A REAPPRAISAL OF THE BASAL ARCHOSAUROMORPH TASMANIOSAURUS TRIASSICUS FROM THE LOWER TRIASSIC OF TASMANIA (AUSTRALIA) AND THE PRESENCE OF THE VOMERO-NASAL ORGANS IN ARCHOSAURS

EZCURRA, M. D.

Cordoba

Jornada; REUNIÓN ANUAL DE COMUNICACIONES DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA; 2013

Proterosuchidae are the most taxonomically diverse terrestrial diapsids sampled in the immediate aftermath of the Permo-Triassic mass extinction. They are currently known from South Africa, China, Russia, Australia and India and the taxonomic content of the group is currently in a state of flux because of a poor anatomic and systematic understanding. The anatomy and taxonomy of the putative proterosuchid Tasmaniosaurus triassicus from the Lower Triassic of Hobart, Tasmania (Australia), is revisited here. The holotype and currently only known specimen includes cranial and postcranial remains. Several bones of the skull roof, lower jaw and hindlimb are re-identified or reinterpreted, contrasting with the descriptions of previous authors. The new information provided here shows that Tasmaniosaurus closely resembles the South African proterosuchid Proterosuchus, but it differed in the presence of, for example, a slightly downturned premaxilla, a shorter anterior process of maxilla, and a diamond-shaped anterior end of interclavicle. Previous claims for the presence of gut contents in the holotype of Tasmaniosaurus are considered ambiguous. The description of the cranial endocast of Tasmaniosaurus provides for the first time information about the anatomy of this region in proterosuchids. The cranial endocast preserves possibly part of the vomero-nasal (= Jacobson?s) system laterally to the olfactory bulbs. Previous claims of the absence of the vomero-nasal organs in archosaurs, which is suggested by the extant phylogenetic bracket, are questioned because its absence in both clades of extant archosaurs seems to be directly related with the independent acquisition of a non-ground living mode of life.