(Table 1) Test sizes of Morozovelloides crassatus from ODP Site 171-1052

We propose a phenomenon termed “pre-extinction dwarfing” in Cenozoic planktonic foraminifera. High-resolution morphometric analysis shows a reduction in maximum or mean test size in the 2-20 kyr interval preceding the extinction of Pliocene Globorotalia exilis and Globorotalia miocenica from the Caribbean Sea and middle Eocene Morozovelloides crassatus from the western North Atlantic. Through a series of case studies and review of qualitative observations from the literature, we suggest that dwarfing occurs in a number of species of planktonic foraminifera foreshadowing their demise and that such size changes are not just a phenomenon associated with mass extinction events. We propose that this is a common stress-induced pattern that results in diminutive size in the pre-extinction interval.

我们提出了新生代浮游有孔虫（planktonic foraminifera）中一种被命名为“灭绝前矮化（pre-extinction dwarfing）”的现象。高分辨率形态计量分析结果表明，在加勒比海上新世纤细抱球虫（Globorotalia exilis）、中新抱球虫（Globorotalia miocenica），以及西北大西洋中部中始新世厚拟球旋虫（Morozovelloides crassatus）的灭绝事件前2至20千年（kyr）的时间间隔内，这些物种的最大或平均壳体尺寸均出现了缩减。通过一系列案例研究以及对文献中定性观测结果的综述，我们认为，多种浮游有孔虫在灭绝前均会出现矮化现象，这预示着它们即将走向消亡；且此类体型变化并非仅与集群灭绝事件相关。我们提出，这是一种普遍存在的由胁迫诱导的演化模式，会使物种在灭绝前的阶段呈现小型化特征。