Skull osteology of Aetosauroides scagliai Casamiquela, 1960 (Archosauria: Aetosauria) from the Late Triassic of Brazil: New insights into the paleobiology of aetosaurs.

PAES NETO, V.; DESOJO, JULIA BRENDA; BIACCHI BRUST, ANA CAROLINA; RIBEIRO, A. M.; CESAR LEANDRO SCHULTZE; SOARES, M. B.

PALAEONTOLOGIA ELECTRONICA

COQUINA PRESS

Lugar: New York; Año: 2021 vol. 24

1094-8074

Aetosauroides scagliai, from the Ischigualasto Formation of Argentina and SantaMaria Supersequence of Brazil (Carnian-Norian), is one of the oldest members ofAetosauria, a diverse clade of armored crocodile-line archosaurs. Aetosauroides scagliaidiffers from other aetosaurs in having the maxilla excluded from the margin of theexternal nares, the length/width ratio of the postzygapophyses ≤ 0.75, and other featuresthat place it as one of the earliest-diverging members of the clade. In this paperwe provide a detailed description of the skull of A. scagliai based on a new Brazilianspecimen, revealing that it lacks a pneumatic cavity on the medial surface of the maxillaand further differs from all other known aetosaurs by the presence of ≥ 12 dentaryteeth. However, contra previous studies, the elongated posterior process of the jugaldoes articulate ventrally with the quadratojugal in A. scagliai, forming the posteroventralcorner of the skull as in all other aetosaurs. Aetosauroides scagliai exhibits somecharacters typical of predatory archosaurs (like the recurved ziphodont teeth and mandibulararticulation at the level of the tooth row), but was probably an omnivore, as italso shares several probable adaptations for herbivory with aetosaurs generally (i.e.,edentulous anterior premaxilla and dentary) and stagonolepidoids specifically (e.g.,shovel-shaped snout). This suggests that there was greater trophic diversity in thisclade than usually recognized, at least early in their evolutionary history.