Philalanka tambunanensis Vermeulen, Liew & Schilthuizen

Vermeulen, Jaap J., Liew, Thor-Seng & Schilthuizen, Menno, 2015, Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species, ZooKeys 531, pp. 1-139 : 50-51

Taxon classification Animalia Stylommatophora Endodontidae

Philalanka tambunanensis Vermeulen, Liew & Schilthuizen sp. n. Figure 42

Holotype. Malaysia, Sabah, Interior Province , Gunung Trusmadi slopes , Gua Loloposon ( RMNH.5003938 ).

Examined material from Sabah.

Interior Province. Upper Padas valley, Long Pasia (leg. T.S. Liew & Meckson, BOR/MOL 4340). Crocker Range N.P., West of the km 10 marker on the road Tambunan-Ranau, Mahua Waterfall (leg. J.J. Vermeulen & M. Schilthuizen, V 14250; leg. M. Schilthuizen, BOR/MOL 2317). Gunung Trusmadi slopes, Gua Loloposon (leg. J.J. Vermeulen, V 13221).

Description.

Shell very small, thin, translucent to opaque, pale brown- or yellow-corneous to white, conical with flat or slightly convex sides; apex widely rounded. Surface with a silky luster. Whorls convex, rounded. Protoconch whorls convex; sculpture: 10-15 rather distinct, thin spiral threads; radial sculpture approx. absent or some very fine, subordinate wrinkles. Teleoconch: Last whorl with (1-)2 inconspicuous to distinct, narrow spiral threads (1 above the periphery, sometimes absent; 1 below the periphery, coinciding with the suture of the penultimate whorl); next to these a distinct, fine, rather dense spiral striation present, sometimes less conspicuous just below the suture; below the lowermost spiral thread the spiral striation is (somewhat) more widely spaced and gradually disappears towards the umbilicus. Radial sculpture most distinct below the suture: fine growth lines grading into rather densely placed, rather distinct riblets; the interstices between these riblets cut into the crests of the spiral striation. Umbilicus open, rather narrow. Dimensions: Height up to 2.3 mm; width up to 2.5 mm; diameters of the first four whorls 0.55-0.80 mm, 0.95-1.20 mm, 1.45-1.80 mm, 2.0-2.3 mm respectively; number of whorls up to 5; height aperture up to 1.0 mm; width aperture up to 1.3 mm.

Habitat in Sabah and distribution.

Damp primary forest around streams, on limestone and sandstone bedrock, 500-1000 m alt. Sabah: Upper Padas River, Tambunan valley. Endemic to Sabah.

Cross diagnosis.

Differs from Philalanka kusana by the more distinct spiral striation next to the two threads, as well as a more distinct radial sculpture. As a result, the shell is not shiny, but has a silky luster. Philalanka tambunanensis usually has two spiral threads; Philalanka kusana usually has three, sometimes two.

Philalanka carinifera (Stoliczka), from Peninsular Malaysia, is more densely coiled (diameters of the first four whorls 0.4-0.5 mm, 0.70-0.85 mm, 1.05-1.20 mm, 1.4-1.6 mm respectively), and has a shiny surface with inconspicuous sculpture only, apart from the spiral threads.

Etymology.

The name refers to the area where the species is found.