Microcystina callifera 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 : 32-33

Taxon classification Animalia Stylommatophora Ariophantidae

Microcystina callifera Vermeulen, Liew & Schilthuizen sp. n. Figure 25, 29

Microcystina callifera nomen nudum, Clements et al. 2008: 2761-2762; Schilthuizen et al. 2013: online supplementary data.

Holotype. Malaysia, Sabah, Mantanani Group , Pulau Lungisan ( RMNH.5003934 ).

Examined material from Sabah.

Kudat Province. Banggi Island, South end, Karakit Hill (leg. J.J. Vermeulen & M. Schilthuizen, V 9499). West Coast Province. Mantanani Group, Pulau Lungisan (leg. M. Schilthuizen, V 9861; leg. M. Schilthuizen & T.H. Liew, BOR/MOL 3746); Pulau Mantanani Besar (leg. M. Schilthuizen, V 9849; leg. T.H. Liew, BOR/MOL 3715); Pulau Mantanani Kecil (leg. M. Schilthuizen, V 9856; leg. T.H. Liew, BOR/MOL 3732).

Description.

Shell very small, (rather) thin, almost opaque or slightly translucent, white, lenticular; spire almost flat to moderately elevated. Surface with a silky luster. Whorls slightly convex. Protoconch with inconspicuous, widely spaced, continuous, shallow, vaguely outlined spiral grooves, as well as with fine, widely spaced, shallow radial riblets towards the teleoconch. Teleoconch: upper surface with very fine, widely spaced, continuous, moderately raised, sharply outlined spiral threads; lower surface with equally fine, widely spaced, shallow grooves. This sculpture is sometimes rather distinct, sometimes inconspicuous and patchy. Radial sculpture teleoconch: growth lines inconspicuous, in some specimens locally grading into irregularly and rather densely placed to widely spaced, shallow grooves. Umbilicus closed by a callous extension of the columellar corner of the peristome, the same callus also narrowing the aperture on the columellar side. Dimensions: Height up to 1.5 mm; width up to 2.5 mm; diameters of the first three whorls 0.5-0.6 mm, 0.9-1.0 mm, 1.2-1.4 mm respectively; number of whorls up to 4 1/2; height aperture up to 1.0 mm; width aperture up to 1.4 mm.

Habitat in Sabah and distribution.

Coastal woodland on limestone soil. Sabah: Islands: Mantanani Group and Banggi Island. Endemic to Sabah.

Cross diagnosis.

Uniquely identified within Microcystina by the callus on the columellar side of the aperture. Substantial series of shells all have this callus, rendering the possibility of malformation unlikely. The spiral sculpture is usually more distinct, and more widely spaced than in Microcystina striatula .

Etymology.

The name refers to the callus in the aperture.