Alycaeus thieroti Morgan, 1885b

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 : 44-47

Alycaeus thieroti Morgan, 1885b Figures 7D, 29, 31C

Alycaeus thieroti Morgan, 1885b: 403-404, plate 10; Venmans 1956: 82, figure 3; Benthem Jutting 1960a: 13; Sykes 1903: 197; Chan 1997: 37; Maassen 2001: 23; Clements et al. 2008: 2760; Tarruella and Domènech 2011: 73; Foon et al. 2017: 13, figure 5A.

Alycaeus (Orthalycaeus) thieroti : Möllendorff 1891: 342; Kobelt and Möllendorff 1897: 151.

Alycaeus (Alycaeus) thieroti : Kobelt 1902: 352; Laidlaw 1928: 35; Laidlaw 1932: 36.

Alycaeus liratulus : Liew 2010: 101. [not Alycaeus liratulus (Preston, 1907)]

Pincerna thieroti : Páll-Gergely 2017: 213-214.

Type locality.

PRK 18 Gunung Lanno, Perak (4°31'31"N, 101°08'48"E).

Type material.

Syntype. Gunong Lano (= PRK 18 Gunung Lanno), Perak: MNHN IM-2000-31799/5 (1 specimen seen).

Other examined materials.

Endau-Kluang, Johor: BOR/MOL 6466/1, BOR/MOL 6467/1. KTN 01 Gunung Reng, Kelantan: BOR/MOL 6835/1, BOR/MOL 8335/6. KTN 95 Gua Panjang, Kelantan: BOR/MOL 12962/5. Lojing, Kelantan: BOR/MOL 6528/2. PHG 01 Kota Gelanggi, Pahang: BOR/MOL 6886/2, BOR/MOL 6636/1. PHG 02 Gunung Senyum, Pahang: BOR/MOL 12961/4. PHG 03 Gunung Jebak Puyuh, Pahang: BOR/MOL 6885/3. PHG 05 Bukit Cintamanis, Pahang: BOR/MOL 6633/1. PHG 75 Bukit Tenggek, Pahang: ZRC 1975.2.22.8-11/2. PHG 77 Bukit Mengapur, Pahang: BOR/MOL 6889/1. Unnamed limestone hill north of Jalan Lipis-Gua Musang Lama, Felda Chegar Perah I and II, Pahang: BOR/MOL 6815/1. Gunung Tangkup, Kenong Rimba, Pahang: BOR/MOL 6237/1. Gunung Kesong, Kenong Rimba, Pahang: BOR/MOL 6253/2. PRK 55 Gunung Pondok, Perak: BOR/MOL 8410/1. PRK 23 Gunung Rapat, Perak: BOR/MOL 10056/4, BOR/MOL 10258/2. PRK 62 Gunong Dayak, Perak: ZRC 1975.2.22.1/1. Mykarst-025, Perak: BOR/MOL 9415/1, BOR/MOL 12422/1. Lenggong, Perak: ZRC 1975.2.22.2-3/2. SGR 02 Bukit Takun, Selangor: ZRC 1997.27/5.

Description.

Protoconch. Smooth.

Shell shape and size.

Globose. Shell height: 4.55-5.68 mm. Shell width: 4.36-5.34 mm.

Spire. Spire height: 1.06-1.58 mm. Spire width: 1.73-2.30 mm. Number of whorls: up to 4. Spire shape: oblong conical. Whorl periphery rounded. Umbilicus open or partially closed.

Whorl constriction. At about 3 ⅝ whorls posterior of protoconch.

Breathing tube. Length: 0.40-0.53 mm.

Aperture and peristome. Aperture circular, moderately expanded. Aperture height: 2.28-2.76 mm. Aperture width: 2.42-2.98 mm. Peristome double, thickened, notched at suture. No interspace. Peristome orientation 15-18° oblique with respect to the coiling axis.

Spiral lines. Distinct. Regularly spaced. 20-37 lines per 1 mm.

Radial ribs running anterior of breathing tube. Radial ribs pronounced, evenly spaced. Approximately 8-15 ribs per 1 mm.

Radial ribs running perpendicular to breathing tube. Radial ribs pronounced, evenly spaced. Approximately 9-21 ribs per 1 mm.

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

Operculum. Almost flat. Exterior covered by calcareous layer. Exterior has calcareous ridges radiating outwards of the nucleus. Interior covered by proteinaceous layer, smooth.

Shell colour. Variable - red, yellow or white.

Living animal. Body cream-white or maroon. Head pink. Tentacles red or brown tipped.

Habitat and ecology.

Lives in crevices on wet limestone boulders and shrubs close to the ground. In thickly forested areas. Lives in both limestone and non-limestone areas.

Distribution.

Widespread in Perak, Selangor, Kelantan and Pahang.

Differential diagnosis.

Alycaeus thieroti is most similar to Alycaeus liratulus in shell shape but differs in having a smaller and more elongated shell (smaller by about 1 mm in shell height, 0.8 mm in shell width), narrowly-spaced radial ribs and spiral lines, shorter breathing tube (shorter by 0.65 mm) and flat operculum with calcareous ridges radiating out from the exterior nucleus.

Discussion.

Morgan (1885b) first described A. thieroti with simple shell characters and an erroneous description of the operculum as smooth and proteinaceous. Möllendorff (1891) subsequently redescribed the species with additional shell characters but did not point out the error. The operculum is a critical diagnostic feature that clearly distinguishes A. thieroti from A. liratulus . Thus, this uncorrected error has led to the misidentification of A. thieroti as A. liratulus and vice versa (e.g. Liew 2010, ZRC collection lots). Alycaeus thieroti was known from Perak, Selangor and Kelantan prior to this study ( Morgan 1885b, Möllendorff 1891, Sykes 1903, Laidlaw 1928, Laidlaw 1932, Benthem Jutting 1960a, Venmans 1956). Alycaeus thieroti in Pahang and Johor are new records. Venmans (1956) examined the radular and jaw features of A. thieroti , which is distinct from A. selangoriensis sp. n. but similar to A. conformis in teeth arrangement. 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.