GASTROPOD DRILLING PREDATION IN THE UPPER JURASSIC OF KUTCH, INDIA

Abstract: Gastropod drillholes on prey shells provide an opportunity to test the importance of predation in an evolutionary context. Although records of drilling predation are widespread across the Phanerozoic, the temporal distribution and relative importance of this mode of predation is still controversial. Further, some studies indicate a decline of drilling predation in the Mesozoic but other studies do not. In this study, we present a new dataset of gastropod drilling predation on Kimmeridgian and Tithonian bivalves of Kutch, India. Our study suggests that drilling was one of the prevailing modes of predation in the Upper Jurassic of Kutch with strongly variable intensities, ranging from 2% in the Kimmeridgian Seebachia to 26% in the Tithonian Pinna. A significant, albeit small, increase in drilling intensity from the Kimmeridgian to the Tithonian assemblages is associated with a change in relative sea-level and depositional environment. The morphology of drillholes and recent discovery of body fossils from the same stratigraphic units suggest naticid gastropods as the most likely drillers. A literature survey, along with previously collected specimen from the Jurassic of Kutch, reveals a more complex history of drilling predation than previously assumed.