Evolutionary consequences of the latest Paleocene thermal maximum for tropical planktonic foraminifera

Study of planktonic foraminiferal assemblages preserved in the central, equatorial Pacific (ODP Site 865) reveal that genera which inhabited the near-surface, mixed layer diversified during the latest Paleocene thermal maximum (LPTM). This transient diversification gave rise to a suite of short-lived (50 to several 100 ka), distinctive morphotypes ( Morozovella allisonensis sp. nov., M. africana, and Acarinina sibaiyaensis) that are restricted to the LPTM interval. Parallel morphometric and stable isotopic data have been recorded from individual shells of members of the M. velascoensis/ M. allisonensis and A. soldadoensis/ A. sibaiyaensis lineages. The single-specimen isotope data confirm that M. allisonensis and A. sibaiyaensis are indeed stratigraphically restricted to the LPTM carbon isotope excursion; all specimens recorded anomalously low δ 13C values. A stratigraphic succession of single-specimen isotope data from within the δ 13C excursion interval was used to reconstruct the complex population dynamics which mediated the rapid (