Microcystina atoni, Marzuki & Liew & Mohd-Azlan, 2021

Marzuki, Mohammad Effendi bin, Liew, Thor-Seng & Mohd-Azlan, Jayasilan, 2021, Land snails and slugs of Bau limestone hills, Sarawak (Malaysia, Borneo), with the descriptions of 13 new species, ZooKeys 1035, pp. 1-113 : 1

Microcystina atoni sp. nov. Figures 23B , 25A-F

Material examined.

Holotype (SH 1.38 mm, SW 2.46 mm) (MZU.MOL.20.10), Malaysia, Sarawak, Kuching Division , Gunung Batu , limestone outcrop along Skio road, Jambusan, 2.4 miles E Bau, 1°23'50.65"N, 110°11'19.99"E, coll. M. E. Marzuki, 10.VII.2011 . Paratypes: 1 ex. (MZU.MOL.20.11), 1 ex. (ME0009903), same data as the holotype .

Differential diagnosis.

It is similar to Microcystina chionodiscus Vermeulen, 1996 and Microcystina striatula Vermeulen, Liew & Schilthuizen, 2015 in terms of the shell shape, but does not have the spiral striations on the protoconch and teleoconch. It is also different from Microcystina microrhynchus Vermeulen, Liew & Schilthuizen, 2015 and Microcystina kilat sp. nov. in lacking shell grooves and radial sculptures, and with an open but narrow umbilicus.

Description.

Shell very small, thin, translucent, white, lenticular, spire almost flat or slightly elevated. Surface with a slightly silky lustre. Whorls slightly convex. Number of whorls <4. Protoconch dull, without spiral and radial threads. Teleoconch with spiral sculpture absent. Radial sculpture teleoconch: growth lines very fine, inconspicuous. Aperture lunulate. Peristome simple; somewhat thickened and reflected on columellar side, not thickened nor reflected on basal and palatal side. Umbilicus open, narrow; columellar wall very thick; umbilical region concave. Dimensions: shell height <1.38 mm; shell width <2.46 mm; diameters of the first three whorls 0.50 mm, 1.00 mm, and 1.58 mm, respectively; aperture height <1.00 mm; aperture width <1.25 mm.

Geographic distribution and habitat.

It is known from the Bau limestone hill clusters only. Only dry shells were found during the surveys.

Etymology.

The specific epithet honours Mr. Zolkipli Mohamad Aton, Chief Executive Officer of Sarawak Forestry Corporation, Controller of Wildlife and Controller of National Parks and Nature Reserves, who has contributed significantly to the conservation of wildlife in Sarawak.

Figures

Figure 23. A Microcystina arabii, sp. nov., MZU. MOL. 20.06 Holotype Gunung Batu B Microcystina atoni, sp. nov., MZU. MOL. 20.11 Paratype Gunung Batu C Microcystina kilat, sp. nov., MZU. MOL. 20.19 Paratype Gunung Batu D Microcystina lirata, sp. nov., MZU. MOL. 20.15 paratype Gunung Kapor.

Figure 25. Microcystina atoni sp. nov. A-F MZU. MOL. 20.10 Holotype A apertural view B apical view C basal view D enlargement of the apical side showing the apex E enlargement of the teleoconch showing the shell sculpture F enlargement of the basal side of the shell.