Microcystina physotrochus Vermeulen, Liew & Schilthuizen
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|Microcystina physotrochus Vermeulen, Liew & Schilthuizen|
Taxon classification Animalia Stylommatophora Ariophantidae
Microcystina physotrochus Vermeulen, Liew & Schilthuizen sp. n. Figure 37
Microcystina physotrochus nomen nudum, Clements et al. 2008: 2761-2762; Schilthuizen et al. 2013: online supplementary data.
Holotype. Malaysia, Sabah, Sandakan Province, Kinabatangan Valley , Batu Keruak 2, near Sukau ( RMNH.5003937). View Materials
Examined material from Sabah.
Interior Province. Upper Padas valley, Long Pasia (leg. T.S. Liew & Meckson, BOR/MOL 4354). Gunung Trusmadi slopes: Gua Loloposon (leg. J.J. Vermeulen, V 13243); Gua Dawaras (leg. M. Schilthuizen, V 9873). Pun Batu c. 30 km West of Sepulut (leg. J.J. Vermeulen, V 2643). Sepulut valley, Batu Punggul (leg. J.J. Vermeulen, V 1969); Bukit Tinahas, East end of Batu Punggul limestone (leg. J.J. Vermeulen & M. Schilthuizen, V 7456); Gua Pungiton (leg. J.J. Vermeulen & M. Schilthuizen, V 8082). Sandakan Province. Kinabatangan valley, Batu Mawas (leg. T.S. Liew & M. Schilthuizen, BOR/MOL 1971; leg. M. Schilthuizen, BOR/MOL 1345); Batu Keruak 2 near Sukau (leg. J.J. Vermeulen & M. Schilthuizen, V 12726; leg. M. Salverda & H. van Oosten, BOR/MOL 1347); Hill on Resang river (leg. M. Schilthuizen, BOR/MOL 1346). Segama valley, North end of limestone ridge on East bank Tabin River (leg. J.J. Vermeulen & M. Schilthuizen, V 7500). Tawau Province. Batu Baturong, North slope (leg. J.J. Vermeulen, V 7587). Danum Valley Conservation Area (leg. UMS students, V 9882; leg. M. Schilthuizen, BOR/MOL 1107). Semporna area, Segarong Hills, Batu Tengar, 25 km E.S.E. of Kunak (leg. J.J. Vermeulen & H. Duistermaat, V 2644). Tawau Hills N.P., waterfalls near Headquarters area (leg. J.J. Vermeulen, V 13203). West Coast Province. Kinabalu N.P., plot near Mesilau trail (leg. T.S. Liew et al.; locality 2006.S043, V 14342); Poring (leg. M. Schilthuizen & P. Koomen, BOR/MOL 1114); Sayap-Nunuhon trail between 960 and 1152 m (leg. T.S. Liew, Dominik, J. Lapidin & Jasilin, BOR/MOL 4070, BOR/MOL 4071); Monggis-Tambuyukon trail between 880 and 1144 m (leg. T.S. Liew, BOR/MOL 4072, BOR/MOL 4074, BOR/MOL 4077); Kiau-Spurs route between 2248 and 2624 m (leg. T.S. Liew, J. Lapidin & Safrie, BOR/MOL 4079, BOR/MOL 4085, BOR/MOL 4082); Mesilau trail between 2560 and 2680 m (leg. T.S. Liew, BOR/MOL 4083, BOR/MOL 4084); Serinsim-Numbuyokon trail at 1001 m (leg. T.S. Liew, BOR/MOL 4078); Summit trail between 1616 and 2526 m (leg. T.S. Liew, BOR/MOL 4075, BOR/MOL 4076, BOR/MOL 4080; leg. T.S. Liew & David, BOR/MOL 4081). Crocker Range N.P., Ulu Kimanis (leg. M. Schilthuizen, BOR/MOL 1343); Raflesia Park (leg. M. Schilthuizen, BOR/MOL 1119). Mantanani Group, Pulau Lungisan (leg. M. Schilthuizen, V 9862).
Shell very small, thin, slightly translucent, brown; inflated-lenticular to depressed-ovoid; spire (moderately) elevated (more distinctly elevated in some adults) conical with convex sides or depressed-ovoid, with a rounded apex. Surface glossy. Whorls moderately convex. Protoconch: with or without very fine (only just visible at 40 times magnification), well-spaced, somewhat interrupted, shallow, rather sharply outlined spiral grooves; also with patches of fine, densely placed radial riblets, particularly below the suture. Teleoconch: fine, well-spaced, shallow spiral grooves on the upper and lower surface; sometimes only present on part of the shell, or (almost) entirely absent. Radial sculpture teleoconch: inconspicuous growth lines, next to these rather distinct, well-spaced to densely placed shallow grooves, often at irregular intervals. Umbilicus open, narrow; columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 2.3 mm; width up to 2.9 mm; diameters of the first three whorls 0.5-0.7 mm, 0.9-1.2 mm, 1.3-1.8 mm respectively; number of whorls up to 4 7/8; height aperture up to 1.5 mm; width aperture up to 1.6 mm.
Habitat in Sabah and distribution.
Rainforest, seasonally dry forest, coastal forest, secondary woodland; on limestone and sandstone bedrock, up to 2600 m alt. Sabah: rather common. Usually found in small numbers. Also in Sarawak. Endemic to Borneo.
Generally identified among Sabah Microcystina by the somewhat inflated shell. Relatively flat specimens differ from Microcystina appendiculata because they lack the spur on the columellar side of the peristome.
Elsewhere, the following species have a similar inflated-lenticular or depressed-ovoid shell of comparable size. Sitala infantilis E.A. Smith, 1895, from Palawan, has a corneous shell with a comparatively larger aperture, and a smooth surface, Microcystina seclusa Godwin Austen, 1891, from Sarawak, has the last whorl more narrowly rounded around the periphery. Lamprocystis ambonica Boettger, 1891, from the Moluccas, has a larger aperture. Sitala amussitata E.A. Smith, 1895, from Sarawak, and Lamprocystis subglobosa Von Moellendorff, 1897 (see Van Benthem Jutting 1950: 452), from Java, have the whorls are slightly laterally compressed, resulting in a somewhat shouldered last whorl.
Juveniles and some adults have the basal edge of the peristome more angular than in the illustrated specimen. A small callus (not protruding beyond the rim of the peristome, as in Microcystina appendiculata ) may be present on the columellar peristome in such shells. Shells from Mount Kinabalu tend to be relatively small, with a distinctly elevated spire.
The name refers to the inflated shell shape [phusa (Gr.) = bellows; trokhos (Gr.) = wheel, a word often used for the gastropod spire].
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