Plectostoma kayiani, 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 : 52-54

Plectostoma kayiani sp. n. Figure 36, Appendix 11

Type material.

Holotype: RMNH 330803 (1). Paratypes: V 8883(6), V 14243(1).

Etymology.

This species is named after Kay Arnold and Ian Mellsop from New Zealand, who have generously supported wildlife conservation work in many parts of Peninsular Malaysia, including the forests around Lake Kenyir where this species was discovered.

Diagnosis.

Shares with Plectostoma ikanensis the general shell form, in terms of spire and tuba shape, but differs by lacking thick spiral lines.

Description.

Apex. Shape: slightly to moderately convex.

Spire. Height: 1.4-1.6 mm. Width: 1.2-1.4 mm. Number of whorls: 3 1/2-3 3/4. Apical spire shape: depressed conical. Basal spire shape: conical. Whorl periphery: distinctly convex. Umbilicus: open.

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

Tuba. Coiling direction: type 2 and aperture visible from front view. Tuba whorl length in proportion to spire last whorl: ca. 5/8-3/4. Proportion of tuba that attaches to spire: almost whole except the part near the aperture.

Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similer to inner peristome, projected all around, except the posterior part, where left lateral sides are slightly more projected than the anterior and right lateral side.

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

Radial ribs. Rib density: 8-10 ribs per mm. Rib intensity: thin. Shape: slightly curved. Inclination: orthoclin.

Distribution.

Type locality. Gua Bewah, Tasik Kenyir (4°51'3"N, 102°43'21"E).

Distribution range. To date, this species is only known to occur at two neighbouring limestone outcrops, namely, Gua Bewah and Gua Taat at the southern part of Tasik Kenyir (Figure 18C).

Conservation status.

Least concern. The outcrops where this species is found, are partially submerged in Southeast-Asia’s largest man-made lake, Tasik Kenyir. Despite this, there is a good forest cover around and on the limestone outcrops. Furthermore, these two hills are located in a protected National Park.

Discussion.

This species occurs sympatrically with Plectostoma tohchinyawi and Plectostoma whitteni .