Taphonomy, palaeoecology and palaeobiological significance of the Cisterna quarry fossil site: An exceptional window into the marine vertebrate biodiversity of the early Late Miocene Mediterranean Sea

During the Late Miocene, the marine fauna of the Mediterranean Sea underwent remarkable modifications driven by global cooling and regional oceanographic changes that climaxed with the Messinian Salinity Crisis. Here, we provide a comprehensive synopsis of the outstanding marine vertebrate assemblage from the Tortonian strata of the Pietra leccese limestone exposed at the Cisterna quarry, some 2 km southeast of Lecce (southern Italy). This thoroughly monitored locality has yielded an impressive vertebrate fauna, including cetaceans (both odontocetes and mysticetes, among which are the holotypes of the macroraptorial sperm whale Zygophyseter varolai, the stem beaked whale Messapicetus longirostris and the archaic grey whale Archaeschrichtius ruggieroi), sea cows (Metaxytherium medium), hard-shelled sea turtles, bony fishes (including the holotypes of Makaira adensa, Makaira cyclovata, Pizzikoskerma salentina and Sicophasma macrocanalata among other istiophorid billfishes) and elasmobranchs. Taphonomic evidence, including bone modifications consistent with the activity of offshore bioeroders such as Osedax, provides new insights into the preservation and palaeoenvironmental context of these remains. The Cisterna fauna records a warm-water, nutrient-rich, offshore setting and illuminates a key phase in the evolutionary history of toothed whales. Its longirostrine ziphiids and macroraptorial sperm whales reflect predator ecomorphs that were soon to decline globally, while the close affinities between M. longirostris and the Peruvian Messapicetus gregarius point to interchanges between the southeastern Pacific and Atlanto-Mediterranean marine vertebrate faunas through the then-open Central American Seaway. Taken together, the Cisterna quarry preserves a uniquely well-resolved marine vertebrate assemblage that serves as an unparalleled testament to the Late Miocene marine biodiversity of the Mediterranean Sea.