Hypselostomatidae is a large family of terrestrial pulmonate molluscs currently represented by 284 extant species, most confined to Southeast Asia. The current system of grouping species into genera is based on the morphology of the apertural barriers and the level of last whorl detachment. However, these characters overlap, challenging generic definitions. In this paper, these characters are evaluated and a novel classification proposed for hypselostomatid species belonging to the genera Anauchen (17 species), Bensonella (36 species), Boysidia (7 species, in part) and Hypselostoma (85 species). We assigned all species belonging to the genera Bensonella and Hypselostoma into two and four species groups respectively, which are characterised by combinations of morphological traits. Altogether 46 new species are described, seven species in Anauchen: A. crassus Gojšina, Hunyadi & Páll-Gergely, sp. nov., A. evanidus Gojšina & Páll-Gergely, sp. nov., A. grandiportus Gojšina, Grego & Páll-Gergely, sp. nov., A. obesus Gojšina, Hunyadi & Páll-Gergely, sp. nov., A. picasso Gojšina & Páll-Gergely, sp. nov., A. turritus Gojšina, Hunyadi & Páll-Gergely, sp. nov., A. jokaii Gojšina & Páll-Gergely, sp. nov.; 19 species in Bensonella: B. alycaeus Gojšina & Páll-Gergely, sp. nov., B. cardiostoma Gojšina, Vermeulen & Páll-Gergely, sp. nov., B. cristatissima Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. dha Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. dracula Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. exploda Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. fracta Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. microdentata Gojšina & Páll-Gergely, sp. nov., B. mitochondria Gojšina, Vermeulen & Páll-Gergely, sp. nov., B. mirabilis Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. montawa Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. multidentata Gojšina, A. Reischütz & Páll-Gergely, sp. nov., B. nitens Gojšina & Páll-Gergely, sp. nov., B. obex Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. perfecta Gojšina & Páll-Gergely, sp. nov., B. sericata Gojšina & Páll-Gergely, sp. nov., B. serrata Gojšina, Hunyadi & Páll-Gergely, sp. nov., B. spelaea Gojšina, Grego & Páll-Gergely, sp. nov., B. spinosa Gojšina, Hunyadi & Páll-Gergely, sp. nov.; 20 species in Hypselostoma: H. aquila Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. bubalus Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. circumcarinatum Gojšina, Auffenberg & Páll-Gergely, sp. nov., H. coriaceum Gojšina & Páll-Gergely, sp. nov., H. aenigma Gojšina, Grego & Páll-Gergely, sp. nov., H. fortunatum Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. fungus Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. geckophilum Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. iunior Gojšina & Páll-Gergely, sp. nov., H. ophis Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. platybasis Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. populare Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. sculpturatum Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. similare Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. sorormajor Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. sororminor Gojšina, Hunyadi & Páll-Gergely, sp. nov., H. torta Gojšina, Auffenberg & Páll-Gergely, sp. nov., H. vesovici Gojšina & Páll-Gergely, sp. nov., H. vicinum Gojšina, Auffenberg & Páll-Gergely, sp. nov., H. vujici Gojšina & Páll-Gergely, sp. nov. One replacement name is proposed: H. tertiusfrater Gojšina & Páll-Gergely, nom. nov. pro Boysidia salpinx F. G. Thompson & Dance, 1983, non Hypselostoma salpinx (van Benthem Jutting, 1961) (originally described as Gyliotrachela). Gyliotrachela and Antroapiculus are both treated as junior synonyms of Hypselostoma. An additional 28 species and subspecies are reassigned to the synonymies of other taxa.

During a field trip to the western part of the Balkan Peninsula in 2016, investigations of several caves and karstic springs revealed six new gastropod species living in subterranean waters and resulted in some noteworthy faunistic records. Five of the new species are assigned to the genus Paladilhiopsis Pavlović, 1913, namely P. prekalensis sp. n., P. lozeki sp. n., P. szekeresi sp. n., P. wohlberedti sp. n., P. falniowskii sp. n. and one to the genus Plagigeyeria Tomlin, 1930, namely P. steffeki sp. n. New Albania and Kosovo distribution records are given for Iglica illyrica Schütt, 1975, Plagigeyeria zetaprotogona Schütt, 1960, Vinodolia matjasici (Bole, 1961), and the first georeferenced record is given for Saxurinator schlickumi Schütt, 1960. The most important environmental factors influencing habitat selection of these subterranean freshwater gastropods are briefly discussed.

