Fossildiagenetic characterization of mesosaurid bones (Parareptilia, Mesosauridae): paleoecologic and paleoenvironmental implications

Abstract

Mesosauridae is one of the most antient amniote families secondarily adapted to the aquatic life mode that inhabited the Gondwana supercontinent during the Permian. Their remains are found in correlated strata from Africa and in the South American that, in Brazil, correspond to the Irati Formation. The genus Mesosaurus is mainly found in dark shales, which characterizes deep, poorly oxygenated waters, whereas Stereosternum and Brazilosaurus are found in carbonate, that indicate clear shallow waters. Some studies document the preservation of histological detail of bones and soft tissue, like bone marrow, and some attribute this exceptional preservation to special environmental conditions, like hipersalinity and low oxygen content. Bones, as biomineralized tissues, undergo chemical changes that may reflect several conditions of the depositional environment. In view of this, the goal of this work is to investigate the fossildiagenetic aspects of mesosaurid bones of the Irati Formation and its paleoecological and paleoenvironmental implications. For this purpose, we will use mesosaur samples mostly collected in Angatuba-SP. These will be analyzed under the technics of stereomicroscopy, Scanning Electron Microscopy and Energy Dispersive X-Ray Spectroscopy (SEM/EDS), Energy Dispersive X-Ray Fluorescence (EDXRF), X-Ray Diffraction (XRD), Raman and Infrared spectroscopies. The integration between micromorphology and geochemistry data will provide a broader view on the conditions at the moment of burial, implying correlations of the paleoenvironment, and, possibly, additional information about mesosaur paleoecology. In addition, such geochemical signatures can be contrasted with global events of the Permian.