Plectostoma mengaburensis, 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 : 32

Plectostoma mengaburensis sp. n. Figures 17E, 20, Appendix 7

Type material.

Holotype: BOR 5643(1). Paratypes: BOR 5574(>25), V8822 (6)

Diagnosis.

Shares with Plectostoma dindingensis and Plectostoma panhai the general shell form, in the terms of apex, spire and tuba, but differs by lacking constriction teeth and having a less tightly coiled tuba (more than 1/4 of the tuba visible in top view).

Etymology.

This species is named after its type locality–Mengabur.

Description.

Apex. Shape: moderately convex.

Spire. Height: 1.9-2.2 mm. Width: 1.4-1.6 mm. Number of whorls: 3 7/8-4 1/2. Apical spire shape: depressed conical. Basal spire shape: ovoid. Whorl periphery: distinctly convex. Umbilicus: open or half of the umbilicus closed by tuba.

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

Tuba. Coiling direction: type 1 and aperture visible from back view. Tuba whorl length in proportion to spire last whorl: ca. 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: 7 ribs per mm. Rib intensity: thin. Shape: straight. Inclination: orthoclin.

Distribution.

Type locality. An unnamed small limestone hill in the plantation near the large Bukit Mengabur quarry (3°43'50"N, 102°49'40"E).

Distribution range. This species only occurs in the Mengabur limestone cluster (Figure 18D).

Conservation status.

Near Threatened. This species only occurs in the Mengabur limestone cluster, which is quite large (ca. 10 km2, estimated from Google Earth), and its vegetation cover is largely undisturbed. However, quarrying activities have started at the eastern part of the cluster and the whole limestone cluster is surrounded by plantation.

Discussion.

See discussion under Plectostoma christae .