Ditropopsis koperbergi (Zilch, 1955)

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 : 13

Taxon classification Animalia Architaenioglossa Cyclophoridae

Ditropopsis koperbergi (Zilch, 1955) Figure 11

Ditropopsis koperbergi (Zilch) Schilthuizen, 2004: 94. Ditropis koperbergi Zilch, 1955: 193. Type from Indonesia, Kalimantan, Landak.

Examined material from Sabah.

West Coast Province, Kinabalu N.P., Monggis-Tambuyukon trail at 1144 m (leg. T.S. Liew, BOR/MOL 4122). Interior Province. Gunung Trusmadi slopes, Gua Loloposon (leg. J.J. Vermeulen, V 13226). Sandakan Province. Segama valley, North end of limestone ridge on East bank Tabin River (leg. J.J. Vermeulen & M. Schilthuizen, V 14490). Tawau Province. Danum Valley Conservation Area (leg. UMS students, V 9881; leg. H.A. Rutjes, BOR/MOL 312).

Description.

Shell very small, rather thick, somewhat translucent, white to pale corneous. Surface shiny. Spire conical, apex not protruding, not oblique. Sculpture. Radial sculpture: fine growth lines, locally grading into fine, densely placed riblets. Spiral sculpture on the last whorl: 6 rather distinct cords: 1 supraperipheral and 1 peripheral, about equally wide, 1 basal and 3 umbilical; next to these a fine spiral striation on the lower sureface. Sculpture continuing up to the peristome. Aperture. Peristome simple, not expanded, parietal side attached to the penultimate whorl, basal side moderately angular but not drawn out. Dimensions. Height 1.7-2.1 mm; width 1.9-2.2 mm; h/w 0.85-1.00; umbilicus measured over the basal spiral cord 19-27 % of the shell width; number of whorls 4-4 3/4; height aperture 0.7-0.8 mm; width aperture 0.8-0.9 mm.

Habitat in Sabah and distribution.

Primary forest on sandstone and limestone soil, 400-1200 m alt. Sabah: scattered localities. Also in Kalimantan. Endemic to Borneo.

Cross diagnosis.

Ditropopsis koperbergi is characterized by its simple peristome: the aperture is not constricted, and there is no distinctive, rough sculpture close to it.

Elsewhere in Borneo, the conical spire and the angular whorl profile identify the species.