Upper Miocene molluscs of the Ponsano Sandstone (northern Apennines, Italy): revision of the collection at the Museo di Storia Naturale, Università di Pisa

The revision of fossil specimens mainly collected in the sixties of the last century and today hosted at the Museo di Storia Naturale of Pisa allowed to update the taxonomy of Lower Tortonian bivalves and some gastropods of the Ponsano Sandstone, cropping out in southern Tuscany in the Pisa and Siena provinces. The stratigraphy of the original successions was reconstructed and quantitative data were estimated by counting museum specimens and by transforming literature semiquantitative data into quantitative ones. The paleoecology of three successive main assemblages has been defined by measuring the relative abundance of bivalves and the transgressive-regressive trend of the succession in the type area (previously known from sedimentary and micropaleontological data) has been confirmed for the first time based on the macrofauna.