Philalanka rugulosa 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 : 59-60

Taxon classification Animalia Stylommatophora Endodontidae

Philalanka rugulosa Vermeulen, Liew & Schilthuizen sp. n. Figure 48

Holotype. Malaysia, Sabah, West Coast Province , Kinabalu N.P. , summit trail ( RMNH.5003941 ).

Examined material from Sabah.

West Coast Province. Kinabalu N.P., Summit trail between 2984 and 4080 m (leg. T.S. Liew, BOR/MOL 4197, BOR/MOL 4198, BOR/MOL 4199, BOR/MOL 4200, BOR/MOL 4201, V 14339, V 14340, V 14341).

Description.

Shell very small, very thin, hardly translucent, yellowish brown, (low) conical with slightly convex sides; apex rounded. Surface with a silky luster. Whorls convex above and below the periphery, periphery rounded to slightly angular (in adults, more distinctly angular in juveniles, suture somewhat impressed. Protoconch whorls moderately convex; almost smooth with the slightest traces of a radial sculpture, and a very fine, dense spiral striation. Teleoconch: last whorl sometimes with a thin, inconspicuous peripheral thread coinciding with the suture of the penultimate whorl; some traces of a fine, dense spiral striation below this thread. Radial sculpture: rather distinct, irregularly spaced, somewhat raised growth lines, grading into more regularly and rather densely placed, low riblets; towards the umbilicus the growth lines tend to become less conspicuous. Umbilicus open, narrow. Dimensions: Height up to 2.7 mm; width up to 3.4 mm; diameters of the first three whorls 0.65-0.75 mm, 1.2-1.4 mm, 2.25-2.60 mm respectively; number of whorls up to c. 4 1/4; height aperture up to 1.5 mm; width aperture up to 1.75 mm.

Habitat in Sabah and distribution.

Subalpine vegetation on granodiorite soil. Alt. 2900-4100 m. Sabah: Mount Kinabalu (summit trail area). Endemic to Sabah.

Cross diagnosis.

Distinctly larger than Philalanka anomphala and Philalanka malimgunung ; from the first it also differs by having an umbilicate shell.

Philalanka lieftincki Van Benthem Jutting, 1953 (Indonesia, Ambon) looks similar but is smaller (shell 1.5-1.9 mm high, at 4-4 1/2 whorls). Philalanka micromphala Van Benthem Jutting, 1952 (Indonesia, Java) is of similar shape and size, but has a more angular last whorl with a distinct peripheral thread, a finer radial sculpture and a more depressed aperture (aperture 1.1-1.2 mm high, at a shell height of 2.1-2.7 mm).

Kaliella scandens and Kaliella doliolum are similar in shape but have a far more regular radial sculpture, consisting of densely placed ribs.

Etymology.

The name refers to the shell surface [rugulosus (L.) = finely wrinkled].