Chamalycaeus hirpex 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 : 11-12

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

Figs 6–8

Material examined. Holotype: Thailand, Krabi Province, N of Krabi, Wat Tham Suea ( Tiger Cave Temple), along steps to the cave, 8°7.603’N, 98°55.466’E, ca. 90 m a.s.l. (locality code: Th 11), Sep. 2007, A. Reischütz leg., at base of limestone rocks, NHMW 113485 (D: 2.42 mm, H: 1.53 mm) . Paratypes: 12 shells, same data as holotype, RE ; 42 shells, Thailand, Krabi Province, Railay Beach West, Viewpoint Hill , 8°0.511’N, 98°50.248’E, ca. 30 m a.s.l. (locality code: Th 14), Sep. 2007, A. Reischütz leg., at base of limestone rocks, RE ; 2 shells, same data as preceding, CUMZ 5268 ; 1 shell ( Fig. 6C ), Thailand, Krabi Province, E of Krabi, Khao Khanab Nam limestone hill, 8°4.707’N, 98°55.263’E, ca. 2 m a.s.l. (locality code: Th 15), Sep. 2007, A. Reischütz leg., at base of limestone rocks just above tidal influence, NHMW 113486 ; 17 shells, same data as preceding, RE ; 3 shells, limestone hill at river Khanab Nam (Krabi Yai) at the northeastern city limits of Krabi, by the road Thanon Lan Gu ( Mueang Kao ), ca. 400 m E of crossing with road Thanon Thong Chai, S of road, 8°5.817’N, 98°55.068’E, ca. 10 m a.s.l. (locality code: Th 17), Mar. 2010, A. Reischütz leg., at base of limestone rocks, RE ; 2 shells, Thailand, Krabi Province, Wat Tham Sua , 8°7.567’N, 98°55.496’E, 40 m a.s.l. (locality code: 2015/34), 21 Feb. 2015, A. Hunyadi leg., HA . Other material: 7 juvenile /broken shells; same data as holotype, RE ; 6 juvenile /broken shells, Thailand, Krabi Province, Railay Beach West, Viewpoint Hill ; 8°0.511’N, 98°50.248’E; ca. 30 m a.s.l. (locality code: Th 14), Sep. 2007, A. Reischütz leg., at base of limestone rocks, RE ; 4 juvenile /broken shells, Thailand, Krabi Province, E of Krabi, Khao Khanab Nam limestone hill, 8°4.707’N, 98°55.263’E, ca. 2 m a.s.l. (locality code: Th 15), Sep. 2007, A. Reischütz leg., at base of limestone rocks just above tidal influence, RE ; 2 juvenile /broken shells, Thailand, Krabi Province, limestone hill at river Khanab Nam (Krabi Yai) at northeastern city limits of Krabi, by road Thanon Lan Gu ( Mueang Kao ), ca. 400 m E of crossing with road Thanon Thong Chai, S of road, 8°5.817’N, 98°55.068’E, ca. 10 m a.s.l. (locality code: Th 17), Mar. 2010, A. Reischütz leg., at base of limestone rocks, RE ; 3 juvenile /broken shells, Thailand, Krabi Province, Wat Tham Sua , 8°7.567’N, 98°55.496’E, 40 m a.s.l. (locality code: 2015/34), 21 Feb. 2015, A. Hunyadi leg., HA ; 2 broken shells, Thailand, Krabi Province, granite rock in evergreen forest at Tone Nga Chang Waterfall, Cha Lung, Hat Yai , Songkhla, 6°56.810’N, 100°13.895’E (locality code: AC21 ), C. Sutcharit et al. leg., CUMZ 5271 ( Fig. 8 , identification questionable, not shown on Fig. 3 ).

Etymology. The specific epithet refers to the R2 rib morphology, which, with the numerous tooth-like projections, is reminiscent of a harrow, an agricultural tool consisting of a framework with teeth used to break up plowed land ( hirpex in Latin).

Diagnosis. A small Chamalycaeus species with R2+R3 shorter than a quarter whorl and R2 with serrulate ribs.

Description (based on the type series). Shell off-white, light grey to slightly yellowish; shell outline rounded in dorsal view, R2 conspicuously bulging/angled in dorsal view, but variable in some populations; spire rather depressed, but variable among populations, low conical; body whorl rounded or rather parabolic; protoconch elevated, finely granular, spiral striation lacking, 1.5 whorls ( Figs 7C–D ); R1 ca. 1.5 whorls, first ca. 0.75 whorl dominated by fine ribbing that gradually increases strength toward the R1 termination; spiral striation as strong as radial ribs at end of R1, while due to domination of ribs at end of R1, relative strength of spiral striae decreases; R1 and R2 boundary conspicuous due to denser R2 ribs; R2+R3 less than a quarter whorl (ca. 70–80˚); R2 bulging, forming a blunt angle in dorsal view, and rounded in apertural view; R2 ribs lamella-like, rather low, characteristically serrate (i.e. a series of tiny spikes pointing anteriorly, see Figs 7A–B ), ca. 24–26 R2 ribs present; R2 and R3 of comparable lengths or R2 slightly shorter; R3 with spiral striation and weaker ribs than R1; boundary between R2 and R3 distinct due to lower R3 ribs, although constriction is shallow; aperture very strongly oblique to shell axis; rounded, with very weak upper (parieto-palatal) incision, a weak basal incision occasionally also indicated; boundary between inner and outer peristomes distinct; inner peristome protruding, rather sharp and relatively thin; outer peristome expanded except in umbilical area; umbilicus relatively wide, over one third shell width.

A cross-sectional view of R2 was examined in one specimen ( Figs 7E–H ): anterior crust forms an elevated rib, which forms a series of hollow spikes (visible in cross-sectional image as widened tip) toward aperture, posterior crust low, adnate to anterior crust, which slightly folds over posterior crust; cross-sectional view of microtunnels nearly rounded, drop shaped, or somewhat triangular.

Measurements. D: 2.00– 2.61 mm, H: 1.32–1.67 mm.

Operculum. Strongly concave, outer surface with no structures, covered with thick mud layer; inner side with elevated central nipple ( Fig. 6B ).

Differential diagnosis. The reticulated R2 sculpture distinguishes this species from all congeners except for C. serratus n. sp. See that species for comparisons.

Distribution. This new species is known from four populations occurring in Krabi Province, Thailand ( Fig. 3 ).

Remarks. The examined populations show a degree of morphological variability, see Table 1 .

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 6. Chamalycaeus hirpex Páll-Gergely & A. Reischütz, n. sp. A: holotype (NHMW 113485); B: operculum, paratype from the type locality (site Th11, sp3); C: paratype (site Th15 NHMW 113486).

FIGURE 7. Chamalycaeus hirpex Páll-Gergely & A. Reischütz, n. sp. A–D: holotype (NHMW 113485); E–H: paratype from the type locality (RE). Abbreviations: a—anterior crust; p—posterior crust; t—microtunnel.

FIGURE 8. Chamalycaeus cf. hirpex Páll-Gergely & A. Reischütz, n. sp. CUMZ 5271.