SIZE, DIVERSITY, AND ECOLOGY OF TURRITELLINE GASTROPODS ACROSS A COMPLEX MASS EXTINCTION BOUNDARY (PLIO-PLEISTOCENE, U.S. ATLANTIC COAST)

The Plio-Pleistocene mass extinction in the western Atlantic is poorly understood, but many researchers have argued that the event occurred in two pulses, with at least one phase characterized by a drop in marine primary productivity. Response of suspension-feeding taxa might therefore be of particular interest for investigating the dynamics of this event. We have expanded on previous preliminary work on turritelline gastropods, which are mainly suspension-feeders, from the Pliocene and Pleistocene of Florida and the Atlantic Coastal Plain, using stable isotope sclerochronology to determine longevity and growth rates of several turritelline species spanning the two phases of the extinction event. Cumulative results reveal that, prior to the extinction, Pliocene turritellines showed a wide range of size and growth rate (from small and long-lived to large and short-lived). After the first phase of extinction, the largest species became extinct, regardless of longevity (i.e., variation in longevity is reduced but still present). The second phase saw the disappearance of all types except for very small and short lived species. Our results show a selectivity for progressively smaller species, but with notable reduction in longevity occurring only after the second phase of extinction. The significance of these results for hypotheses of environmental cause of the extinction remains unclear.