Chamalycaeus krabiensis Páll-Gergely & A. Reischütz, 2021

Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Reischütz, Alexander & Auffenberg, Kurt, 2021, Nineteen new species of Alycaeidae from Myanmar and Thailand (Gastropoda: Caenogastropoda: Cyclophoroidea), Zootaxa 4973 (1), pp. 1-61 : 17

Chamalycaeus krabiensis Páll-Gergely & A. Reischütz n. sp.

Fig. 11

Material examined. Holotype: Thailand, Krabi Province, Phi-Phi Islands, Phi Phi Don Island, climbing rock at W end of beach in Ton Sai Bay , 7°44.011’N, 98°45.936’E, ca. 70 m a.s.l. (locality code: Th22), Mar. 2010, A. Reischütz leg., at base of limestone rocks in the forest, NHMW 113487 (D: 3.61 mm, H: 2.62 mm) . Paratypes: 1 shell, same data as holotype; 1 shell, Thailand, Krabi Province, Phi-Phi Islands, Phi Phi Don Island, ascent to climbing rock at W end of beach in Ton Sai Bay , 7°44.049’N, 98°45.966’E, ca. 20 m a.s.l. (locality code: Th 21), Mar. 2010, A. Reischütz leg., at base of limestone rocks in forest, NHMW 113488 (photographed paratype: Fig. 11B, D : 3.73 mm, H: 2.37 mm) ; 9 shells, same data as preceding, RE ; 2 shells, same data as preceding, CUMZ 5269 ; 7 shells, Thailand, Krabi Province, Phi-Phi Islands, Phi Phi Don Island, limestone rocks at Monkey Beach , 7°43.386’N, 98°46.135’E, ca. 10 m a.s.l. (locality code: Th 23), Mar. 2010, A. Reischütz leg., RE . Other material: 4 juvenile / broken shells, Thailand, Krabi Province, Phi-Phi Islands, Phi Phi Don Island, ascent to climbing rock at W end of beach in Ton Sai Bay , 7°44.049’N, 98°45.966’E, ca. 20 m a.s.l. (locality code: Th 21), Mar. 2010, A. Reischütz leg., at base of limestone rocks in forest, RE ; 5 juvenile /broken shells, Thailand, Krabi Province, Phi-Phi Islands, Phi Phi Don Island, limestone rocks at Monkey Beach , 7°43.386’N, 98°46.135’E, ca. 10 m a.s.l. (locality code: Th 23), Mar. 2010, A. Reischütz leg., RE ; 7 shells, 1.5 km SE of Ao Luek Tai , 8°22.386’N, 98°44.130’E, 40–45 m a.s.l., 16–19 Mar. 2020, S. Aiken leg., SA ; 4 shells (one photographed here: Fig. 11C ), 1.7 km SE of Ao Luek Tai , 8°22.020’N, 98°44.004’E, 25 m a.s.l., 19 Mar. 2020, S. Aiken leg., in dry debris on rock, at base of limestone cliff, SA .

Etymology. This new species is named for the Thai province in which it occurs.

Diagnosis. A medium-sized Chamalycaeus species with R2 and R3 of almost a quarter whorl each, blunt, elongated swelling on R3, protruding inner peristome, and strongly expanded outer peristome.

Description. Shell off-white to light grey; shell outline slightly oval in dorsal view; spire elevated, conical; body whorl rounded or parabolic; protoconch somewhat elevated, finely granular, rather glossy, spiral striae lacking, 1.5 whorls; R1 of 1.75–2.5 whorls, with strong, narrow, elevated, regularly arranged ribs, spaces between ribs relatively wide, fine spiral striation between ribs; boundary between R1 and R2 distinct due to change in rib density; R2 ribs more elevated than those of R1, narrow, lamella-like; ca. 26–28 ribs present; R2 and R3 of comparable lengths, covering approximately a half whorl or slightly less; boundary between R2 and R3 distinct due to rather deep constriction and change in sculpture; R3 with elongated, convex, central swelling, posterior portion almost smooth, anterior bears ribs of similar density as on R1; aperture strongly oblique to shell axis, rounded, with a very small upper (parieto-palatal) incision; boundary between inner and outer peristomes conspicuous, inner peristome strongly protruding (extreme in some specimens) and slightly expanded; outer peristome slim, strongly expanded except in umbilical region; umbilicus narrow, ca. one fourth of shell width.

Measurements. D: 3.41–3.81 mm, H: 2.34–2.62 mm (type samples).

Operculum. Unknown.

Differential diagnosis. Chamalycaeus reinhardti ( Mörch, 1872) (examined material: Great Nicobar, coll. Godwin-Austen, NHMUK 1903.7.1.2711, 1 shell) and Chamalycaeus reinhardti sabangensis ( Rensch, 1933) (examined material: Sumatra: Wald b. Sabang, Pulu Weh., exp. Rensch, 1927, SMF 6241, 1 paratype) both have a narrower swelling on R3 and a more elevated spire.

Distribution. This species is known from the Phi-Phi Islands and the vicinity of Ao Luek Tai town, Krabi Province, Thailand ( Fig. 3 ).

Remarks. The shells from the two sites near Ao Luek Tai are slightly smaller (D: 2.8–3.3 mm), more depressed and conical from above, have overall denser ribs, lower R3 swelling, and the outer peristome is expanded in a smaller portion of the lip. However, although these differences occur, we consider them conspecific with those from Phi-Phi Islands due to the overall similar sculpture and proportions of shell regions.

Figures

FIGURE 3. Distribution of alycaeid species in southern Thailand. Filled triangle: Dicharax ovatus Páll-Gergely & Auffenberg, n. sp., inverted filled triangle: Dicharax subroseus Páll-Gergely, n. sp., inverted empty triangles: Chamalycaeus irmatallus Páll-Gergely, n. sp., empty circles: C. krabiensis Páll-Gergely & A. Reischütz, n. sp., filled circle: Chamalycaeus serratus Páll-Gergely & Auffenberg, n. sp., empty triangles: Chamalycaeus hirpex Páll-Gergely & A. Reischütz, n. sp., filled square: Chamalycaeus buaboke Páll-Gergely & A. Reischütz, n. sp.

FIGURE 11. Chamalycaeus krabiensis Páll-Gergely & A. Reischütz, n. sp. A: holotype (site Th22, NHMW 113487); B: paratype (site Th21, NHMW 113488); C: Krabi Province, 1.7 km SE of Ao Luek Tai, Simon Aiken leg., 19 Mar. 2020, coll. SA.