INVESTIGADORES
EZCURRA Martin Daniel
congresos y reuniones científicas
Título:
REDESCRIPTION AND PHYLOGENETIC RELATIONSHIPS OF THE PROTEROCHAMPSIAN RHADINOSUCHUS GRACILIS (DIAPSIDA: ARCHOSAURIFORMES) FROM THE EARLY LATE TRIASSIC OF SOUTHERN BRAZIL
Autor/es:
EZCURRA, M. D.; DESOJO, J. B.; RAUHUT, O. W. M.
Lugar:
Cordoba
Reunión:
Jornada; REUNIÓN ANUAL DE COMUNICACIONES DE LA ASOCIACIÓN PALEONTOLÓGICA ARGENTINA; 2013
Resumen:
The proterochampsians are small to medium-sized, quadruped and semi-aquatic reptiles that were part of the evolutionary radiation of Archosauromorpha during the Triassic. The group is restricted to the Middle and Late Triassic of South America with eight nominal species. Rhadinosuchus gracilis was the first described proterochampsian and comes from the late Carnian?earliest Norian of southern Brazil. This species is currently the most enigmatic and poorly known member of the group and, as a result, we redescribe here its anatomy and discuss its phylogenetic relationships. We found that Rhadinosuchus gracilis can be distinguished from other proterochampsians by the presence of, for example, an autapomorphic dentary with a large, anterodorsally opened foramen on its anterior surface. A quantitative phylogenetic analysis found Rhadinosuchus gracilis as more closely related to Gualosuchus reigi and Chanaresuchus bonapartei than to other proterochampsians because of the presence of a maxilla with a distinct longitudinal change in slope between lateral and dorsal surfaces and dorsal surface of nasal and frontal ornamented by ridges radiating from centres of growth. In addition, Rhadinosuchus gracilis was found as the sister taxon of Chanaresuchus bonapartei because of a lacrimal with an antorbital fossa that occupies almost half or more of the anteroposterior length of the ventral process. The topology of the phylogenetic analysis favours multiple dispersal events between the Ischigualasto-Villa Unión (northwestern Argentina) and the Paraná (southern Brazil) basins and there is no current evidence for an endemic radiation of proterochampsians dominated by sympatric cladogenetic events restricted to Brazil or Argentina.