Os esfagessaurídeos da Bacia Bauru

Abstract

The Notosuchia was a characteristic and peculiar group in the geological history of the Gondwanic Cretaceous. These crocodylomorphs possessed a very specialized dentition and occurred in several ecological niches. In this context the sphagesaurids present a complex masticatory mechanism adapted for herbivory / omnivory. Four genera have been described for this family: Sphagesaurus, Armadillosuchus, Caipirasuchus and Caryonosuchus, all from the Bauru Basin. This basin is located in south-central South American Platform and consists of Late Cretaceous continental deposits. The descriptions of some sphagesaurids were based on the fragmentary fossils and/or uncompleted preparation; then some morphological characters were incorrectly described. The anatomical reanalysis and the discovery of new specimens allowed the taxonomic revision and annotation of a diagnosis for the family based on the following dental pattern: presence of six sphagesauriform teeth in each maxilla and six on each dentary, each upper tooth with an antagonic tooth in the jaw; premaxilla with a caniniform tooth and another conical tooth posteriorly. Adamantinasuchus possess distinct dentition and chewing mechanism; theses aspects and a phylogenetic analysis exclude it from the family Sphagesauridae. The analysis of new aspects related to chewing on Caipirasuchus corroborated previous proposals for the family, as the proal and unilateral movements of the jaw during the bite. Moreover, it was pointed the function of the diastemata and square-articular joint in the masticatory process. The study of the post-cranium of the Caipirasuchus specimens allowed to estimate that these animals had thin bodies and 1.20 m in length. The analysis of anatomical structures of Sphagesaurus, Caryonosuchus, Armadillosuchus allowed to propose an ecological niche for the Sphagesauridae