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 Pontohoratia mapeli Grego & Mumladze sp. nov. Fig. 16E, F ; Plates 20 (6); 21(4); 22(1-4) Type locality. Georgia • Samegrelo, Kanti Village near Mukhuri, Mapeli Spring (მაპელის წყარო , სოფელი კანტი ); 42°38'23"N , 42°10'08"E ; 290 m a.s.l. Material. Holotype : Georgia • 1 adult, dry; type locality; 06 May 2018; J. Grego, L. Mumladze and M. Olsavsky leg.; ISU FM-T021-H. Paratypes : Georgia • same as for holotype; col. JG F1060/5 dry; • same as preceding; 12 October 2019; J. Grego, L. Mumladze and G. Bananashvili leg.; ISU FM-T021-P1/ 40 dry and 69 wet, SBMNH 635896/6 dry, NHMW 113375/2 dry, HNHM 104684/2 dry, NHMUK 20191340/2 dry, NHMB 563972/2 dry, SMF 358931/2 dry, ZMH 140636/2 dry, MNHN-IM-2016-7900, ZIN 1/503-2020/2 dry, coll. JG F1413/40 dry and 69 wet, coll Gloeer /1 dry. Diagnosis. The shell of the new species is more flat-discoid with a more open umbilicus, more rounded and proportionally smaller aperture vs. the geographically closest relatives: P. vinarskii sp. nov. and P. pichkhaiai sp. nov. The shell shape is somewhat similar to H. pseudohauffenia , but it can be differentiated by less pronounced protoconch, lower shell height to width ratio the proportionally smaller, more rounded aperture as well by its operculum lacking the knobby sculpture. Description. Shell : small, paucispiral, discoid with flat, only slightly pronounced spire and widely opened umbilicus. Diameter 1.37-1.51 mm. The inflated whorls are separated by a deeply cut sulcus. Protoconch surface covered by dense shallow pits. The shell surface whitish and translucent with smooth surface. The aperture round with labral peristome oblique to the columellar axis. The aperture barely attached at its upper columellar side to the body whorl. Protoconch surface covered by raised malleations gradually changing to a regular pitting towards the nucleus. Operculum : reddish, circular, paucispiral with central nucleus, centrally thickened and elevated inward without peg. Holotype measurements : H-0.57 mm; W-1.38 mm; BH-0.55 mm; BW-0.95 mm; AH-0.42 mm; AW-0.45 mm; CA: -40°. Anatomy : the penis (Fig. 16E, F ) proximally broad, with a broad, slightly marked outgrowth on its left side in the median part, and thin filament distally. Etymology. Name derived from the name of Mapeli (მაპელი) Spring in Kanti (კანტი) Village, the type locality of the species. Habitat. Stygobiotic species. See the habitat of Caucasogeyeria chrysomallos sp. nov. Distribution. Only known from the type locality. Conservation status. The number of known locations (1) is no more than 5 and EOO is smaller than 20 km2. There is no reason to suppose that AOO, EOO, number of locations, number of subpopulations or the number or mature individuals are declining however due to its extremely small EOO we assessed as Vulnerable (VU) D2.