Sitnikovia, Chertoprud & Palatov & Vinarski, 2020

Chertoprud, E. M., Palatov, D. M. & Vinarski, M. V., 2020, Revealing the stygobiont and crenobiont Mollusca biodiversity hotspot in Caucasus: Part II. Sitnikovia gen. nov., a new genus of stygobiont microsnails (Gastropoda: Hydrobiidae) from Georgia, Zoosystematica Rossica (China) 29 (2), pp. 258-266 : 260

Genus Sitnikovia gen. nov.

Type species Sitnikovia megruli sp. nov.

Diagnosis. Shell high-conical, relatively slen- der (SW/SH ratio 0.40–0.60), with four to six slowly increasing whorls. Spire high, body whorl moderately inflated. Operculum ovate, corneous, thin and flat, without protrusions on the inner side, paucispiral with submarginal nucleus, usually orange or yellowish. Animal blind. Inner callus not developed. Radula of taenioglossate type, with formula 5-1-5-1-1; central (or rachidi- an) tooth with single pair of basal cusps. Lateral tooth resembles rachis in its shape and position of cusps, and bears eight or nine cusps (three or four at inner side, one largest, four at outer side); inner marginal tooth with 21–24 cusps, outer marginal tooth with 16 cusps.

Penis with a single dorso-lateral lobe, whose appearance varies from a well-developed conical offshoot to massive bulging with small knobby tip. The distal part of the penis is narrow and pointed; in its central part the penis is swollen; its width slowly decreases towards the basal part.

From all genera of the Caucasian hydrobiid snails, established to the date, Sitnikovia gen. nov. differs by a unique combination of general shell shape and the penis structure.

Etymology. Named after Dr. Tatiana Ya. Sitnikova, a renowned Russian expert in systematics of the freshwater Caenogastopoda.

Species composition. Sitnikovia gen. nov. includes two species described herein, both are endemic to Georgia.