Alycaeus carinata Maassen, 2006

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 : 13-15

Alycaeus carinata Maassen, 2006 Figures 11, 31Q

Alycaeus carinata Maassen, 2006: 137-138, figures 10-13; Tarruella and Domènech 2011: 72.

Type locality.

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

Type material.

Holotype. PHG 74 Bukit Sagu, Pahang: RMNH 104428 (Not seen). Paratypes. PHG 74 Bukit Sagu, Pahang: RMNH 104427/2 (1 specimen seen), HW /58 (Not seen), ANSP /2 (Not seen), HW /200 (Not seen). PHG 75 Bukit Tenggek, Pahang: RMNH 104426/2 (Not seen), HW /37 (Not seen).

Description.

Protoconch. Smooth.

Shell shape. Almost flat, conical. Shell height: 2.2-3.0 mm. Shell width: 4.0-4.6 mm. Shell measurements derived from Maassen (2006) and re-examination of one paratype (RMNH 104427).

Spire. Spire height: 3.0 mm. Spire width: 4.5 mm. Number of whorls: up to 4. Spire shape: oblong conical. Whorl periphery strongly keeled except posterior of the constriction, where it becomes rounded. Umbilicus open.

Whorl constriction. At about 3 ¾ whorls posterior of protoconch.

Breathing tube. Length: 0.3 mm.

Aperture and peristome. Aperture circular, moderately expanded. Aperture height: 2.2 mm. Aperture width: 2.0 mm. Peristome double, not thickened, winged at suture. Interspace narrow. Peristome orientation is 30-55° oblique with respect to the coiling axis.

Spiral lines. Indistinct. Regularly spaced. Approximately 25 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs indistinct to absent, only unevenly spaced radial growth lines present.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced, evenly spaced. Approximately 13 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs indistinct to absent, only unevenly spaced radial growth lines present.

Operculum. Concave, rounded. Exterior and interior composition and sculpture not examined. Maassen (2006) considered the operculum entirely proteinaceous.

Shell colour. Whorls yellow to brown. Peristome white.

Living animal. Unknown.

Habitat and ecology.

Lives on limestone walls in a large, collapsed cave ( Maassen 2006). Probably prefers very moist environments only ( Maassen 2006).

Distribution range.

Restricted to Bukit Sagu and Bukit Tenggek, Pahang.

Differential diagnosis.

Alycaeus carinata is distinguished from all other Peninsular Malaysian Alycaeus species by its strongly keeled periphery, relatively low spire, very expanded ultimate whorls and very oblique peristome orientation with respect to the coiling axis ( Maassen 2006).

Discussion.

Interestingly, no A. carinata was found during the 1950s University of Malaya, Singapore expedition to the type locality although congeners Alycaeus charasensis sp. n. and Alycaeus expansus sp. n. were obtained (ZRC collection lots). This suggests A. carinata may be restricted to upper sections of limestone hills that became accessible only during quarrying in the 1990s. However, viable habitats at Bukit Sagu and Bukit Tenggek are now very likely lost to quarrying ( Schilthuizen and Clements 2008, Liew et al. 2014).