DID LATE CRETACEOUS HYPSODONT GONDWANATHERIAN MAMMALS COEXIST WITH GRASSES?: PHYTOLITH RECORDS FROM THE INTERTRAPPEAN NASKAL LOCALITY, CENTRAL INDIA

Gondwanatherian mammals with extremely high-crowned (hypsodont) cheek teeth inhabited India during the latest Cretaceous (67-66 Ma). Hypsodonty in modern herbivorous mammals is typically associated with life in open, grass-dominated habitats, but because it was previously thought that grasses had not evolved by the Late Cretaceous, gondwanatherians were assumed to have acquired their derived tooth morphology as an adaptation to a semi-aquatic or burrowing habit. Recently described, sparse microscopic silica bodies from grasses (phytoliths) in titanosaur dinosaur coprolites and sediments from several Deccan inter- and infratrappean beds in Central India have suggested that grasses were part of Late Cretaceous vegetation on the Indian subcontinent. This has opened up the possibility that the evolution of high-crowned cheek teeth in sudamericid gondwanatherian mammals was linked to a diet based on grass. However, no studies have attempted to directly investigate whether these gondwanatherians co-occurred with grasses. We sampled sediment at high-resolution at one of the classic latest Cretaceous intertrappean sites from which sudamericid gondwanatherians have been collected, Naskal, Andhra Pradesh, Central India. The sediments at Naskal represent deposition in fluvial or lacustrine environments, overprinted by paleosol formation, likely in a semi-arid environment. The relatively well-preserved phytolith assemblages extracted from these samples contain a mixture of forest indicators and diverse grass phytoliths, indicating that grasses made up a moderate component of the vegetation, or at least the phytolith producing vegetation. Future work will continue testing the causal link between gondwanatherian mammals and grasses by investigating paleovegetation at other Late Cretaceous mammal-bearing sites in India.