Tricula davisi, 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 : 23

Tricula davisi sp. n. Figs 29-32

Type locality.

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

Type material.

Holotype: type locality: J. Grego and M. Olšavský leg. 11-12 February 2017 (NHMUK 20180009). Paratypes: type locality (NHMUK 20180022 - 3 specimens; HNHM 102775 - 3 specimens; OSUM 42387 - 3 specimens; coll. Grego F0878 - 76 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 F0858 - 6 specimens) (Fig. 2A).

Measurements.

Holotype: H 2.72 mm; W 1.81 mm; BW 1.23 mm; BH 1.88 mm; AH 1.5 mm; AW 1.05 mm; H/W 1.50; AH/AW 1.29; W/BW 1.47; H/BH 1.45; H/AH 2.01; W/AW 1.72.

Diagnosis.

This new species is similar to syntopic Tricula lenahani sp. n., from which it differs by its more oval, inflated shell with more inflated whorls, a closed umbilicus and the shape of the aperture. The aperture of T. davisi sp. n. has a characteristic sinuation at the columellar peristome and a straight labral peristome, distinguishing it from T. lenahani sp. n., which has a sinuated labral peristome and a different columellar peristome, as well from the syntopic T. spelaea sp. n., the peristome of which lacks significant sinuation on both sides. From T. bollingi Davis, 1968 and T. burchi Davis, 1968 it differs by its shell and aperture shapes.

Description.

The shell is rounded oval-conical with four slightly inflated whorls with elevated spire and a deeper suture. The surface is milky whitish and smooth with faint growth lines. The aperture is oval ear-shaped, the peristome slightly callous attached to the body whorl and expanding only towards the columella. The labral lip lateral profile is straight, while a characteristic deep sinuation is present at the apical inner lip. The last whorl is broadening towards the aperture and from lateral view is curved upward. The umbilicus is closed.

Etymology.

Named after George M. Davis, (Washington D.C., USA) who contributed much to the molecular phylogeny and taxonomy of the Mekong River Pomatiopsidae .

Distribution.

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

Ecology.

The same as Pseudoiglica pseudoiglica sp. n.