Taphofacies analysis of rhynchosaurs from the Late Triassic Maleri Formation, Pranhita-Godavari basin, India, using...

Hyperodapedontine rhynchosaurs, a group of specialized herbivorous archosauromorphs, are restricted to the Late Triassic Lower Maleri Formation of the Pranhita-Godavari (P-G) basin, India and their remains are found mostly within the thick red mudstone unit, calcirudite and mixed mud-sand lithologies. A good number of specimens (~ 210) of these rhynchosaurs, belonging to a minimum of 30 individuals, had been collected historically since 1960s, dominantly from six key accumulation sites near Kothapalle, Bheemini, Narlapuram, Venkatapur, Achlapur and Rampur, Telangana, India. Classical taphonomic studies on these specimens indicated highly fragmentary, transported, weathered and altered bones. This implied significant effects of high energy fluvial transportation on the bones, punctuated by episodes of long subaerial exposures in floodplains. Here, multivariate and spatial statistics have been employed to objectively infer a compact taphonomic framework, conduct a robust taphofacies analysis and precisely reconstruct the palaeoenvironment for the entire rhynchosaur assemblage of the Lower Maleri Formation, P-G basin. Five taphofacies and three taphofacies-lithofacies association (TL1, TL2, TL3) are derived from the combined analyses. TL1 is the dominant association, with a mix of articulated and weathered remains preserved within intercalated parallel-laminated and massive sandstone, indicating considerable transport followed by rapid burial, accompanying the waning of high-energy pulses. TL2 is characterized by fragmented and abraded bones preserved in a finely laminated and stratified mudstone, with occasionally articulated elements, indicating deposition from waning floodwaters in abandoned channel settings. TL3 represents the inter-flood stability phase, where prolonged subaqueous exposure and low sedimentation rates facilitated biological encrustation and early cementation.