Acmella cyrtoglyphe 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 : 3

Taxon classification Animalia Littorinimorpha Assimineidae

Acmella cyrtoglyphe Vermeulen, Liew & Schilthuizen sp. n. Figure 1

Acmella cyrtoglyphe nomen nudum: Clements et al. 2008: 2761-2762.

Holotype. Malaysia, Sabah, Interior Province , Sepulut valley , Gua Sanaron (leg. J.J. Vermeulen & M. Schilthuizen, RMNH.5003948 ).

Examined material from Sabah.

Interior Province. Pinangah valley, Batu Urun (= Bukit Sinobang) (leg. J.J. Vermeulen, V 7977; leg. R. Haegens, V 5635). Pun Batu c. 30 km West of Sepulut (leg. J.J. Vermeulen, V 1271). Sepulut valley, Batu Punggul (leg. J.J. Vermeulen, V 1915); Batu Temurung (leg. J.J. Vermeulen, V 8061); Gua Pungiton (leg. J.J. Vermeulen & M. Schilthuizen, V 7527; leg. M. Schilthuizen, BOR/MOL 609); Gua Sanaron (leg. J.J. Vermeulen & M. Schilthuizen, V 7647; leg. M. Schilthuizen, V 13514, BOR/MOL 601); Gua Sanaron, inside cave (leg. M. Schilthuizen, V 13558). Sandakan Province. Kinabatangan valley, Batu Keruak (leg. M. Salverda, H. van Oosten, BOR/MOL 1775; leg. T.S. Liew & B. Elahan, BOR/MOL 1867); Batu Mawas (leg. T.S. Liew & M. Schilthuizen, BOR/MOL 2013, BOR/MOL 3592); Batu Tomanggong Kecil (leg. T.S. Liew & B. Elahan, BOR/MOL 2045); Batu Pangi (leg. J.J. Vermeulen & M. Schilthuizen, V 9644). Pinangah valley, Batu Melikop (leg. R. Kiew, V 7718). Segama valley, North end of limestone ridge on East bank Tabin River (leg. J.J. Vermeulen & M. Schilthuizen, V 7754; leg. J.J. Vermeulen & M. Schilthuizen, V 7757). Tawau Province. Batu Baturong c. 50 km W.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1844); Batu Baturong, North slope (leg. J.J. Vermeulen, V 7571); Gua Madai c. 40 km S.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1735); Gua Madai c. 40 km S.S.W. of Lahad Datu, N.E.-end (leg. J.J. Vermeulen, V 7677). Segama valley, ‘Kirk’s Cave’ 8 km North of Lahad Datu (leg. J.J. Vermeulen, V 1230). Semporna area, Segarong Hills, Batu Tengar, 25 km E.S.E. Of Kunak (leg. J.J. Vermeulen & H. Duistermaat, V 1811); Bukit Pababola, 25 km E.S.E. of Kunak (leg. J.J. Vermeulen & H. Duistermaat, V 1783).

Description.

Shell minute, thin, somewhat translucent, white. Surface shiny. Spire conical with approx. flat sides, apex obtuse, whorls convex, sometimes slightly shouldered. Sculpture. Radial sculpture predominant: densely placed and regularly spaced, prosocline riblets which are distinctly sinuous around the periphery, and which below the periphery are about as strong as above or weaker, some bifurcating from the periphery downwards. Spiral threads usually present, visible in between the radial riblets, inconspicuous to rather distinct, (rather) densely placed at regular intervals. Aperture approx. obliquely elliptic in outline, with a straight parietal side, transition from parietal to basal side rounded to obtusely angular. Umbilicus open, (rather) wide. Dimensions. Height 1.00-1.50 mm; width 0.85-1.10 mm; h/w 1.10-1.36; number of whorls 4 1/8-5 7/8; height aperture 0.35-0.50 mm; width aperture 0.37-0.50 mm.

Habitat in Sabah and distribution.

Primary and secondary forest on limestone bedrock, at 0-700 m alt. Sabah: Interior Province, South part; East coast: from Kinabatangan River valley and further South. Also in Sarawak, Kalimantan. Endemic to Borneo.

Cross diagnosis.

Shares the prominent, prosocline radial sculpture with Acmella roepstoffiana Godwin Austen & Nevill, 1879, from the Nicobar Islands. Acmella cyrtoglyphe differs by the more convex whorls and the wider umbilicus, which is not at all covered by the peristome.

Remarks.

The material of this species displays variability in two characters but we are not able to divide it into discrete units. The ratio height/width varies, and with it the width of the umbilicus. The spacing of the radial ribs above the periphery also varies; specimens with moderately spaced radial ribs above the periphery have the radial ribs bifurcating more frequently below the periphery. Next to this, the whorls are more depressed in some specimens than in others.

Etymology.

The name refers to the shape of the riblets [kurtos (Gr.) = bent; glupho (Gr.) = to engrave].