Population growth models of taxonomic radiations of clades from their origins have rarely been tested at the species level, on an evolutionary time scale. The diversification of Paleogene planktic Foraminifera following the mass extinctions at the Cretaceous-Tertiary boundary is tested for correspondence with the logistic growth model and paleoenvironmental record. An explosive initial diversification rate lasted less than 1 ma. A period of slow, fluctuating growth to a mid-Eocene maximum of 44 species followed. A large-diversity fluctuation at the Paleocene/Eocene boundary is caused by an extinction pulse and low origination rate. The rest of the Paleogene was marked by a very slow decline in species richness. There is no correlation between the record of temperature fluctuations and global diversity, except for the correspondence of the final phase of slow decline with a cooling of oceanic surface waters. Diversity data better fit a simple asymptotic rather than logistic or sigmoid curve. -from Author
