The Early Miocene (Burdigalian) mollusc fauna of the North Bohemian Lake (Most Basin).

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 Natural History Museum in Vienna, which were partly acquired by quantitative bulk samples from Tuchořice, a rough estimate of the composition of the terrestrial assemblage can be presented. More than 80% of the >30,400 shells are represented 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 degree of "endemism", however, is rather a result of the still very fragmentary knowledge of coeval European faunas. Discus 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. [ABSTRACT FROM AUTHOR]