Tese
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
Autor
Silva, Lúcio Roberto da
Institución
Resumen
“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.