Zospeum tumidum Jochum, Schilthuizen & Ruthensteiner sp. nov. urn:lsid:zoobank.org:act: 1F6F1AB3-137B-4AA9-ABB8-46E0AF777F8C Fig. 10 Diagnosis Shell ca 1.5 mm, turbinate-conical with 5–5¼ regularly coiled, irregularly formed convex whorls; last coiling of shell twists a fraction beyond the frontal plane ca ⅛ the width of penultimate whorl; columella centrally aligned and moderately fat bearing a lamellar bulge rather than a fine lamella; umbilical depression deep. Etymology The species is named after the squat and wide, turbinate form of the shell. Type material Holotype MONTENEGRO • Piva Region, Bajovo Polje, Đokova pećina, at cave entrance; 43.0315° N, 18.8104° E; 1 Jul. 2018; M. Schilthuizen and I. Njunjić leg; at cave entrance; NMBE 572615 (ex TxEx-DU0025). Description MEASUREMENTS. Holotype: sh: 1.537 mm; sw: 1.177 mm; ah: 0.731 mm; aw: 0.712 mm; hlw: 1.028 mm; SA: 74.75 deg. Shell ca 1.5 mm, turbinate-conical with 5–5¼ irregular, flatly convex whorls; shell comparatively large; milky translucent; suture shallow with irregular indentations at the junction of the suture and the succeeding whorl growing into course growth lines; teleoconch sculpture of blunt irregular growth lines interspersed with fine, weak thread-like striations; distinct, fine, thread-like axial ribbing extends for a distance immediately behind palatal-basal lip; last whorl large and tumid, encompassing ca ⅔ of shell height; last coiling twists a fraction beyond the frontal plane ca ⅛ the width of body whorl; suture shallow; aperture reniform, somewhat higher than wide; peristome generally thin especially at upper palatal side, slightly expanded; weak notch present at upper junction with parietal shield, columellar side oblique and thickly callused, columellar and palatal-basal lip narrowly reflected; parietal shield well defined, straight, long, angular with course growth lines crossing into it; columella thick and centrally aligned, apically tapered (aperture facing right) with a lamellar bulge and no defined lamella; umbilical depression deep, callused and puckered; columellar side of peristome arches high over and oblique to umbilical depression, alignment of last ¼ whorl not compact. Distribution This species is only known from its type locality cave, Đokova pećina in the Bajovo Polje of Montenegro. Remarks The species is the only Southern Balkan species to possess a thick lamellar bulge. It has the widest shell with the greatest aperture height and aperture width as well as the highest last whorl and greatest spire angle of all 13 species (and one morphospecies Zospeum sp. 2) (encompassing 31 shells) measured in this study.

Published as part of Jochum, Adrienne, Michalik, Peter, Inäbnit, Thomas, Kneubühler, Jeannette, Slapnik, Rajko, Vrabec, Marko, Schilthuizen, Menno & Ruthensteiner, Bernhard, 2024, 3 D X-ray microscopy (Micro-CT) and SEM reveal Zospeum troglobalcanicum Absolon, 1916 and allied species from the Western Balkans (Ellobioidea: Carychiidae), pp. 1-62 in European Journal of Taxonomy 926 on pages 34-36, DOI: 10.5852/ejt.2024.926.2469, http://zenodo.org/record/10847806