Mare versus Lago-mare. Marine fishes and the Mediterranean environment at the end of the Messinian Salinity Crisis

During the late Messinian, c. 5.5 Ma ago, after evaporitic sedimentation and before the Pliocene flooding, the Mediterranean recorded a major environmental change testified by deposition of non-marine sediments of the so-called 'Lago-mare' facies. Such deposits are widespread in the Mediterranean basin, usually characterized by molluscs and ostracodes of brackish affinity. Here we present marine fish remains from 'Lago-mare' deposits of central Italy. The fossils, represented by both articulated skeletons and otoliths, were collected from nine stratigraphic horizons of the upper portion of the 'Lago-mare' sequence of Cava Serredi, Tuscany. Marine euryhaline fishes strongly dominate the assemblages but fully marine stenohaline fishes belonging to the families Myctophidae and Bythitidae are also present. The fossil fish remains are associated with classic 'Lago-mare' ostracodes and molluscs. These fossil fishes clearly demonstrate that normal marine conditions were present at least during the upper interval of the 'Lago-mare' event, implying that the marine refilling of the Mediterranean was intra-Messinian rather early Pliocene. We argue in favour of the necessity of a new palaeoenvironmental interpretation for the post-evaporitic Messinian of the Mediterranean.