Microcystina oswaldbrakeni, 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 oswaldbrakeni sp. nov. Figures 28A , 29A-F

Material examined.

Holotype (SH 1.79 mm, SW 1.99 mm) (MZU.MOL.20.16), Malaysia, Sarawak, Kuching Division , Bukit Sokwang (Site 2), northern site of Gunung Doya, limestone hill along Skio road, 2.05 miles E Bau, 1°23'45.69"N, 110°10'35.04"E, coll. M. E. Marzuki, 22.IV.2017 . Paratypes: 2 ex. (MZU.MOL.20.17),> 10 ex. (ME0002268), same data as the holotype ; 6 ex. (ME0001758), 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, 23.VI.2010 ; 1 ex. (ME0003275), the same locality, coll. M. E. Marzuki, 10.VII.2011 ; 4 ex. (ME0008818), the same locality, coll. M. E. Marzuki, 10.II.2017 ; 1 ex (ME0010295), Gua Tupap , Northern Gunung Batu Complex , Jambusan, 2.51 miles E Bau, Kuching Division, 1°24'21.25"N, 110°11'21.70"E, coll. M. E. Marzuki, 26.XII.2018 ;> 10 ex. (ME0001751), Gunung Doya , limestone hill near Sungai Sebuyoh, 3.4 miles SE Bau, 1°22'57.24"N, 110°11'39.42"E, coll. M. E. Marzuki, 10.VII.2011 ; 3 ex (ME0007194), Fairy Caves (Site 1), south part of Gunung Kapor, 4 miles SW Bau, 1°22'53.76"N, 110°7'4.34"E, coll. M. E. Marzuki, 17.IX.2016 ; 1 ex. (ME0010478), the same locality, coll. M. E. Marzuki, 10.II.2017 ; 1 ex. (ME0011473), Fairy Caves (Site 2), south part of Gunung Kapor, 4 miles SW Bau, 1°22'56.09"N, 110°6'58.82"E, coll. M. E. Marzuki, 8.IV.2017 ; 2 ex. (ME0008012), Gunung Sebayat , limestone hill near Bengoh resettlement scheme, along Jambusan-Semadang road, 10 miles SE Bau, 1°18'24.54"N, 110°15'21.80"E, coll. M. E. Marzuki, 13.IX.2016 ; 10 ex. (ME0001796), Gunung Suka , Limestone outcrop near Kampung Picsing, Tebakang-Tebedu road, 8.45 miles SW Serian, 1°8'5.08"N, 110°26'53.30"E, coll. M. E. Marzuki, 20.VI.2010 .

Differential diagnosis.

It differs from Microcystina seclusa Godwin-Austen, 1891 in having a smaller shell with a silky surface that is covered by well-spaced faint spiral grooves and a closed umbilicus. This species also similar to Microcystina arabii sp. nov., see Remarks under that species.

Description.

Shell very small, thin, translucent, brown; conical-ovoid with convex sides, spire elevated, apex rounded. Surface with a glossy lustre. Whorls convex, rounded or slightly angular. Number of whorls < 5½. Protoconch with very fine, moderately spaced spiral striation consisting of rows of minute spiral grooves crossed by inconspicuous radial riblets towards the teleoconch. Teleoconch: spiral sculpture obsolete or with densely spaced, continuous, inconspicuous, narrow spiral grooves above the periphery but rather well-spaced below the periphery. Radial sculpture inconspicuous, oblique, widely but irregularly spaced, growth lines. Aperture lunulate. Peristome simple; somewhat reflected on columellar side, not thickened nor reflected on basal and palatal side. Umbilicus open, narrow, partly, or almost closed by reflected peristome; umbilical region is moderately concave. Dimensions: shell height <1.79 mm; shell width <1.99 mm; diameters of the first three whorls 0.42 mm, 0.74 mm, and 1.05 mm, respectively; aperture height <0.73 mm; aperture width <1.05 mm.

Geographic distribution and habitat.

It is known from the Bau and Serian-Padawan limestone hill clusters. Only dry shells were found during the surveys.

Etymology.

The specific epithet honours Mr. Oswald Braken Tisen, Deputy Chief Executive Officer of Sarawak Forestry Corporation, who has contributed significantly to the conservation of wildlife in Sarawak.

Figures

Figure 28. A Microcystina oswaldbrakeni, sp. nov., MZU. MOL. 20.17 Paratype Gunung Batu B Microcystina paripari, sp. nov., ME 1746 Paratype Gunung Batu C Microcystina physotrochus Vermeulen, Liew & Schilthuizen, 2015 ME 9072 Gunung Kapor D Microcystina seclusa Godwin-Austen, 1891 ME 8153 Gunung Kapor.

Figure 29. Microcystina oswaldbrakeni, sp. nov. A-F MZU. MOL. 20.16 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.