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

J.B. DESOJO; M. BELÉN VON BACZKO; LARRY WITMER; GOWER, D; BONA PAULA

Praga

Congreso; Congreso. 12th International Congress of Vertebrate Morphology.; 2019

The paleoneuroanatomy of aetosaurs was previously reported onlyfor Desmatosuchus based on the physical endocast (UMMP 7476)described by Case (1921, J. Comp. Neurol. Neurology 33: 132-147),though new materials of Neoaetosauroides engaeus contributed newknowledge of the encephalon, inner ear, and middle ear sinus. UsingCT-scanning, we developed new digital endocasts of two specimensof D. spurensis, UCMP 27408 and 27410, which provided novel informationabout its inner ear, vasculature, and cranial nerves, enabling usto rectify previous interpretations of some anatomic structures andrecognize interspecific variations within Aetosauria. The systematicassignment of the UCMP specimens was also revised because UCMP27408 was previously referred to D. haplocerus by Small (2002, Zool.J. Linn. Soc.136: 97 ? 111), despite the type material lacking cranialmaterial, so we refer both UCMP 27408 and 27410 to D. spurensisbased on the following characters identified by Parker (2008, PaleoBios,28: 1-40): transversely oriented groove on the parietalsbetween the supratemporal openings, deep median pharyngeal recess,and almost no gap between basal tubera and basipterygoid processes.The new digital endocasts allowed us to reinterpret the exits of cranialnerves (CN) VII, VIII, and XII in the physical endocast UMMP 7476,and confirm the structure of the hypophysis, the passage of the internalcarotid arteries, and CN VI of D. spurensis. The inner ear ofD. spurensis has a marked difference between the anterior and posteriorsemicircular canals and a proportionally long lagena, in contrast tothe short lagena and similarly sized anterior and posterior canals ofN. engaeus. Another difference between these species is that theolfactory tracts are short in D. spurensis and the olfactory bulbs are aswide as long, being more similar to the situation in other herbivorousarchosaurs, than in the animalivorous N. engaeus. Funding: PICT2016-0159 (PB/JBD) & 2014-0609(JBD); NSF IOS-1050154 &1456503 (LMW).