The evolutionary history of size variation of planktic foraminiferal assemblages in the Cenozoic

Here we document the accompanying size changes in entire planktic foraminiferal assemblages for the past 70 My and their relationship to paleoenvironmental changes. After the size decrease at the Cretaceous/Paleogene (K/P) boundary, high latitude assemblages remained consistently small.

Size evolution in low latitudes can be divided into three major phases: the first is characterized by dwarfs (65-42 Ma), the second shows moderate size fluctuations (42–14 Ma), and in the third phase, planktic foraminifers have grown to the unprecedented sizes observed today. Our analyses of size variability with paleoproxy records indicate that periods of size increase coincided with phases of global cooling (Eocene and Neogene).