Plectostoma sciaphilum (van Benthem Jutting, 1952)

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 : 43

Plectostoma sciaphilum (van Benthem Jutting, 1952) Figure 29, Appendix 7

Opisthostoma sciaphilum van Benthem Jutting, 1952: 45, figure 23 (original description).

Type material.

Holotype: ZMA 136049(1) (Seen). Paratypes: ZMA 136050(>10) (Seen).

Diagnosis.

Shares with Plectostoma senex and Plectostoma turriforme the tuba form, but differs by lacking basal constriction teeth.

Description.

Apex. Shape: distinctly convex.

Spire. Height: 2.6-2.9 mm. Width: 1.5-1.6 mm. Number of whorls: 4 1/4-5 1/2. Apical spire shape: oblong conical. Basal spire shape: ovoid. Whorl periphery: distinctly convex. Umbilicus: completely closed by tuba.

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

Tuba. Coiling direction: type 3 and aperture visible in left lateral view. Tuba whorl length in proportion to spire last whorl: ca. 3/8. 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: 6-8 ribs per mm. Rib intensity: thin. Shape: slightly curved.

Distribution.

Type locality. Bukit Panching, Pahang (3°53'28"N, 103°8'26"E).

Distribution range. Endemic to Bukit Panching (not seen in Figure 18A because its symbol overlaps with Plectostoma senex ).

Conservation status.

Extinct. Its only habitat–Bukit Panching, has been completed quarried away (see also Schilthuizen and Clements 2008). The ruin is now inundated. The status of this species in a previous assessment (IUCN redlist) was: Critically Endangered B2ab(ii,iii) ver. 3.1 ( Clements 2009a).

Discussion.

See under Plectostoma turriforme .