Ichnusomunda sacchii a new hygromiid snail from Sardinia Island (Western Mediterranean): an intriguing case of homoplasy in the anatomical organization (Pulmonata: Hygromiidae)

Ichnusomunda sacchii, new genus and new species, is described from Sardinia. The new genus is anatomically characterized by: right ommatophore retractor independent of genitalia; penial nerve from right pedal ganglion; left lateral lobe of pallial margin long; vagina with digitiform glands and 0 + 2 dart-sac complex, the latter consisting of elongated, wide, cylindrical basal portion, joined perpendicular to distal vagina, at the apex of which two stylophores open side-by-side; outer stylophore small, globular, with thick, muscular walls, secreting dart; inner stylophore long and slender, with thin walls and wide, empty (dartless) lumen, bent to adhere to upper side of basal portion; penis with long, cylindrical penial papilla having three basal frenula. This combination of anatomical characters is unique and distinct from those in the other genera of the Hygromiidae. Some of these characters (pedal penial innervation; three frenula at the base of penial papilla) are shared with Cernuella (Cernuella) and Cernuella (Xeroamanda), others (basal portion of dart-sac complex; structure of inner stylophore) with Xeromunda, Xerolenta, and Pseudoxerophila. I. sacchii has a limited distribution, being known only from the type locality, the sand dunes of Riu Piscinas, a very important biotope of western Sardinia (no. 20/35 in the checklist of the Societa Botanica Italiana; no. ITB000031 of the "Nature-2000 Web"). Although I. sacchii is very common in this site, its limited distribution is a clear risk factor in the face of man-made modifications to the peculiar habitat in which it lives.