Revealing the stygobiotic and crenobiotic molluscan biodiversity hotspot in Caucasus: Part I. The phylogeny of stygobiotic Sadlerianinae Szarowska, 2006 (Mollusca, Gastropoda, Hydrobiidae) from Georgia with descriptions of five new genera and twenty-one new species Author Grego, Jozef Horna Micina 219, 97401, Banska Bystrica, Slovakia Author Mumladze, Levan Institute of Zoology, Ilia State University, Kakutsa Cholokashvili Ave 3 / 5, Tbilisi 0162, Georgia https://orcid.org/0000-0002-2172-6973 Author Falniowski, Andrzej Department of Malacology, Institute of Zoology and Biomedical Research, Jagiellonian University, ul. Gronostajowa 9, 30 - 387, Krakow, Poland Author Osikowski, Artur Department of Animal Reproduction, Anatomy and Genomics, University of Agriculture in Krakow, al. Mickiewicza 24 / 28, 30 - 059, Krakow, Poland https://orcid.org/0000-0001-6646-2687 a.osikowski@urk.edu.pl Author Rysiewska, Aleksandra Department of Malacology, Institute of Zoology and Biomedical Research, Jagiellonian University, ul. Gronostajowa 9, 30 - 387, Krakow, Poland Author Palatov, Dimitry M. Department of Hydrobiology, Biological Faculty, Moscow State University, 1 - 12 Leninskie Gory, 119991, Moscow, Russian Federation Author Hofman, Sebastian Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Jagiellonian University, ul. Gronostajowa 9, 30 - 387, Krakow, Poland text ZooKeys 2020 955 1 77 http://dx.doi.org/10.3897/zookeys.955.51983 journal article http://dx.doi.org/10.3897/zookeys.955.51983 1313-2970-955-1 C8EF4A4B6F054621B9B5AE47FEE7C217 F7018CF19C6158309D57C83A2F5E9478 Genus Hausdorfenia Grego & Mumladze gen. nov. Type species. Hausdorfenia pseudohauffenia Grego & Mumladze, sp. nov. Species assigned to the genus. Hausdorfenia shareula Grego & Mumladze, sp. nov. Diagnosis. The new genus differs from Pontohoratia Vinarski, Palatov & Gloeer , 2014 by its flatter shell shape, more coarsely pitted protoconch and by its operculum with a distinct peg on its inner side. The molecular data support the closest relationship is to the genus Kartvelobia gen. nov.; however, its valviform shell shape is substantially different from the elongate oval shape and aperture morphology of its relative. Etymology. Name derived from Bernhard Hausdorf, Hamburg University (Germany), who contributed much to the study of Mollusca from whole Caucasus region. Distribution. Known from the karstic plateau of Shaori (შაორის კარსტული პლატო ) and adjacent stygobiotic habitats (Fig. 15 ).