Drilling gastropod predation on the lower Miocene gastropod assemblages from Kutch, western India: spatiotemporal implications

Unambiguous gastropod drilling predation has been reported in shells of Cretaceous age onwards. Global data suggest that the drilling intensity shows wide spatial variation throughout the Miocene. In order to understand the factors controlling geographic variability in drilling predation, data from many regions are needed. The present study includes detailed analyses of drilling intensity (DI) of predation, its spatial variability, and behavioural stereotypy within the lower Miocene gastropod assemblages of the two formations of Kutch, India. The studied area was positioned at about 17⁰N latitude during the lower Miocene. DIs calculated from 25,766 gastropod specimens in the assemblage, as well as at lower taxon levels, are relatively low for the entire lower Miocene. Prey effectiveness (PE) and Multiple drill holes (MULT) are also low. DI in each formation shows spatial variability which is not related to the number of samples per location and specimen numbers. Temporally, DI increases from the Aquitanian to the Burdigalian, and this rise is statistically significant. Low abundance of the predators and bivalves as a potential prey item are two possible causal factors for the low DI’s observed.