Evidence of bacterial decay and early diagenesis in a partially articulated tetrapod from the triassic chañares formation

Abstract

The vertebrate fauna from the lower Carnian Chañares Formation of Argentina is dominated by well-preserved small- and medium-bodied archosauriforms and therapsids. Here we report the discovery of a non-mammalian therapsid dicynodont (of greater than 20 cm skull length) that was found partially articulated within the floodplain deposit. Taphonomic analysis of this specimen reveals details of its paleobiology and taphonomic history, including the cause of death, exposure to predation and/or scavenging, subsequent subaerial decay, and final entombment. The specimen studied also allowed for the documentation of the activity of micro-organisms involved in decay processes during the biostratinomic stage (soft tissue decomposition on surface) and diagenetic stages (anaerobic decay). Our results indicate that despite bones being found in concretions the formation of calcareous concretions is not required for bone preservation. Consequently, this study highlights the role of volcanic ash in promoting bone preservation.