicalstudies of other authors, instead of an herbivorous diet as is inferred for most aetosaurs (e.g.Desmatosuchus spurensis, Stagonolepis robertsoni, Typothorax coccinarum). The new information hereobtained contributes to the knowledge of the neuroanatomical diversity of pseudosuchians and morespecifically among aetosaurs and their paleobiological roles in the Late Triassic continental communities.