CONICET | Buscador de Institutos y Recursos Humanos

The function of the jaw apparatus and the possible dietary habits of the aetosaur Neoaetosauroides engaeus from the Triassic of South America was analyzed in comparison with Northern Hemisphere aetosaurs Desmatosuchus haplocerus and Stagonalepis robertsoni and the living short-snouted crocodile Alligator mississippiensis. The adductor and depressor jaw musculature of these was reconstructed based on dental and skeletal comparisons with living closest relatives (EPB), followed by the analysis of the moment arms of these muscles to infer feeding habits. The aetosaurian skull design indicates that the total leverage of the inferred jaw musculature provides force rather than speed. However, within aetosaurs, the high ratios of muscle moment arms to bite moments indicate stronger bites in the northern Hemisphere forms, and faster ones in Neoaetosauroides. These differences indicate more developed crushing, chopping, and slicing capacities, especially at the back of the tooth series for D. haplocerus and S. robertsoni; while it opens a window to consider different abilities in which speed is involved for N. engaeus. There are differences among aetosaurs in dental characters, position of the supratemporal fenestra, location of the jaw joint relative to the tooth row, and shape of the lower jaw. Neoaetosauroides does not show evidence of dental serrations and wear facets, probably consistent with a relatively soft and non-abrasive diet, such as soft leaves and/or larvae and insects without hard structures. It might be possible that Neoaetosauroides represents a tendency towards insectivorous feeding habits, exploiting a food source that was widespread in continental environments throughout the Triassic.