A cybertaxonomic revision of the micro-landsnail genus Plectostoma Adam (Mollusca, Caenogastropoda, Diplommatinidae), from Peninsular Malaysia, Sumatra and Indochina Author Liew, Thor-Seng Author Vermeulen, Jaap Jan Author Marzuki, Mohammad Effendi bin Author Schilthuizen, Menno text ZooKeys 2014 393 1 107 http://dx.doi.org/10.3897/zookeys.393.6717 journal article http://dx.doi.org/10.3897/zookeys.393.6717 1313-2970-393-1 5B035E76BBD14A44A5D8C2140E6168F1 5B035E76BBD14A44A5D8C2140E6168F1 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. Figures 38. Plectostoma relauensis sp. n. BOR 5511. A frontal view B left lateral view C back view D right lateral view E top view F bottom view G parietal part of constriction inner whorl H basal part of constriction inner whorl. Scale bar = 1 mm (for A-F ). 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).