Holoplanktonic mollusca: Development in the mediterranean basin during the last 30 million years and their future

Abstract

A short introduction is given to the systematics and morphology of pelagic Gastropoda (Mollusca: Heteropoda and Pteropoda), also explaining some details of the animals' particular way of life. The fossil record of these invertebrates is discussed briefly, followed by an overview of existing literature, focussing on the Mediterranean Basin. Developments during the Mediterranean Cenozoic are explained stage by stage and the numerical occurrences of species within the basin are correlated with palaeo-temperatures, generally with very good results. In the same context illustrations are added of index species or otherwise interesting taxa. The very intensively studied Quaternary occurrences are referred to briefly, citing other papers recently published. A preliminary Mediterranean biozonation scheme, recently developed and based on fossil Pteropoda, is referred to and schematically included in one of the illustrations. In the last part, we discuss possible future developments of holoplanktonic molluscs, resulting on the one hand from increased knowledge of the systematics, phylogeny and biogeography due to recent interest in this group and the application of modern powerful morphometric and molecular techniques. On the other hand, there exist major concerns about the future of this group resulting from the (combined) effects of global warming and ocean acidification.