Caucasopsis cf. egrisi, Grego & Mumladze, 2020

Grego, Jozef, Mumladze, Levan, Falniowski, Andrzej, Osikowski, Artur, Rysiewska, Aleksandra, Palatov, Dimitry M. & Hofman, Sebastian, 2020, 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, ZooKeys 955, pp. 1-77 : 1

Caucasopsis cf. egrisi

Other material.

Georgia • Samegrelo, Pirveli Balda, Motena Cave; 42°28'36"N, 42°23'29"E; 480 m a.s.l.; 09 May 2018; J. Grego, L. Mumladze and M. Olšavský leg.; coll. ISU FM-HYD1/2 dry and JG/3 dry.

Diagnosis.

The new species shows some similarity to the geographically isolated C. olsavskyi sp. nov. from Nazodelavo Cave near Chkhorotsku, but it differs by its by its more oval, elongate shells shape with proportionally larger body whorl, by larger and differently positioned aperture situated more left of the columella (to viewer; shell in apertural pose, apex up) and by the more closed umbilicus. Measurement comparison of Caucasopsis species is given in Table 6 .

Description.

Shell: narrow elongate-oval, 1.66-2.00 mm high with 4½ slightly tumid whorls, blunt protoconch, and weak suture. Shell surface whitish and smooth with faint axial growth lines, covered by milky white periostracum and by inorganic incrustations. Aperture proportionally smaller vs. the body whorl and more close-set to the columellar axis. The peristome attached to the body whorl by a weak sulcus over approximately a quarter of its outline. Lateral and columellar labral profiles smooth-straight with no traces of any sinuation. Umbilicus closed.

Operculum: not known.

Animal body: not known.

Holotype measurements: H-2.00 mm; W-0.91 mm; BH-1.19 mm; BW-0.81 mm; AH-0.64 mm; AW-0.51 mm; CA: 34°.

Anatomy: not known.

Etymology.

Named after Egrisi (ეგრისი), the historical name of the Colchis Kingdom established in the region from the 13th to the 1st century BC (disestablished in 164 BC).

Habitat.

Stygobiotic species. The secondary position where the empty shells of the new species were found is the spring head of small springs in village Pirveli Balda emerging from the stone debris at foot of the limestone plateau. The primary subterranean habitat is inaccessible and unknown.

Distribution.

Only known from the type locality; the similar shells can be found in a nearby Motena Cave.

Conservation status.

The number of known locations (2) 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.

Remarks.

The assignment of the new species to the genus Caucasopsis gen. nov. is only provisional, based on the sinuated lateral labral profile and on the locality, situated close to the distribution range of Imeretiopsis gen. nov. The molecular data will be essential to assign the species to the correct genus. The population in Motena Cave has slightly different shell morphology, and, despite their close localities, both represent different hydrological systems (perched water tables) separated by horizontal impermeable sandstone beds with more than 100 m difference in altitude. It is possible both populations could show separation at the species level; however, we prefer provisionally to treat them as one species until molecular data become available.