Two alternative ages for the Montebamboli Oreopithecus (Late Miocene, Tuscany)

19th century scientists concerned with the interpretation of well and outcrop data collected during mining activities in southern Tuscany (Italy) agreed on the isochrony of the Montebamboli, Casteani, Ribolla and Montemassi Late Miocene black lignite and fetid limestone. The associated faunal and floral remains from the four localities, including the primate Oreopithecus bambolii Gervais, 1872, first described from a fossil collected at Montebamboli, were similarly interpreted as coeval. A second wave of scientists reconsidered the Montebamboli fossils during the 1950s, expanded the research to the Baccinello area, further south, and interpreted the Late Miocene record of Tuscany to signal instances of phyletic transitions among insular species. On the basis of palaeontological data, without discussing the correlations emerged during mining activities, the Montebamboli fauna was interpreted as a fauna younger than the fauna associated with the Casteani and Baccinello black lignite. The new point of view justified a palaeobiogeographic scenario characterised by multiple immigrations from the continental mainland to an insular Tuscan bioprovince, and from there to Sardinia, where an analogous Late Miocene Oreopithecus-associated insular fauna has been meanwhile studied. Based on old and new field data, the isochronic interpretation of the Montebamboli and Casteani black lignite is here resumed and an alternative palaeobiogeographic scenario is proposed, in the attempt to minimise inconsistencies that stem from the more recent school of thought. The alternative scenario points to a single phase of Tusco-Sardinian insularism bracketed between two intervals of faunal interchange when Tuscany and Sardinia came in contact with the continental mainland. Insularism took place within a single large island, or a single larger archipelago comprising southern Tuscany, Corsica and Sardinia, existing before and shortly after the opening of the Tyrrhenian Sea during the Tortonian.