Shares with Plectostoma charasense, Plectostoma tohchinyawi, and Plectostomaklongsangensis the general shell form, in terms of apex, spire, and tuba shape, but differs by lacking thick spiral lines and basal constriction teeth.
BOR 1697(>10). YSC.
Apex. Shape: distinctly convex.
Spire. Height: 2.9–3.0 mm. Width: 1.7–1.8 mm. Number of whorls: 5 5/8–5 3/4. Apical spire shape: oblong conical. Basal spire shape: conical. Whorl periphery: distinctly convex. Umbilicus: partially closed by tuba.
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. 3/4–7/8. Proportion of tuba that attaches to spire: less than 2/3.
Aperture and peristome. Peristome: double peristomes. Outer peristome shape: similar to inner peristome, projected all around, except the posterior part, where the two lateral sides are slightly more projected than the anterior side.
Spiral lines. Thick lines: absent. Thin lines: present.
Radial ribs. Rib density: 5–6 ribs per mm. Rib intensity: thin. Shape: slightly curved. Inclination: orthoclin.
Data deficient. This species has only been recorded from three limestone hills in West Sumatra. The population status and actual distribution range of this species remain unknown. Nevertheless, concern is warrented, as the surroundings of the type locality and several other limestone outcrops in the same area are highly degraded.
Holotype: RMNH 92942(1) (seen). Paratypes: RMNH 92956(>25) (Seen), V 12697(9) (Seen).
Type locality. Cave Pangian (local name Ngalau Pangian - 0°27'45"S, 100°45'8"E)
Distribution range. This species was also found at a limestone hill near Kampung Desa Gadut, West Sumatra (0°15'36"S, 100°44'16"E). This hill is located about 20 km from the type locality. In addition, a private collector (Yansen Chen, pers. comm.) also collected the same species at Tiangko cave, about 230 km from the type locality (Figure 18B). It therefore appears to have a wide distribution range in Sumatra. It may thus be expected that the limestone outcrops around the three hills mentioned, might support the same species.
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There are large areas in the Northern and Western provinces of Sumatra that are covered by limestone hills (Verstappen and Genootschap 1973). Despite intensive malacological surveys in some of these areas (van Benthem Jutting 1959), no Plectostoma species was found until 1997. To date, Plectostoma kitteli is the only Plectostoma species found in Sumatra (Maassen 2002).
Kampung Desa Gadut, limestone rocks near the village. West Sumatra, Indonesia.
By Maassen (2002)
"shell conical, sinistroid, with flat to slightly convex sides. Apex slightly oblique sometimes. Whorls 6 1/2, convex; last whorl rounded. Constriction with a parietalis, and both a longitudinal and transversal palatalis; a columellaris is absent. Tuba abruptly narrowed towards the constriction, (slightly_ angular below. Apical whorls smooth; the following ones with very sharp radial ribs, which are rather widely spaced (7-8 ribs/1mm on the penultimate whorl). The ribs on the tuba moderately to widely spaced (6-7 ribs/ 1mm haldway the tuba); on the spire and on the tuba slightly sinuous. Spiral striation absent. Umbilicus open, measuring 0.1 mm in diameter. Aperture hardly tilted with regard to the coiling axis, more or less circular to elliptic. Peristome double. Outer peristome spreading far beyond the inner one, but distinctly so only at the parietal and the basal side; absent along the right side of the aperture. Inner peristome distinctly protruding from the outer one for about 0.3 mm, slightly spreading. Dimensions: H 2.8-3.1 mm, B 1.5-1.6 mm (without tuba); B 2.4-2.6 mm with tuba."
