Paleoneuroanatomy: 3D digital endocasts of Desmatosuchus reveal endocranial diversity within Aetosauria (Archosauria: Pseudosuchia)

VON BACZKO, M.B.; BONA, P.; WITMER, L.; DESOJO, J.B.; GOWER, D.

Praga

Congreso; 12th International Congress of Vertebrate Morphology; 2019

University of Washington Friday Harbor Laboratories

The paleoneuroanatomy of aetosaurs from endocranial spaces was previously reported only for Desmatosuchus based on the physical endocast (UMMP 7476) described by Case in 1921, though new material of Neoaetosauroides engaeus also contributed to the knowledge of the encephalon, inner ear, and middle ear sinus of this group. Using CT-scanning, we developed new digital endocasts of two specimens of Desmatosuchus spurensis, UCMP 27408 and 27410, which provide novel information about its inner ear, vasculature, and cranial nerves, enabling us to rectify previous interpretations of some anatomic structures and recognize interspecific variation within Aetosauria. UCMP 27408 was previously referred to D. haplocerus by Small in 2002; however, the type material of this species has no cranial material, so we refer it, together with UCMP 27410 to D. spurensis based on the following cranial characters identified by Parker in 2008: transversely oriented groove on the parietals between the supratemporal openings, deep median pharyngeal recess, and almost no gap between the basal tuber and the basipterygoid processes. The new digital endocasts allowed us to reinterpret the exits of the cranial nerves (CN) VII, VIII, and XII in the physical endocast UMMP 7476, and confirm the presence and location of the hypophysis, and passage of the internal carotid arteries and CN VI of D. spurensis. The inner ear of D. spurensis has a marked difference between the anterior and posterior semicircular canals and a proportionally long lagena, in contrast to the short lagena and similarly sized anterior and posterior semicircular canals of N. engaeus. Another difference between these species is that the olfactory tracts are short and the olfactory bulbs are as wide as long in D. surensis, being more similar to the situation in other herbivorous archosaurs, than in the animalivorous N. engaeus.