Nineteen new species of the alycaeid genera Chamalycaeus, Dicharax, and Metalycaeus are described from Thailand and Myanmar: Chamalycaeus buaboke Páll-Gergely & A. Reischütz, n. sp., C. erawan Páll-Gergely & Hunyadi, n. sp., C. hirpex Páll-Gergely & A. Reischütz, n. sp., C. irmatallus Páll-Gergely, n. sp., C. krabiensis Páll-Gergely & A. Reischütz, n. sp., C. serratus Páll-Gergely & Auffenberg, n. sp., C. spiratus Páll-Gergely, n. sp., Dicharax (?) admirandus Páll-Gergely & Auffenberg, n. sp., D. cyclostoma Páll-Gergely, n. sp., D. ebrius Páll-Gergely & Auffenberg, n. sp., D. (?) gnomus Páll-Gergely, n. sp., D. mirounga Páll-Gergely, n. sp., D. ovatus Páll-Gergely & Auffenberg, n. sp., D. subroseus Páll-Gergely, n. sp., D. verrucosus Páll-Gergely & Hunyadi, n. sp., Metalycaeus anas Páll-Gergely & A. Reischütz, n. sp., M. aries Páll-Gergely & Auffenberg, n. sp., M. bicarinatus Páll-Gergely & Hunyadi, n. sp., M. pygmachos Páll-Gergely & Hunyadi, n. sp. Alycaeus kengtungensis Godwin-Austen, 1914 is moved to the synonymy of Metalycaeus heudei (Bavay & Dautzenberg, 1900). We also report exact localities of Dicharax ataranensis (Godwin-Austen, 1914), Dicharax notus (Godwin-Austen, 1914), and Dicharax omissus (Godwin-Austen, 1914). The new records extend the known distribution of Chamalycaeus and Metalycaeus in Thailand.

During systematic surveys of groundwater snails in Slovakia, Hungary and Bosnia and Hercegovina two new species of the genus Hauffenia , H. lozekiana sp. nov. from a single locality in Slovakia, and H. steffeki sp. nov. with a small range in Bosnia and Hercegovina were discovered and are here described based on shell morphology, anatomy and DNA sequence data (COI, 16S rRNA, ITS2). The discovery of H. steffeki sp. nov. extends the range of the genus considerably towards the south. Hauffenia lozekiana sp. nov. appears to be a relict surviving within the range of the today widely distributed H. kissdalmae. Based on a time tree, we developed a scenario for the origin and diversification of the genus. The ancestor probably evolved in the Miocene on the Balkans and with the gradual desiccation of the Paratethys and its remnant water bodies diversified towards the north. Karstic and in particular alluvial connectivities together with changing courses of paleo-rivers probably played an important role for dispersal. Ecological observations suggest that the phreatic rhizosphere, the delicate net of tree rootlets and their exudates, are important for the existence of these groundwater snails.

Since 2020, the south-western Caucasus has been recognized as a hotspot of stygobiotic Mollusca diversity after revealing a large number of new, range-restricted species within the spring snail family Hydrobiidae, subfamily Sadlerianinae sensu Szarowska. Meantime, based on extensive material collected in the south-western Caucasus during the last decades, we studied members of another spring snail subfamily Belgrandiellinae Radoman, 1983. Modern integrative taxonomic work revealed hitherto unknown diversity within this subfamily in the region and further proved the importance of the south-western Caucasus as a hotspot of stygobiotic life. In particular, the subterranean environment and springs of Georgia were known to be inhabited by the genus Tschernomorica Vinarski and Palatov, 2019 with four nominal species. Our research, based on a morpho-anatomical study and genetic investigation of COI/H3 mitochondrial/nuclear markers, revealed additionally seven species and three genera new to science—Colchiella lugella gen. et sp. nov., C. nazodelavo gen. et sp. nov., C. shiksa gen. et sp. nov., C. dadiani gen. et sp. nov., Sataplia cavernicola gen. et sp. nov., Aetis starobogatovi gen. et sp. nov., and Tschernomorica kopidophora sp. nov. —to inhabit the Georgian part of south-western Caucasus. The full taxonomic description of each new taxa, along with the review of habitat characteristics and conservation status, is provided. Molecular genetics suggests that the ancestors of Caucasian Belgrandiellinae have migrated from south-western Europe, probably more than once during the late Messinian and early Pliocene periods. Later, Plio-Pleistocene climate oscillations, particularly the repeated rise and fall of the Black Sea water level, resulted in the isolation and radiation of various lineages within the Caucasus and Crimea.