Intraspecific variation in the axial skeleton of Aetosauroides scagliai (Archosauria: Aetosauria) and its implications for the aetosaur diversity of the Late Triassic of Brazil

PAES-NETO, VOLTAIRE DUTRA; DESOJO, JULIA BRENDA; BIACCHI BRUST, ANA CAROLINA; CESAR LEANDRO SCHULTZ; DA ROSA ATILA ; SOARES, M. B.

ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS.

ACAD BRASILEIRA DE CIENCIAS

Lugar: Rio de Janeiro; Año: 2021

0001-3765

Aetosauria represents a remarkable clade of armored pseudosuchians inwhich some of its oldest members are recovered from late Carnian units of Brazil.Three species are known: the mid-sized aetosaur Aetosauroides scagliai, which alsooccurs in Argentina, and two small-sized species, Aetobarbakinoides brasiliensis andPolesinesuchus aurelioi. We provide a detailed description and comparative analysisof the axial skeleton of Aetosauroides, identifying some diagnostic features as variable.These include the deep pocket pit lateral to the base of the neural spine, the presenceof the infradiapophyseal laminae and the lateral fossa ventral to the neurocentralsuture. These features are not found in smaller and immature Aetosauroides specimens,resembling the condition found in Polesinesuchus, which is based solely on a juvenileindividual, as revealed by osteoderm microstructure analysis. As Polesinesuchuscannot be anatomically differentiated from other small individuals of Aetosauroides,we propose it as a junior synonym of Aetosauroides scagliai. Our results shrink thenumber of putative ?dwarf? aetosaurs, indicating that morphological variation related toontogeny affects aetosaur taxonomy and phylogeny.