Alycaeus liratulus Preston, 1907

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 : 34-36

Alycaeus liratulus Preston, 1907 Figures 7C, 23, 31B

Alycaeus (Pincerna) liratula Preston, 1907: 206; Robertson et al. 1987: 4; Tarruella and Domènech 2011: 72; Mienis 2014: 37.

Alycaeus (Alycaeus) liratulus : Laidlaw 1928: 35; Benthem Jutting 1959: 77; Maassen 2001: 22; Clements et al. 2008: 2760.

Alycaeus liratulus : Marwoto 2016: 17.

Pincerna liratula : Páll-Gergely 2017: 213-219, figure 1C.

Type locality.

Kelantan.

Type material.

Syntypes. Ke-lan-tan (=Kelantan): ANSP 99391/1 (Seen), NHMUK 1907.5.20.191-192/2 (1 specimen seen), HUJ 22445 (Not seen).

Other examined materials.

Mykarst-186 Gua Madu, Kelantan: BOR/MOL 6826/2. KTN 136 Gua Musang, Kelantan: ZRC 1975.2.22.4-7/4. KTN 176 Batu Lesong, Kelantan: BOR/MOL 6831/1. KTN 149 unnamed hill, Kelantan: BOR/MOL 6832/1, BOR/MOL 8334/3. Mykarst-168, Kelantan: BOR/MOL 8411/2.

Description.

Protoconch. Smooth.

Shell shape and size.

Globose. Shell height: 5.62-6.70 mm. Shell width: 5.195-6.08 mm.

Spire. Spire height: 1.42-2.01 mm. Spire width: 2.30-2.83 mm. Number of whorls: up to 4 ⅛. Spire shape: oblong conical. Whorl periphery rounded. Umbilicus open.

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

Breathing tube. Length: 1.13-1.25 mm.

Aperture and peristome. Aperture circular, moderately expanded. Aperture height: 2.78-3.16 mm. Aperture width: 2.88-3.43 mm. Peristome double, thickened, slightly notched at suture. No interspace. Peristome orientation 9-20° oblique with respect to the coiling axis.

Spiral lines. Distinct. Regularly spaced. Approximately 11-14 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs pronounced, evenly spaced. Approximately 6-7 ribs per 1 mm.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced, evenly spaced. Approximately 9-12 ribs per 1 mm.

Radial ribs running posterior of breathing tube. Radial ribs absent immediately posterior of constriction, becoming distinct and unevenly spaced at the middle and then absent again prior to aperture.

Operculum. Concave, rounded. Exterior covered by calcareous layer. Exterior nucleus with calcareous, cup-like projection. Interior covered by proteinaceous layer, smooth, mamillated.

Shell colour. Off white, apical whorls occasionally pinkish white.

Living animal. Body maroon. Head maroon. Tentacles red or brown tipped.

Habitat and ecology.

Lives on shrubs close to the ground. In forested areas of limestone hills.

Distribution.

Restricted to central and southern Kelantan. Elsewhere, isolated records in northern Sumatra, Indonesia ( Benthem Jutting 1959, Marwoto 2016) need to be verified.

Differential diagnosis.

Alycaeus liratulus is most similar to Alycaeus thieroti in shell shape but differs in having a larger shell (larger by about 1 mm in shell height, 0.8 mm in shell width), wider-spaced radial ribs and spiral lines, longer breathing tube (longer by 0.65 mm) and flat operculum with cup-shaped calcareous extension at the nucleus exterior.

Discussion.

Confusion between A. liratulus and A. thieroti due to similarity in shell shape and poor original descriptions have led to many misidentifications in the past (see Discussion in Alycaeus thieroti ). Isolated records of A. liratulus from northern Sumatra ( Benthem Jutting 1959, Marwoto 2016) have to be re-examined. Laidlaw (1928) considers A. liratulus as closely related to the A. globosus of Borneo, an opinion we concur based on its globose shell. However, A. globosus differs from A. liratulus in the arrangement and density of radial ribs, short breathing tube and absence of a cup-shaped projection at the operculum exterior.

Supraspecific classification was attempted for A. liratulus by Preston (1907), who created a new subgenus Pincerna based on the sole diagnostic character of the cup-shaped protrusion on the operculum exterior of A. liratulus . However, the operculum structure is an unsuitable diagnostic character because analogous structures have also been found in Alycaeus kukenthali Sarasin & Sarasin, 1899 and Alycaeus ochraceus Godwin-Austen, 1893, two species unrelated in shell shape to A. liratulus ( Sarasin and Sarasin 1899, Laidlaw 1928, Páll-Gergely 2017). Note that we maintained Pincerna as a subgenus of Alycaeus although Pincerna was recently elevated to genus level ( Páll-Gergely 2017). See Remarks section under genus Alycaeus for discussion.