METACRANGONYX-ILVANUS N. SP., THE FIRST ITALIAN REPRESENTATIVE OF THEFAMILY METACRANGONYCTIDAE (CRUSTACEA, AMPHIPODA)

Metacrangonyx ilvanus n.sp. is described from Elba Island; this is the first record of the family Metacrangonyctidae from Italy. The new spe cies belongs to the M. panousei-group, and more exactly to the M. gine ti-subgroup, previously known only from Morocco. This fact supports th e idea of a multiple colonization process of continental groundwaters from the sea. It is hypothesized that the ancestor of M. ilvanus n., s p. colonized brackish waters along the coasts of the Tethys sea and su rvived the oligomiocenic fragmentation of Thyrrhenis. A persistence of the species on a fragment of Thyrrhenis in the Tuscan archipelago or a more recent colonization of the older part of Elba Island from the S ardo-Corsican plate during the Messinian salinity crisis is suggested. More distributional data are needed to delineate the evolutionary sce nario of the genus in the Mediterranean area.