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

The iterative evolutionary radiation of planktic foraminifers is a well-documented macroevolutionary process. 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. […]

浮游有孔虫的迭代进化辐射是一个记载详尽的宏观进化过程。本研究详细记录了过去7000万年期间整个浮游有孔虫群的尺寸变化，以及这些变化与古环境变化的关联。在白垩纪-第三纪（K/P）界线处的尺寸减小之后，高纬度地区的有孔虫群始终保持较小的体型。低纬度地区的尺寸演化可分为三个主要阶段：第一阶段以侏儒型（65-42百万年前）为特征，第二阶段表现为中等尺寸的波动（42-14百万年前），而在第三阶段，浮游有孔虫的体型增长至如今所观察到的前所未有的大小。