Alopias grandis (Leriche, 1942) from the Miocene of Italy: insights on a rare species of giant thresher shark

Teeth assigned to the extinct shark species Alopias grandis (Lamniformes: Alopiidae) are described herein from two Miocene deposits of southern Italy, namely, the Burdigalian to Messinian Pietra leccese limestone and the Serravallian to Tortonian “Aturia level” of the Salento Peninsula (Apulia). This is the first published record of this rare species of thresher shark in Italy. The newly documented teeth from the “Aturia level” may represent the geologically youngest finds of A. grandis worldwide. Alopias grandis and the allied species Alopias palatasi (another giant thresher provided with coarsely serrated teeth) represent a palaeontological conundrum, as very little is known about their body aspect and palaeobiology, but they have been interpreted as larger-bodied, higher-trophic level sharks compared to their extant congeners. Here, we contend that these giant Alopias species contribute significantly to making the dental disparity of the Miocene macrophagous mackerel sharks higher than that shown by the extant lamniform stock, which in turn evokes peculiar mechanisms of trophic partitioning that are no longer at play today.