Original paper

Der Gattung Nystia zugeordnete Arten im Tertiär des mittleren und westlichen Europas (Gastropoda: Rissooidea)

Kadolsky, Dietrich

Abstract

The taxonomy of Tertiary species of nonmarine Rissooidea currently placed in the genus Nystia was reviewed and as a result many species received new generic and even family assignments. The species remaining in Nystia s. str. are confined to the Latdorfian and Rupelian (Early and Middle Oligocene) of Western Europe;a preliminary revision of most taxa is given, and a tentative morphological evolution is proposed. The genus Nystia is removed from Hydrobiidae (Emmericiinae) and placed in Truncatellidae, together with Sandbergerina n. gen. and Staadtiellopsis. Eucbilus is removed from synonymy with Nystia and tentatively placed in Bithyniidae. The genera Schuettemmericia, Zilchiola n. gen. and Kuiperia are left in Hydrobiidae (Emmericiinae), the last two however tentatively. The type species of Schuettemmericia, hitherto poorly known, is shown to be a junior subjective synonym of "Nystia" lemani, whose distribution is extended from Aquitaine to SW. Germany. Other species now assigned to Schuettemmericia include 5. lenoiri, the type species of Staadtiella. The nomenclature of Stalioa is reviewed and its family attribution within the Rissooidea found to be uncertain. Zilcheuchilus, proposed as a subgenus of Stalioa, is closely related to Emmericia. The stratigraphy and palaeoecology of the species treated here is given, and the migration history of the taxa in the Rhenish-Hassian graben system is outlined.