Cranial morphology of the late triassic South American archosaur Neoaetosauroides engaeus: Evidence for Aetosaurian diversity

Abstract

The cranial anatomy of Neoaetosauroides engaeus Bonaparte, 1969 from the upper part of the Los Colorados Formation, western Argentina, is addressed herein. This description is based on material collected recently, which permits a complete restoration of the skull; previously, a partial lower jaw and premaxillary and maxillary fragments were the only cranial remains known. Unlike other aetosaurs for which the premaxillary dentition is known, in N.engaeus the upper tooth row extends anteriorly to reach near the expanded tip of the snout; this condition is not compatible with the presence of a keratinous beak previously suggested for other aetosaurs. The conical shape of the teeth of N.engaeus differs from the slightly compressed teeth of Desmatosuchus, Stagonolepis and Typothorax, and the distinctly recurved teeth of Aetosaurus and Aetosauroides. This diversity of dental morphology suggests a variety of food-item preferences among aetosaurs.