Anatomia comparada e análise filogenética de um anfíbio temnospôndilo do permiano do Rio Grande do Sul

Abstract

Temnospondyls are early amphibians, with a broad morphological and ecological diversity that inhabited the planet between the Carboniferous and Cretaceous. They represent a grade of fossil species, which are very important for evolution of the continental fauna and, possibly, have a strict relationship with current amphibians (Lissamphibia). In Brazil, the group is well represented in Permo–Triassic sediments, with nine species described so far. In Rio Grande do Sul, two species were recorded in Permian sediments from Rio do Rasto Formation, where the material MCP-4275PV was collected. This specimen is represented by a hemimandible preserved in two portions, roughly 50 cm long, indicating that it was a large animal. Preparation of the specimen, with sediment removal, evidenced important characteristics for the diagnose of the specimen in a less inclusive taxonomic level. The morphological analyses suggests that the specimen belong to Capitosauria group and the phylogenetic analysis (TNT, PAUP; 76 terminals, 271 characters) showed that MCP-4275PV is consistently placed within Capitosauria, a group so far exclusively Triassic in distribution. Therefore, the new specimen is the oldest capitosaur and its record points out to a South American origin to the group. Such results bring evidences that according with other studies about possible dispersion routs through Pangaea, from Gondwana to Laurasia and about the radiation and speciation of the group relative to the Permo–Triassic boundary.