Did the smalleye hammerhead ever inhabit the Mediterranean Sea?

Abstract

Three species of Sphyrna (S. lewini, S. mokarran and S. zygaena) are known to inhabit the present-day Mediterranean Sea, whereas uncertainties exist about the presence of S. tudes in the same basin. Indeed, the presence of this typically westernAtlantic shark in the Mediterranean Sea is supported by as few as two historical specimens that were captured at Nice (southeastern France) and Leghorn (northern Tyrrhenian coast of central Italy). Here, we provide a redescription and an updated taxonomic identification of the Leghorn specimen of smalleye hammerhead, which is currently kept in the zoological collection of the Natural History Museum of the University of Pisa and is believed by some authors to represent a misidentified representative of S. lewini. Based on first-hand observations, we confirm the taxonomic identification of this specimen as belonging to S. tudes. Considering the ontogenetically young nature of both the Nice and the Leghorn specimens of S. tudes, parturition in the Mediterranean Sea is hypothesised, which in turn may evoke the occurrence of a population of smalleye hammerheads inhabiting this basin at least as recently as the early 19th century.