Geotrochus oedobasis 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 : 103-104

Taxon classification Animalia Stylommatophora Trochomorphidae

Geotrochus oedobasis Vermeulen, Liew & Schilthuizen sp. n. Figure 85

Holotype. Malaysia, Sabah, West Coast Province , Kinabalu N.P. , Headquarters area (leg. M. Schilthuizen, RMNH.5003929 ).

Examined material from Sabah.

Interior Province. Crocker Range, Gn. Emas (leg. M. Schilthuizen, BOR/MOL 909); Gunung Trusmadi slopes, Gua Loloposon (leg. J.J. Vermeulen, V 13258; leg. M. Schilthuizen & P. Koomen, BOR/MOL 911); Gua Dawaras (leg. M. Schilthuizen, V 13522; leg. M. Schilthuizen & M. Suleiman, BOR/MOL 2418, BOR/MOL 2419). West Coast Province. Kinabalu N.P., Headquarters area (leg. J.J. Vermeulen, V 1191); Summit trail between 1350 and 1800 m (leg. M. Schilthuizen, BOR/MOL 908; leg. T.S. Liew, BOR/MOL 4400); Mesilau trail between 2040 and 2112 m (leg. T.S. Liew & J. Lapidin, BOR/MOL 4399, BOR/MOL 4404, BOR/MOL 4407; leg. T.S. Liew, BOR/MOL 4406, BOR/MOL 4408).

Description.

Shell medium-sized, rather thin, opaque, uniformly somewhat pale brown, periphery pale brown; shell low-conical with approx. flat or slightly concave sides, apex not or hardly protruding. Surface with a silky luster above the periphery, shiny below. Whorls: apical whirls slightly convex others approx. flat; suture somewhat impressed in the inner whorls, not so in the outer, coinciding with the periphery; last whorl acutely angular, (moderately) compressed at the periphery, moderately to distinctly convex below the periphery. Protoconch 2-2 1/8 whorls, smooth. Teleoconch. Radial sculpture: above and below the periphery scattered inconspicuous growth lines, locally grading into inconspicuous riblets; next to this a very fine (just visible at 40 times magnification) radial wrinkling of the shell surface is locally present. Spiral sculpture: last whorl with a sharp, slightly pinched peripheral ridge; start of fifth whorl with 19-23 somewhat spaced, low and thin spiral threads, the 2-5 threads close to the periphery slightly more distinct, the others inconspicuous; no spiral sculpture below the periphery. Umbilicus closed. Peristome thickened and reflexed, basal edge more or less evenly rounded from the columellar side to the periphery. Dimensions: Height 6.0-8.5 mm; width 13.5-18.0 mm; h/w 0.39-0.45; peripheral keel of the last whorl at 0.33-0.40 of the shell height, measured from the apex; diameters of the first 4 whorls 1.3-1.4 mm, 2.2-2.3 mm, 3.7-4.0 mm, 5.9-6.4 mm respectively; number of whorls 6-7 1/8, height aperture 3.5-5.2 mm; width aperture 7.0-10.0 mm. Shell medium-sized, thin, about opaque, uniformly pale yellowish brown.

Habitat in Sabah and distribution.

Forest on sandstone or limestone soil, also found in grassy roadside with forest nearby, alt. 900-2200 m. Sabah: Mount Kinabalu, Mount Trusmadi. Endemic to Sabah.

Cross diagnosis.

See under Geotrochus labuanensis . Differs from Geotrochus kinabaluensis by the evenly rounded basal peristome. Relative to the shell height, the peripheral keel is positioned closer to the apex of the shell. It makes the lower side of the shell appear more convex, and the upper side flatter than in Geotrochus kinabaluensis .

Etymology.

The name refers to the convex lower side of the shell [oidos (Gr.) = swelling; basis (Gr.) = base].