T102 Topics in Paleoecology: Predation/Biotic Interactions, Fidelity/Taphonomy, and Community Ecology/Whole Organism Paleoecology (Posters)

Monday, 5 November 2012
9:00 AM - 6:00 PM
Hall B

INTENSE NATICID DRILLING PREDATION ON TURRITELLINE GASTROPODS FROM THE LATEST CRETACEOUS INDIA

Paper number: T102-7
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Previous studies suggest that naticid predation intensity, measured as the drilling frequency, was relatively low in the Cretaceous than the Cenozoic values. In the present study, we tested this hypothesis with a new dataset of naticid predator and their turritelline prey from a “Turritelline-dominated assemblage” or TDA from the latest Cretaceous sections in Rajahmundry, India. Our dataset includes 2 species of turritelline gastropods (Turritella dispassa and T. neptuni ) and 2 species of naticid gastropods (Mammila carnatica and M. sp.), collected from 8 bulk samples, consisting of 13,491 specimens. Our results show that drilling intensity was 24.09% (for T.dispassa). Even when we incorporated the drilling data of the other species T. neptuni the drilling frequency of turritelline gastropods thus becomes 22.95%, which is still significantly higher than previously reported values. The analysis also suggests that this high frequency is not a result of higher abundance of turritelline prey in our samples. The Indian fossil record also shows that many naticid behaviors, for example size and site stereotypy which are the characteristic features of Cenozoic predators, have also been established in the present Cretaceous assemblage.

This study extends the palaeobiogeography of naticid predation from western world to India, which was located in the southern hemisphere during the Cretaceous. One factor that can account for some of the differences between previous studies and our results is the sample size. Previous studies suggested that reported low value of drilling frequency during the Cretaceous may be an artifact of small sample size. Our study reports the biggest sample size for a lineage-level study,. Secondly, we also maintain that this high drilling intensity in our sample may be a manifestation of higher predation intensity in local biogeographical pockets. However, spatial heterogeneity of naticid predation is not a feature of the Cretaceous only; it is also documented in present day. We, therefore, conclude that any impact of Mesozoic Marine Revolution on turritelline prey must have happened before the late Cretaceous and the idea that drilling frequency became low immediately below the K –T boundary mass extinction is not a general trend.