NATICID DRILLING PREDATION ON GASTROPOD ASSEMBLAGE DURING THE LATEST MAASTRICHTIAN IN RAJAHMUNDRY, INDIA
Here, we tested this hypothesis with 31,929 gastropod specimens from the latest Maastrichtian Infratrappean bed in Rajahmundry, India. Our study suggests that assemblage-level naticid drilling frequency was significantly higher (~28%) than previously reported. Although relative abundance of different lineages varies within this assemblage, lineage-level drilling frequency also supports our finding of high drilling intensity in the Cretaceous. Naticid predators were highly efficient as it was evident from high DF (drilling frequency) and low PE (prey effectiveness) values as well as site and size stereotypy of the drillholes.
We conclude that naticid drilling-induced escalation was already established during the Cretaceous and the present find extends the paleobiogeography of naticid predation up to India. One potential explanation of higher drilling frequency in our Cretaceous samples is that while all other previous studies come from high latitude localities in U.S.A. and western Europe, Rajahmundry area belonged to the Northern sub-tropic during the Maastrichtian. Some of the previous studies indicated that naticid predation on modern taxa often shows a latitudinal gradient, i.e., increasing drilling frequency with decreasing latitude. Alternatively, our study may represent a local biogeographical hotspot of higher drilling intensity within a mosaic pattern of spatially heterogeneous naticid predation.