We describe the first record of a late Oligocene or early Miocene freshwater gastropod fauna from the Susuz  Formation of the Oltu-Narman Basin in northeastern Anatolia. The assemblage consists of only six species, indicating the presence of a well-oxygenated lake, pond or anabranch rich in vegetation. Only two of the taxa are related to European Oligo-Miocene species. The fauna might be the first indication of a yet undocumented Eastern Anatolian freshwater biogeographic region, characterized by high endemism and minor influence from the coeval Peri-Paratethyan and Aegean–Anatolian regions in the west. The biostratigraphic value of the assemblage is low but might rather point to a Miocene age of the upper part of the Susuz Formation. Theodoxus susuzianus, Bithynia erzurumensis, and Valvata koehleri are described as new species.

Key words: Mollusca, Gastropoda, Oligocene, Miocene, Turkey, Anatolia.

Mathias Harzhauser [mathias.harzhauser@nhm-wien.ac.at], Geological-Palaeontological Department, Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria. Thomas A. Neubauer [thomas.a.neubauer@allzool.bio.uni-giessen.de], Department of Animal Ecology & Systematics, Justus Liebig University, Heinrich-Buff-Ring 26-32 IFZ, 35392 Giessen, Germany, and Naturalis Biodiversity Center, PO Box 9517, 2300 RA Leiden, The Netherlands. İzzet Hoşgör [izzet.hosgor@calikenerji.com], Çalık Enerji, Oil and Gas Directorate, 06520, Söğütözü-Ankara, Turkey.