Investigation of pre-extinction dwarfing in Cenozoic planktonic foraminifera

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.