Plectostoma praeco (van Benthem Jutting, 1961)

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 : 68-69

Plectostoma praeco (van Benthem Jutting, 1961) Figure 46, Appendix 14

Opisthostoma praeco van Benthem Jutting, 1961: 39, Plate 2 - figure 5 (original description).

Type material.

Holotype: ZMA 136034(1) (Seen). Paratypes: ZMA 136041(>50) (Seen), ZMA 136042(>25) (Seen).

Other examined materials.

ZMA 162150(>100), ZMA 162151(>100), ZMA 162152(>100), ZMA 162153(>10).

Diagnosis.

Shares with Plectostoma laidlawi , Plectostoma tenggekensis , and Plectostoma annandalei the general shell form, in terms of spire and tuba shape, but differs by having slightly curved ribs.

Description.

Apex. Shape: distinctly convex.

Spire. Height: 2.0-2.2 mm. Width: 1.8-2.0 mm. Number of whorls: 4 1/4-4 5/8. Apical spire shape: depressed conical. Basal spire shape: conical. Whorl periphery: moderately to distinctly convex. Umbilicus: open.

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

Tuba. Coiling direction: type 2 and aperture visible in right lateral view. Tuba whorl length in proportion to spire last whorl: ca. 5/8-7/8. Proportion of tuba that attaches to spire: more than 1/3 but less than 1/2.

Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similar to inner peristome, projected all around, except the posterior part, where the 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: 6-7 ribs per mm. Rib intensity: thin. Shape: slightly curved. Inclination: moderately prosoclin.

Distribution.

Type locality. Batu Che Derani, Taman Negara Pahang (4°35'57"N, 102°25'57"E).

Distribution range. Plectostoma praeco has been recorded from four other hills at upper Sungai Keniyam Kecil, which is in the vicinity of the type locality (Figure 18B).

Conservation status.

Least concern. All the limestone hills where Plectostoma praeco occurs, are located in the National Park.

Discussion.

There is no genetic information for Plectostoma praeco . Morphological similarity suggests that Plectostoma praeco and Plectostoma tenggekensis are closely related. Each of the two species has a narrow distribution range and they are separated from each other by at least 50 km.