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. (C) 2009 Elsevier B.V. All rights reserved.