Taphonomy of a late Cretaceous Mammal-bearing microvertebrate assemblage from the Deccan inter-trappean beds of Naskal, peninsular India

Abstract

Taphonomic analysis of a microvertebrate assemblage from the late Cretaceous Deccan inter-trappean sequence of Naskal, peninsular India, is undertaken to infer the taphonomic factors involved in the accumulation of bones at a time predaceous avians and large mammals were non-existent. Approximately 1 ton of matrix was screen washed and a large number (> 9100) of isolated skeletal remains of fish, amphibians, turtles, lizards, snakes, crocodiles, mammals and dinosaurs, in addition to pelecypods, ostracodes, gastropods and charophytes were recovered. Different mechanisms are postulated for the initial accumulation of the fauna. Whereas scavenging activity played no significant role in the accumulations, hydraulic sorting was responsible for accumulation of the terrestrial and semi-aquatic component of the fauna. The wide distribution of bone fragments, presence of pre-burial fractures on some of the bones and the occurrence of the assemblage in a thin, calcareous palaeosol unit indicate that the vertebrate remains accumulated rapidly as a consequence of a prolongedremains of fish, amphibians, turtles, lizards, snakes, crocodiles, mammals and dinosaurs, in addition to pelecypods, ostracodes, gastropods and charophytes were recovered. Different mechanisms are postulated for the initial accumulation of the fauna. Whereas scavenging activity played no significant role in the accumulations, hydraulic sorting was responsible for accumulation of the terrestrial and semi-aquatic component of the fauna. The wide distribution of bone fragments, presence of pre-burial fractures on some of the bones and the occurrence of the assemblage in a thin, calcareous palaeosol unit indicate that the vertebrate remains accumulated rapidly as a consequence of a prolonged, drought-induced, mass mortality event and were subjected to subaerial exposure. The study concludes that the Naskal assemblage accumulated in a distal floodplain lake, which served as a natural death trap, on whose banks terrestrial and other animals might have gathered in search of food and water during a prolonged drought and perished subsequently due to the desiccation of the lake.