Plectostoma crassipupa (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 : 39-40

Plectostoma crassipupa (van Benthem Jutting, 1952) Figures 17I, M, 26, Appendix 6

Opisthostoma crassipupa van Benthem Jutting, 1952: 51, figure 26 (original description).

Opisthostoma crassipupa van Benthem Jutting, van Benthem Jutting (1961: 39).

Opisthostoma crassipupa van Benthem Jutting, Clements (2007: 74).

Opisthostoma crassipupa van Benthem Jutting, Clements et al. (2008: 2760).

Type material.

Holotype: ZMA 135994(1) (Seen). Paratype: ZMA 135993(>50) (Seen).

Other examined materials.

BOR 5512(>50), BOR 5515(2), BOR 5624(>10), BOR 5629(3), V 8392(>10), V 8407(10), V 8408(4), V 8437(>10), V 8898(7). V 8912(1), V 8956(1), V 9097(9), V 9157(>10), V 9326(>10), V 9353(3), V 9366(10).

Genetic distance between BOR 5512 and BOR 5515 is 14%.

Diagnosis.

Shares with Plectostoma sciaphilum , Plectostoma senex , and Plectostoma turriforme the tuba form, but differs by having a slightly or moderately convex apex and depressed apical spire.

Description.

Apex. Shape: slightly or moderately convex.

Spire. Height: 1.3-3.0 mm. Width: 1.2-1.4 mm. Number of whorls: 3 1/2-4 1/2. Apical spire shape: depressed conical. Basal spire shape: ovoid. Whorl periphery: moderately or distinctly convex. Umbilicus: closed by tuba (common) or partially open (rare).

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

Tuba. Coiling direction: type 3 and aperture visible from left lateral view. Tuba whorl length in proportion to spire last whorl: ca. 1/2-3/4 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: straight. Inclination: moderately prosoclin.

Distribution.

Type locality. Gua Musang (4°52'59"N, 101°58'12"E).

Distribution range. This species mainly occurs in the limestome hills that are located between Gua Musang and as far as 30 km radius of Gua Musang. One populations exists at a limestone hill that is located about 90 km north of Gua Musang (Figure 18A).

Conservation status.

Least Concern. Almost all the limestone hills are located along main roads and/or surrounded by oil palm plantation or cleared for urban development. However, several large limestone hills that hold the species are located in the well-protected National Park (Taman Negara), State of Pahang, Malaysia.

Discussion.

The species is well-characterised, although it displays considerable variability in the shell shape (Appendix 6).