Alycaeus expansus, Foon, Junn Kitt & Liew, Thor-Seng, 2017

Foon, Junn Kitt & Liew, Thor-Seng, 2017, A review of the land snail genus Alycaeus (Gastropoda, Alycaeidae) in Peninsular Malaysia, ZooKeys 692, pp. 1-81 : 22-23

Alycaeus expansus sp. n. Figures 7N, 16, 31I

Type locality.

PHG 74 Bukit Sagu, Pahang (3°58'54"N, 103°08'39"E).

Type material.

Holotype. PHG 74 Bukit Sagu, Pahang: BOR/MOL 12983. Paratypes. PHG 74 Bukit Sagu, Pahang: BOR/MOL 269/2, BOR/MOL 6358/4. PHG 75 Bukit Tenggek, Pahang: BOR/MOL 273/2.

Other examined materials.

PHG 72 Bukit Panching, Pahang: BOR/MOL 247/1, ZRC 1975.2.24.352-355/3, ANSP 439118/8. PHG 73 Bukit Charas, Pahang: BOR/MOL 245/1, BOR/MOL 6367/1, BOR/MOL 6890/1, BOR/MOL 8400/9, BOR/MOL 12984/1, ZRC 1975.2.21.956-1015/63, ZRC 1975.2.21.876-955/81, ZRC 1975.2.21.435-488/53, ZRC 1975.2.21.732-831/101. PHG 74 Bukit Sagu, Pahang: ZRC 1975.2.21.532-556/26. PHG 75 Bukit Tenggek, Pahang: ZRC 1975.2.24.723-725/2, ZRC 1975.2.21.489-531/44.

Etymology.

Latin, meaning expanded. In reference to the very expanded peristome and globose whorls.

Description.

Protoconch. Smooth.

Shell shape. Conical. Shell height: 4.11-5.88 mm. Shell width: 3.87-5.96 mm.

Spire. Spire height: 1.33-1.85 mm. Spire width: 1.88-2.57 mm. Number of whorls: up to 4 ½. Spire shape: oblong conical. Whorl periphery rounded. Umbilicus open.

Whorl constriction. At about 4 ¼ whorls posterior of protoconch.

Breathing tube. Length: 0.44-0.62 mm.

Aperture and peristome. Aperture very expanded, ocassionally forming wing-like extensions at columellar and upper palatal sections. Wing-like extension at columellar section of the aperture is angular. Aperture height: 1.81-3.44 mm. Aperture width: 1.78-3.13 mm. Peristome double, not thickened, notched at suture. Peristome orientation 27-32° oblique with respect to the coiling axis.

Spiral lines. Indistinct. Regularly spaced. Approximately 18-40 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs indistinct, evenly spaced. Approximately 6-15 ribs per 1 mm.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced and thicker than those anterior of breathing tube, evenly spaced. Approximately 11-17 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs indistinct, unevenly spaced to absent.

Operculum. Concave, conical. Exterior covered with thick calcareous layer, surface finely granulated. Interior covered with proteinaceous coating, smooth, mamillated.

Shell colour. Whorls yellow. Peristome white.

Living animal. Body cream-white. Head pink. Tentacles cream-white, tips pink.

Habitat and ecology.

Lives on wet rock surfaces and crevices covered with mosses at higher areas and wang of limestone hills. In shaded forests.

Distribution range.

Restricted to the Kuantan Hills of eastern Pahang (comprises of Bukit Tenggek, Bukit Sagu, Bukit Charas and Bukit Panching).

Differential diagnosis.

Alycaeus expansus sp. n. is distinguished from all other Peninsular Malaysian Alycaeus by its very obtuse ultimate whorl, very expanded peristome with wing-like extensions at columellar and upper palatal sections, thick operculum and animal colouration.

Discussion.

Prior to this study, shells of A. expansus sp. n. from Bukit Charas and Bukit Panching were labelled as A. kelantanensis (BOR/MOL and ZRC collection lots). Shells of A. expansus sp. n. is consistent in its diagnostic obtuse ultimate whorl and very expanded peristome across its range but varies in shell size and spire height for each hill population. Shells from Bukit Sagu and Bukit Tenggek (the northern two of the Kuantan Hills) tend to be larger with ultimate whorl always obtused and spire low. Shells from Bukit Charas and Bukit Panching (the southern two of the Kuantan Hills) tend to be slightly smaller and more variable in ultimate whorl shape (obtuse to normal) and spire height (tall to low). It is possible that A. expansus sp. n. may contain two cryptic species pending availability of molecular data for investigation. Unfortunately, populations on Bukit Panching, Bukit Tenggek and Bukit Sagu are now likely lost to limestone quarrying (see Discussion in A. carinata ).