REDISCOVERED CRANIAL MATERIAL OF VENATICOSUCHUS RUSCONII ALLOWS THE FIRST JAW BIOMECHANICS IN ORNITHOSUCHIDAE (ARCHOSAURIA: PSEUDOSUCHIA) -- Preprint doi:10.5710/AMGH.19.03.2018.3170

María B. Von Baczko

Abstract


During the Triassic period, pseudosuchians had a wider variety of feeding habits than those seen nowadays, including herbivorous, omnivorous, as well as carnivorous diets. Ornithosuchids have been historically proposed as either hunters or scavengers based on their general anatomy. The rediscovered cranial materials of the ornithosuchid Venaticosuchus described here in detail which allowed the reconstruction of its jaw musculature and a geometric biomechanic analysis was carried out to study the possible feeding habits of ornithosuchids. The muscles were reconstructed based on inferences of their osteological correlates seen in their closest living relatives such as Caiman, Alligator, and Iguana. Consequently, the jaws were considered as a third class lever system and the moment arms were calculated for the adductor and depressor musculature. The study of the three species of ornithosuchids (Ornithosuchus, Venaticosuchus, and Riojasuchus) revealed greater similarities between ornithosuchids and aetosaurs, despite having different feeding habits, than between ornithosuchids and crocodylians. The relative bite force of Venaticosuchus resulted higher than that of other ornithosuchids, aetosaurs and Alligator. The elevated bite force identified for ornithosuchids plus their low bite speed and the morphology of their constricted snouts suggest features more compatible to scavenging feeding habits. Ornithosuchids were not the apex predators of the Late Triassic continental communities but were more likely regarded to scavenging or preyed on small animals such as procolophonids, sphenodontians, juvenile aetosaurs, erpetosuchids, cinodonts, and dicynodonts that did not exceed them in size.

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