Plectostoma relauensis, Liew, Thor-Seng, Vermeulen, Jaap Jan, Marzuki, Mohammad Effendi bin & Schilthuizen, Menno, 2014

Liew, Thor-Seng, Vermeulen, Jaap Jan, Marzuki, Mohammad Effendi bin & Schilthuizen, Menno, 2014, A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina, ZooKeys 393, pp. 1-107 : 55-56

Plectostoma relauensis sp. n. Figures 17P, 38, Appendix 13

Type material.

Holotype: BOR 5647(1). Paratypes: BOR 463(2), BOR 5511(>25), V 8169(9).

Etymology.

This species is named after its type locality–Relau substation of Taman Negara, where Gua Gajah is located.

Diagnosis.

Shares with Plectostoma davisoni the general shell form, in terms of apex, spire, and tuba shape, but differs by having a single parietal constriction tooth.

Description.

Apex. Shape: slightly to moderately convex.

Spire. Height: 1.5-1.9 mm. Width: 1.5-1.6 mm. Number of whorls: 3 3/8-3 5/8. Apical spire shape: depressed conical. Basal spire shape: ovoid. Whorl periphery: moderately to distinctly convex. Umbilicus: open.

Constriction. Parietal teeth: one. Basal teeth: none.

Tuba. Coiling direction: type 2 and aperture visible in frontal view. Tuba whorl length in proportion to spire last whorl: ca. 1/2-5/8. Proportion of tuba that attaches to spire: whole.

Aperture and peristome. Peristome: double peristomes. Outer peristome shape: same as inner peristome and uniformly projected all around, except the posterior part.

Spiral lines. Thick lines: present. Thin lines: present.

Radial ribs. Rib density: 4-7 ribs per mm. Rib intensity: thin. Shape: straight to slightly curved. Inclination: orthoclin.

Distribution.

Type locality. Gua Gajah in the Relau substation, Taman Negara. (4°38'15"N, 102°3'50"E).

Distribution range. This species also occurs at a limestone hill located about 20 km north of the type locality. BOR 463 was collection in Pulau Singa Besar, which is located about 300 km from type locality. The reliability of the collection data is dubious (see also BOR 462 of Plectostoma sinyumensis ).

Conservation status.

Least Concern. A large living population of Plectostoma relauensis was found at Gua Gajah, which is located in the National Park.

Discussion.

This species occurs sympatrically with Plectostoma siphonostomum on the same limestone hills. Despite the high density of limestone hills in the area, where many other Plectostoma species occur, Plectostoma relauensis is only found in two of these (Figure 18).