Um novo espécime de loricata (Archosauria: Pseudosuchia) proveniente da sequência pinheiros-chiniquá (zona de associação de dinodontosaurus), Bacia do Paraná: descrição, taxonomia e considerações filogenéticas

Abstract

“Rauisuchia” is an important group of pseudosuchians widely distributed on the planet during the Meso-Triassic atually except for Antarctica and Australia. This present thesis presents the description and phylogenetic studies of a new specimen belonging to the Rauisuchia collected at the Posto de Gasolina outcrop (Pinheiros-Chiniquá sequence) in Dona Francisca-RS, central region of the Rio Grande do Sul State, Brazil. This new material (ULBRA-PVT-281) is represented by a complete and articulated skull, hyoid apparatus and the following post-cranial elements: cervical column together with respective osteoderms, dorsal and caudal vertebrae, one dorsal osteoderm, dorsal, gastralia, ribs shoulder girdle and a right complete forelimb. The phylogenetical analysis supports ULBRA-PVT-281 as a new specimen of Prestosuchus chiniquensis. The osteological description shows the presence of a quiet defined subnarial foramen between the premaxillar and the maxilla. The phylogenetic significance of this structure was evaluated in Archosauria. In order to do so, a new character was created, relating both shape and position of this structure, modifying a dataset previously published by other authors. The results had shown a new anatomical condition shared between Prestosuchus chiniquensis and Saurosuchus galilei (both from South America), but not recovered as sister taxa. The second paper aims the description of of ULBRA-PVT- 281, and subsequent philogenetical analysis Four methodological approaches were carried out, the first two (with parsimonious algoritmun) did not change the topology previously published for Rauisuchia, in recent papers, so what “Rauisuchia”was not supported as a monophyletic group. The third one (implied weidght) recovered ULBRA-PVT-281 (nested together other P. chiniquensis specimens) as the sister taxon of Saurosuchus galilei, a hypothesis suggested in the first article but not supported in that contribution. In the fourth analysis, we added the constrain of Prestosuchus and Saurosuchus as sister groups, and resulting in a better resolved Archosauria, needing only one more step (1332 steps on 90 MPTs).The results showed that future research efforts should be carried out in order to investigate the close relations between P. chiniquensis and S. galilei, and also to increase our knowledge about these important Triassic predators.