Dicharax mirounga Páll-Gergely, 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 : 31

Dicharax mirounga Páll-Gergely n. sp.

Fig. 23

Material examined. Holotype: Thailand, Tak Province, Knoll 7 km E of Ban Huei Hin Fond, 16°46.350’N, 98°40.383’E, 610 m a.s.l., 02 May 1987, F.G. Thompson leg., UF 347421 (D: 3.13 mm, H: 2.08 mm).

Etymology. The R3 shape of this species is reminiscent of the large proboscis of elephant seal males (genus Mirounga) (see Galimberti et al. 2019).

Diagnosis. A medium-sized Dicharax species with glossy R1 having some widely-spaced, typical Dicharax -ribs, long R3 with an elongated swelling, strongly expanded outer peristome, and narrow umbilicus.

Description. Shell white, with slightly yellowish colouration; shell outline oval in dorsal view; spire elevated, conical, body whorl rounded; protoconch low, glossy, slightly more than 1.25 whorls; R1 of 1.75 whorls, glossy, with widely-spaced ribs, strong only near suture and in umbilicus, represented as very fine axial lines on edge of peristome; boundary between R1 and R2 conspicuous due to dense R2 ribs; R2 ribs curved toward aperture, ca. 28 R2 ribs present; spaces between R2 ribs narrower than ribs; R2+R3 more than quarter whorl (ca. 110˚); R2 approximately half length of R3; R3 glossy, smooth, with very fine growth lines; boundary between R2 and R3 conspicuous due to change in sculpture, although constriction shallow; entire R3 with an elongated, inflated swelling reminiscent of an elephant seal proboscis; aperture strongly oblique to shell axis, round; boundary between inner and outer peristomes distinct; inner peristome somewhat protruding, rather thin, outer peristome extremely expanded, forming uniformly wide rim around aperture, slightly reflected over umbilicus, notched at the parieto-palatal edge; umbilicus very narrow.

Measurements. D. 3.13 mm, H: 2.08 mm.

Operculum. Unknown.

Differential diagnosis. There are no other species recorded from Thailand, Myanmar, and neighbouring areas with such an expanded outer peristome. This trait, combined with the relatively small size, elevated spire, and smooth R1 makes this species easily recognizable.

Distribution. This new species is known only from the type locality ( Fig. 17 ).

Figures

FIGURE 17. Distribution of alycaeid species in northern Thailand and Myanmar. filled circle: Dicharax admirandus Páll- Gergely & Auffenberg, n. sp., empty square: Dicharax ebrius Páll-Gergely & Auffenberg, n. sp., filled triangle: Dicharax gnomus Páll-Gergely, n. sp., filled square: Dicharax mirounga Páll-Gergely, n. sp., inverted empty triangles: Dicharax verruco- sus Páll-Gergely & Hunyadi n. sp., rhombus: Dicharax stuparum Páll-Gergely & Hunyadi, 2018, empty triangle: Metalycaeus anas Páll-Gergely & A. Reischütz, n. sp.

FIGURE 23. Dicharax mirounga Páll-Gergely, n. sp., holotype (UF 347421).