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 Imeretiopsis cameroni Grego & Mumladze sp. nov. Plates 8 (7, 8); 9(8) Type locality. Georgia • Imereti, Kutaisi, Iazoni (Tskhal-Tsiteli) Cave spring (იაზონის იგივე წყალ-წითელას მღვიმე ), right bank of Tskalsitela River; 146 m alt., 42°16'18"N , 42°44'2"E ; 145 m a.s.l.; sandy sediment inside the cave. Material. Holotype : Georgia • 1 adult, dry; type locality; 01 May 2018; J. Grego, L. Mumladze and M. Olsavsky leg.; ISU FM-T016-H. Paratypes : Georgia • same as for holotype; 12 October 2019; J. Grego, L. Mumladze and G. Bananashvili leg.; 4 ISU FM-T016-P1/1 dry, JG F1406/1 dry, ZIN 1dry. Diagnosis. The new species differs conspicuously from all the similar species of the region by its more slender shell with more conspicuous axial growth lines, closed umbilicus and narrower aperture. Caucasogeyeria orientalis (Starobogatov, 1962) has a similar, but more robust, oval shell shape with a different shape of the aperture. Description. Shell : elongate narrow-turreted, 2.00-2.29 mm high shell with 51/2 tumid whorls, weak suture and flat blunt apex. The early whorls rather inflated, and the inflation of whorls regularly decreasing abapically, apex almost flat. Shell surface glossy, whitish translucent with faint regularly spaced distant rib-like growth lines. Umbilicus closed. Aperture not expanded, elongate-oval with weakly sinuated labral profile and flat columellar profile. Protoconch pitted. Operculum : light yellow, horny, elongate ellipsoid, paucispiral with excentric nucleus. Animal body : not known. Holotype measurements : H-2.00 mm; W-0.81 mm; BH-0.96 mm; BW-0.72 mm; AH-0.62 mm; AW-0.49 mm; CA: 35° Anatomy : not known. Etymology. Named after Robert A. D. Cameron from Sheffield University, who significantly contributed to the malacological knowledge of Eurasia including Caucasus region. Habitat. Stygobiotic species. The fresh empty shells, some with opercula, were found in the sandy sediment of the cave stream. The condition of the shells indicates its habitat in the deep cave zone. Distribution. Only known from the type locality. Conservation status. The species is known from a single location and EOO is smaller than 10 km2. There is also indication of stochastic human driven habitat pollution and a very scare occurrence of dead mature individuals indicating a very weak surviving population. Therefore, it is assessed as Critically endangered (EN) B2. Remarks. The assignment of the new species to the genus Imeretiopsis gen. nov. is only provisional, based on the shell habitus, e.g., the similarly sinuated lateral labral profile. Molecular data will be necessary to confirm the taxonomic position of the species. The type locality, Iazoni Cave was formed in Cretaceous limestone with a high content of quartz sand grains. The sand accumulated in thick sedimentary layers after the carbonate dissolution inside the cave. A few kilograms of the cave sand had to be screened to find a single specimen. The cave drains water from a populated area SE of Kutaisi, and the sediments indicated a contamination by micro plastic and perhaps occasionally by chemicals from municipal waste. This can pose a direct danger to the important cave fauna including Motsametia borutzkii (Shadin, 1932), Euglesa subterranea (Shadin, 1932) and cave shrimps Xiphocaridinella kutaissiana Sadowski, 1930, Niphargus borutzkyi Birstein, 1933 and Asellus monticola fontinalis Birstein, 1936 reported from the type locality.