The Early Miocene (Burdigalian) mollusc fauna of the North Bohemian Lake (Most Basin) MATHIAS HARZHAUSER, THOMAS A. NEUBAUER, ELISAVET GEORGOPOULOU & JOSEF HARL We present a critical evaluation of the Early Miocene terrestrial and aquatic mollusc fauna of the North Bohemian Lake in the Most Basin in the Czech Republic. In total, 90 species (8 aquatic and 81 terrestrial gastropods, one bivalve) are documented from that lake system that had formed within the North Bohemian Rift. Only three of these species are newly recorded for the Most Basin, suggesting that the fauna is well sampled. Based on historical collections of the Nat- ural History Museum in Vienna, which were partly acquired by quantitative bulk samples from Tuchořice, a rough esti- mate of the composition of the terrestrial assemblage can be presented. More than 80% of the >30,400 shells are repre- sented by carychiids, vertiginids and valloniids, suggesting the presence of densely forested wetlands fringing the North Bohemian Lake. About 57% of the terrestrial species are known so far exclusively from the Most Basin. This high de- gree of “endemism”, however, is rather a result of the still very fragmentary knowledge of coeval European faunas. Dis- cus rasseri Harzhauser, Neubauer & Georgopoulou sp. nov. and Discus zagorseki Harzhauser, Neubauer & Georgopoulou sp. nov. are described as new species and Esuinella Harzhauser, Neubauer & Georgopoulou gen. nov. (Valloniidae), Nordsieckula Harl & Harzhauser gen. nov. (Orculidae), and Manganellia Harzhauser, Neubauer & Georgopoulou gen. nov. (Discidae) are introduced as new genera. Serrulastra (Serruplica) tuchoricensis nom. nov. is proposed as replacement name for Clausilia laevigata Frankenberger, 1914. • Key words: Gastropoda, Bivalvia, Mio- cene, Burdigalian, terrestrial ecosystems, Most Basin. HARZHAUSER, M., NEUBAUER, T.A., GEORGOPOULOU, E. & HARL, J. 2014. The Early Miocene (Burdigalian) mollusc fauna of the North Bohemian Lake (Most Basin). Bulletin of Geosciences 89(4), 819–908 (18 figures, 1 table). Czech Geological Survey, Prague. ISSN 1214-1119. Manuscript received February 10, 2014; accepted in revised form May 5, 2014; published online September 19, 2014; issued September 30, 2014. Mathias Harzhauser (corresponding author), Thomas A. Neubauer, Elisavet Georgopoulou & Josef Harl, Geologi- cal-Palaeontological Department, Natural History Museum Vienna, Burgring 7, A-1010 Vienna, Austria; mathias.harzhauser@nhm-wien.ac.at; thomas.neubauer@nhm-wien.ac.at; elisavet.georgopoulou@nhm-wien.ac.at; josef.harl@nhm-wien.ac.at The terrestrial and lacustrine mollusc assemblages from the Most Basin in Bohemia comprise one of the most di- verse Early Miocene (Burdigalian) non-marine mollusc faunas of Europe. Many extinct genera are based on spe- cies from Tuchořice and numerous authors referred to spe- cies from this locality when describing other European Cainozoic mollusc faunas. The exceptionally well-preserved fauna was initially described by Reuss in Reuss & Meyer (1849a, b). During the next decades additions and revisions were presented by Reuss (1861, 1868), Slavík (1869a, b), Boettger (1870a, 1877), Sandberger (1875), and Klika (1890). A first comprehensive synopsis of this pioneer phase was given by Klika (1891, 1892), followed by additional contribu- tions by Babor (1897), Flach (1889, 1891), Frankenberger (1912, 1914), Wenz (1915a), Thuma (1916, 1922) and Petr- bok (1925). The wealth of data and references were summa- rised again by Wenz (1923–1930). Since then no comprehen- sive evaluation of the fauna was performed. Instead, many authors discussed certain taxa – often with focus on other re- gional faunas or addressing specific taxonomic problems – introducing numerous new combinations (e.g. Pfeffer 1930; Wenz & Zilch 1959–1960; Schlickum 1968, 1970a, b; Schlickum & Truc 1972; Nordsieck 1972, 1981a, b, 1986; Schlickum & Strauch 1975; Strauch 1977; Moayedpour 1977; Falkner 1974, 1986; Richardson 1980; Prisyazhnyuk 1984; Čejchan 1985; Boeters et al. 1989; Kadolsky 1993; Stworze- wicz 1999a, b; Esu 1999; Manganelli & Giusti 2000a; Kadol- sky & Piechocki 2000; Kókay 2006; Schnabel 2006; Binder 2008). This kind of information is often hidden in the publica- tions as the relation to the Most Basin faunas is not always ob- vious from the titles. Moreover, only a very small percentage of the species has been depicted so far by photographs and SEM-micrographs. We present a synopsis of the Early Mio- cene molluscs from the North Bohemian Rift. We aim for an updated documentation and illustration of the fauna but do not consider this paper a critical revision of all taxa. 819 DOI 10.3140/bull.geosci.1503