Taxonomic diversity and stratigraphic distribution of Mediterranean Pliocene bivalves

The mollusc disappearance–extinction events throughout the Mediterranean Pliocene suggest the definition of four faunistic units [Mediterranean Pliocene Molluscan Units (MPMUs)]. The bivalve taxonomic diversity, the paleobiogeographic significance and the chronological classification of each unit are analyzed in detail. The boundaries of the MPMUs approximate the major climatic changes of the Northern Hemisphere, respectively at 3.0, 2.5 and 2.1 Ma. On the whole, the molluscan fauna changes (356 species of shallow water bivalves have been considered) record the transition from a tropical unit (MPMU1) to a biogeographic unit (MPMU4) comparable with that of the Recent Mediterranean.