Plectostoma laidlawi (Sykes, 1902)
Look alikes:
Opisthostoma pumilio
Habitat:
On the limestone surface covered with wet mosses.
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Plectostoma laidlawi (Sykes, 1902)
Plectostoma laidlawi (Sykes, 1902)
General description:to be added
Conservation status:to be added
Diagnostic description:Holotype: Not Seen. Paratype: ZMA 136014(1) (Seen).
Taxon biology:The morphology of this species is quite variable in shell size and degree of attachment of the tuba to the spire. The distribution range partially overlaps with that of Plectostoma davisoni. It is possible that the species actually consists of two or more cryptic species, and thus more genetic data are needed.
Distribution:Type locality. “Kelantan, Malay Peninsula”, collected by J. Waterstradt (Sykes 1902). According to Waterstradt’s (1902) itinerary, he visited one of the limestone hills at Kampung Pulai. The Pulai Princess cave (4°47'38"N, 101°56'31"E) fits perfectly with Waterstradt’s descriptions on the local population, temples and hill’s topography; he also described that he and his collectors sampled shells here (Waterstradt 1902: 9–10). We conclude that Pulai Princess Cave must be the type locality of Plectostoma laidlawi. However, a recent survey at the highly degraded Bukit Pulai Princess cave failed to retrieve any shells of Plectostoma.
Distribution range. This species occurs on the limestone hills along Berok River and Nenggiri River (Figure 18B).
Plectostoma laidlawi (Sykes, 1902)
General description:Apex. Shape: moderately to distinctly convex.
Spire. Height: 1.6–2.3 mm. Width: 1.3–1.8 mm. Number of whorls: 3 5/8–4. Apical spire shape: depressed conical. Basal spire shape: conical to ovoid. Whorl periphery: 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: varies from completely attached to as much as half of the tuba detached from spire.
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 or left lateral sides slightly more projected than the anterior and right lateral side.
Spiral lines. Thick lines: present. Thin lines: present.
Radial ribs. Rib density: 5–6 ribs per mm. Rib intensity: thin. Shape: straight to slightly curved. Inclination: moderately prosoclin.
Conservation status:Vulnerable (D2 ver. 10.1). Living populations were present on only two limestone hills during a survey in May 2011. All the limestone hills for which this species is known are surrounded by degraded forest and oil palm plantation.
Diagnostic description:BMNH C_ACC1825(1), BOR 5510(>25), BOR 5571(2), RMNH 156268(1), ZMA 162095(2), ZMA 162097(>25), ZMA 162099(>10), ZMA 162100(>25), ZMA 162096(1), V5558(1), V 7878(3), V 8345(>100), V 8476(>25), V 8670(>25), V 8693(>50), V 8950(>50), V 9044(>25), V 9109(>25), V 9125(>25), V 9359(6).
Plectostoma laidlawi (Sykes, 1902)
Diagnostic description:Shares with Plectostoma annandalei, Plectostoma tenggekensis, and Plectostoma praeco the general shell form in terms of spire and tuba shape, but differs by having a distinctly convex whorl periphery and straight ribs.
Plectostoma laidlawi (Sykes, 1902)
Diagnostic description:“Recalls in form several of the Bornean species, but the apex is much depressed, the shell is not so pyramidal, and the whorls very conic.” (Sykes, 1902)
Morphology:Sykes (1902) original descriptions on Opisthostoma laidlawi – “Shell ovate-conic, pale reddish horn-colour, apex obtuse; whorls 6-6 ½, strongly convex, the lower ones being regularly, but finely and somewhat distantly, marked with lamellae. The last whorl is solute, rounded, and bent backwards nearly to the suture of the fourth whorl.”
Size:Opisthostoma laidlawi – “Alt. 2; diam. max. 2.5; diam. Min. 1.5 millim.” (Sykes, 1902)
Distribution:Type locality – “Kelantan, Malay Peninsula” leg. J. Waterstradt (Sykes, 1902)
In Waterstradt (1902)'s itinerary, he visited one of the limestone hill at Kampung Pulai. The Pulai Princess cave (name in mandarin 紫霞洞 Zi Xian Tong) 4°47'38.18"N 101°56'31.45"E (http://pulai.org/cave.html) fits perfectly with Waterstradt's descriptions on the local population, temples and hill's topography (page 9-10). More importantly, he and his collectors sampled shell from here (Page 10). Thus, Pulai Princess cave is the type locality of Plectostoma laidlawi.
Waterstradt, J.1902 'Kelantan and my trip to Gunong Tahan', Journal of the Straits Branch of the Royal Asiatic Society 37, Pt. 4: 1-27.
other location: Kelantan, Malaysia.; Bukit Ciku 4, Felda Ciku, Gua Musang, Kelantan, Malaysia.