New hydrobiids from subterranean waters of eastern Sardinia, Italy (Gastropoda Prosobranchia: Hydrobiidae)

Although the discovery of stygobiont hydrobiids in the groundwaters of Sardinia (Italy) is very recent, many taxa have been identified supporting the fact that the Sardinian hydrobiid stygofauna is the richest and most diversified of all the Mediterranean islands. Two new genera and three new species discovered in the karstic systems of eastern Sardinia, north of the Gennargentu massif are described: Sardopaladilhia nov. gen., Sardopaladilhia plagigeyerica nov. spec., Sardohoratia nov. gen., Sardohoratia sulcata nov. spec., and Sardohoratia islamioides nov. spec. Like many other genera of hydrobiids, Sardopaladilhia and Sardohoratia have mosaics of characters, some of which are shared with other groups of hydrobiids. Based on the number of characters shared, the genus closest to Sardopaladilhia is Paladilhia Bourguignat, 1865, and that closest to Sardohoratia is Horatia Bourguignat, 1887. Sardopaladilhia differs from Paladilhia in a number of important characters, the most evident of which is the peculiar stylet at the apex of the penis. Sardohoratia differs from Horatia by virtue of the penis without lateral lobe. The two species of Sardohoratia are easily distinguished from each other. They have quite different shell shapes and some anatomical differences; their coexistence in the same karstic systems and the absence of intermediate specimens supports distinct specific status. The fossil Islamia sarda Esu, 1984, is tentatively assigned to Sardohoratia. The three new species occur in a few restricted areas of eastern Sardinia and the two species of Sardohoratia can be considered threatened.