New digital braincase endocasts of two species of Desmatosuchus and neurocranial diversity within Aetosauria (Archosauria: Pseudosuchia)

M. BELÉN VON BACZKO; DESOJO, JULIA BRENDA; GOWER, D; RIDGELY RYAN; BONA PAULA; LARRY WITMER

ANATOMICAL RECORD-ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2021

1932-8486

In the present contribution we revise, figure, and redescribe several isolatedbraincases of the iconic aetosaur Desmatosuchus from the Placerias Quarrylocality, Chinle Formation, Arizona, United States. The detailed study of theisolated braincases from the UCMP collection allowed us to assign them at thespecies-level and recognize two species of Desmatosuchus for the PlaceriasQuarry: D. spurensis and D. smalli. The former can be distinguished from thelatter by the presence of a transverse sulcus on the parietals, deep median pharyngealrecess on the basisphenoid, almost no gap between the basal tuberaand the basipterygoid processes, and the exoccipitals meeting at the midline.The presence of D. smalli at the Placerias Quarry has not been previouslyreported. Based on the braincases UCMP 27408, 27410, 27407, three new brainendocasts were developed through CT scan images, reconstructing the mostcomplete endocranial casts known for an aetosaur, including the encephalon,cranial nerves, inner ear, and endocranial vasculature. The cranial endocastsalso exhibited some differences between both species of Desmatosuchus, withD. spurensis having a distinguishable dural expansion and markedly asymmetricanterior and posterior semicircular canals of the labyrinth. Additionally,the combination of osteological features and the endocranial casts allowed usto identify and discuss the presence of an ossified orbitosphenoid on theanteriormost region of the braincase among aetosaurs. Furthermore, we wereable to reinterpret some of the observations made by previous authors on theendocast of the holotype of Desmatosuchus spurensis (UMMP VP 7476) andprovide some insight into their neurosensory capabilities.