A Monachinae tooth from the Tortonian of Cessaniti (Calabria, Italy) and some remarks on the fossil record of pinnipeds in the Mediterranean basin

The fossil record of Pinnipedia (seals, sea lions and walruses), the second most diverse extant clade of marine mammals after cetaceans, dates back to the late Oligocene-earliest Miocene. Herein, we describe an isolated left premolar of Monachinae indet. (Phocidae) from the Tortonian (Upper Miocene) of Cessaniti, Calabria, Italy. This specimen was collected in unit SH3, where several skeletons of the sirenian Metaxytherium serresii were also found, along with bone remains of an indeterminate physeteroid cetacean, the giraffid Bohlinia, and the proboscidean Stegotetrabelodon. We discuss the fossil record of pinnipeds in the Mediterranean basin, noting that the Cessaniti monachine tooth represents the second undisputed Miocene pinniped record from Italy following the discovery of the Noriphoca gaudini skull more than 150 years ago. Additionally, we observe that all fossil pinnipeds found in the Mediterranean, including the one from Cessaniti, belong to the Monachinae or related basal Phocidae. This fact supports the hypothesis that the Mediterranean was a significant area for the diversification of this pinniped lineage. However, due to the fragmentary nature of the Mediterranean pinniped fossil record, it remains unclear whether the Mediterranean pinnipeds evolved separately over time within this basin or if there were one or more colonization events from the Atlantic, possibly including one following the Messinian Salinity Crisis.