Thamkhondonia smidai, Grego, Jozef, 2018

Grego, Jozef, 2018, First record of subterranean rissoidean gastropod assemblages in Southeast Asia (Mollusca, Gastropoda, Pomatiopsidae), Subterranean Biology 25, pp. 9-34 : 18-20

Thamkhondonia smidai sp. n. Figs 19-22

Type locality.

Laos; Khammouane Province, Ban Na village 20 km NNE of Thakhek, Tham Khon Dôn Cave 17°33.82'N; 104°52.30'E, 161 m a.s.l., Earthquake Dome 3 km from the south entrance, sand sediments at cave river bank (Fig. 2B).

Type material.

Holotype: type locality: J. Grego and M. Olšavský leg. 11-12 February 2017 (NHMUK 20180007). Paratypes: type locality (NHMUK 20180020 - 2 specimens; HNHM 102773 - 2 specimens; OSUM 42383 - 2 specimens; coll. Grego F0876 - 34 specimens); Laos, Khammouane Province, 3 km NW of Ban Na Village, sand on the bottom of Nam Dôn river source at 149 m a.s.l.; J. Grego leg. 07 February 2017, 17°33.20'N; 104°52.38'E (coll. Grego F0902 - 2 specimens) (Fig. 2A).

Measurements.

Holotype: H 3.62 mm; W 1.45 mm; BW 1.15 mm; BH 1.45 mm; AH 1.05 mm; AW 0.75 mm; H/W 2.50; AH/AW 1.15; W/BW 0.36; H/BH 2.16; H/AH 3.45; W/AW 1.59. Paratype 1: H 3.45 mm; W 1.38 mm; BH 1.10 mm; BW 150; AH 1.00 mm; AW 0.87 mm; H/W 2.50; AH/AW 1.15; W/BW 0.36; H/BH 2.18; H/AH 3.45; W/AW 1.59.

Diagnosis.

Thamkhondonia smidai sp. n. differs from syntopic T. moureti sp. n. by its smaller shell with less coarse and more numerous spiral sculpture and from T. vacquiei sp. n. (syntopic) by its longer and more slender shell shape with coarser spiral cords.

Description.

The whitish translucent, elongate shell has seven convex whorls with a weakly wavy suture. The shell surface sculptured by 5-6 spiral cords crossed by very fine axial ribs. The oval ear-shaped aperture has a weak posterior canal and extends slightly beyond the shell periphery outline; the peristome is blunt and reflexed at the columellar side. The lateral edge of the labral lip is weakly sinuated and an axial varix is present parallel to the labral lip. The umbilicus is closed.

Etymology.

Named after the famous Slovak speleologist Branislav Šmída, Bratislava, Slovakia, who actively participated in our 2017 biospeleology survey of Laos.

Distribution.

Only known from the type locality and nearby sites in Tham Khon Dôn Cave as well as in the related source of Nam Dôn River.

Ecology.

The same as Pseudoiglica pseudoiglica sp. n.

Remark.

The shell morphology of T. smidai sp. n. is an intermediate between that of T. moureti sp. n. and T. vacquiei sp. n.