The extinct catshark Pachyscyllium distans (Probst, 1879) (Elasmobranchii: Carcharhiniformes) in the Pliocene of the Mediterranean Sea

Abstract

Sharks assigned to the carcharhiniform family Scyliorhinidae account for about 160 extant species placed in 18 genera. Most living scyliorhinids are small- to medium- sized ground sharks provided with cat- like eyes and nasal barbels similar to whiskers; hence their vernacular name, "cat- sharks". Living catsharks mostly inhabit deep or rather deep waters of the warm and temperate seas worldwide, foraging on small fishes and inverterbates. In the present paper, we report on a lateral tooth of Scyliorhinidae collected from a clay pit at Certaldo (central Italy), where marine mudstones belonging to the famously fossiliferous Pliocene successions of Tuscany are exposed. This catshark specimen represents the second bona fide record of the extinct premontreine species Pachyscyllium distans in the Pliocene of the Mediterranean Sea, as well as the geologically youngest confirmed occurrence of this species worldwide. In the Mediterranean Pliocene, P. distans thus coexisted with the similar but distinct species Pachyscyllium dachiardii. After having been widespread in Northern Atlantic, Paratethyan, and Mediterranean waters in Miocene times, P. distans became confined to the Mediterranean Sea during the Pliocene. Therefore, similar to what has recently been suggested for P. dachiardii, we hypothesise that the range of P. distans contracted southward as colder conditions took hold in the Northern Hemisphere. The eventual extinction of P. distans might be related to the first cooling episode that significantly affected the Mediterranean biota around 3 Ma.