The status of Arion alpinus Pollonera 1887, and re-description of Arion obesoductus Reischütz 1973 (Gastropoda, Arionidae)

In recent years two interpretations of Anion alpinus Pollonera 1887 have been proposed: a valid species with a central European distribution or a junior synonym of Arion intermedius Normand 1852. Study of the original description and topotypes collected in the only precise Piedmontese locality mentioned by Pollonera (1887), Rivarossa Canavese, demonstrate that the second is correct. To prevent Pollonera's species from continuing to be misinterpreted, a neotype of A. alpinus is designated from among these topotypes. The neotype clearly belongs to A. intermedius so the names are synonyms. Arion obesoductus Reischutz 1973, sometimes considered a synonym of A. alpinus, was described from juvenile specimens from Austria. Although a new study of adult topotypical specimens is desirable, anatomical re-examination of a paratype revealed characters typical of A. alpinus auctt. non Pollonera 1887, namely a long oviduct and a flat epiphallus papilla. These characters are also evident in adult specimens from Italy. The name A. obsesoductus is thus reinstated for Arion alpinus auctt. non Pollonera 1887, a species of several countries in Central Europe.