DECODING THE LATE TRIASSIC VERTEBRATE PALEOECOSYSTEM FROM A HIGHLY DIVERSE MULTITAXIC BONEBED

A new metoposaurid-dominated multitaxic mixed bonebed from the Upper Triassic Tiki Formation of India was comprehensively studied. A multi-proxy taphonomic analysis reveals that this bonebed is a parautochthonous, time-averaged, attritional assemblage formed on a floodplain overbank depositional setting. The bonebed has revealed around 31 taxa comprising varied chondrichthyans, dipnoans, actinopterygians, metoposaurids, rhynchosaurs, phytosaurs, several archosauriforms, non-mammalian cynodonts and small dinosaurs. In addition, the bonebed has yielded varied coprolites and unionid bivalves.

The study shows that the Late Triassic Tiki scenario was composed of highly diverse animal communities, which inhabited the terrestrial, semi-aquatic, and aquatic realms. Prey-predator interaction within this paleoecosystem was examined based on numerous bone-bearing coprolites. Based on overall morphology and internal structure, the coprolites have been classified into scroll, spiral, and non-spiral forms. Polarizing and Scanning Electron Microscopy and the elemental analysis reveal that these coprolites contain numerous teeth, ganoid scales, and other skeletal specimens as inclusions within the groundmass. These coprolites are attributed to various types of chondrichthyans, dipnoans, actinopterygians, and other terrestrial tetrapods and highlight a web-like interconnectedness within the Tiki vertebrates, thereby dissolving the inter-realm boundaries. Moreover, the unionids formed an important component of the Tiki aquatic realm and source of food not only for the rich and varied aquatic and semi-aquatic fauna but also for the tetrapods, especially for the rhynchosaurs. Hence, a multifaceted study was carried out to reveal a dynamic and highly diverse vertebrate ecosystem during the Late Triassic of India.