Hausdorfenia shareula 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

Hausdorfenia shareula Grego & Mumladze sp. nov. Plate 20 (5)

Type locality.

Georgia • Racha, Nikortsminda, Tsivtskala 2 Spring on left bank of the Shareula River near the power station; 42°28'18"N, 43°03'54"E; 1084 m a.s.l.

Material.

Holotype: Georgia • 1 adult, dry; type locality; 06 May 2018; J. Grego, L. Mumladze and M. Olšavský leg.; ISU FM-T012-H. Other material: Georgia • Fragmented shells; Racha, Nikorsminda, Shareula River Head (Shareula Cave); 42°28'12"N, 43°04'4"E; 1105 m a.s.l.; date; 20.08.2017, J. Grego leg.

Diagnosis.

The new taxon significantly differs from all congeners by its flat shape with spire hidden in apertural profile and its planorboid coiling, a unique feature within the southwestern Caucasus stygobiotic Gastropoda. Measurement comparison of Pontohoratia and Hausdorfenia species is given in Table 9 .

Description.

Shell: planispiral, discoid with planorboid (slightly hyperstrophic) coiling and 1.34 mm in diameter. Descending 2¼ whorls separated by a deep suture. Umbilicus very widely expanding. Shell colour milky white, surface smooth with very faint axial growth lines. Aperture circular, and its labral periphery is oblique to the columellar axis. It attached to the whole length of the adjacent body whorl by a narrow suture. Protoconch pitted over whole surface.

Operculum: not known.

Animal body: not known.

Holotype measurements: H-0.53 mm; W-1.34 mm; BH-0.50 mm; BW-0.82 mm; AH-0.48 mm; AW-0.42 mm; CA: -57°.

Anatomy: not known.

Etymology.

Name derived from the name of the Shareula River (მდინარე შარეულა), left tributary of the Rioni River, in which valley and a nearby tributary the new taxon was found.

Habitat.

The intact empty shell was found in sandy sediment at the spring head in a small cave. The supposed habitat is stygobiotic.

Distribution.

Except the type locality few similar fragments were found at the Shareula River Head (entrance of Shareula 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.

Hausdorfenia pseudohauffenia sp. nov. and P. shareula sp. nov. display shell features different from other members of the genus, as well as a characteristic operculum with a peg (at least in the former taxon). Both represent a new genus different from Pontohoratia .

Figures

Plate 20. 1, 2 Pontohoratia vinarskii sp. nov., Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave: 1 holotype 2 paratype 3 P. pichkhaiai sp. nov., Samegrelo, Mukhuri, Shisha Spring, holotype 4 Hausdorfenia pseudohauffenia sp. nov., Racha, Zemo Krikhi, Krikhula Spring, holotype 5 H. shareula sp. nov., Racha, Nikortsmintha, Tsivtskala 2 Spring near power station in the Shareula valley, holotype 6 P. mapeli sp. nov., Samegrelo, Mukhuri, Kanti, Mapeli Spring, holotype 7 H. pseudohauffenia sp. nov., Racha, Zemo Krikhi, Krikhula Spring; aberrant specimen 8, 9 P. vinarskii sp. nov., Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave: 8 morphotype 9 live specimen with marked carbonate incrustations. The numbers correspond to individuals, and the letters represent the different views of the same individual. Photograph J. Grego.