Chamalycaeus spiratus 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 : 21

Chamalycaeus spiratus Páll-Gergely n. sp.

Fig. 13

Material examined. Holotype: Thailand, Rayong Province, limestone range Khao San Ta , 2.0 km W of Ban Syaek Batan, 12°58.75’N, 101°40.00’E, 150 m a.s.l., 25 Apr. 1987, F.G. Thompson leg., UF 279157 (D: 1.8 mm, H: 1.16 mm) . Paratypes: 5 shells, same data as holotype, UF 551217 .

Etymology. This new species is named for its conspicuous spiral striae.

Diagnosis. A tiny Chamalycaeus species with strong, conspicuous spiral striations on entire teleoconch, R2+R3 slightly shorter than a quarter whorl, and distance between the edges of the inner and outer peristomes is great, outer peristome not reflected.

Description. Shell off-white to yellowish-corneous, probably somewhat translucent when fresh; shell outline rounded in dorsal view; spire slightly elevated, low conical; body whorl rounded; protoconch somewhat elevated, glossy, finely granular, spiral striae lacking, 1.5 whorls; R1 of 1.25–1.5 whorls, with very strong, broad spiral striae on last 0.75–1.0 whorl, preceding area rather smooth; last ca. half whorl of R1 with strong but low ribs, similar strength to spiral striae, widely and irregularly spaced; boundary between R1 and R2 distinct due to change in rib density; R2 ribs curve toward aperture, spaces between ribs approximately as wide as ribs; ca. 18–20 ribs present; R2+R3 less than quarter whorl (ca. 70–80˚), comparable in length; boundary between R2 and R3 distinct due to change in rib morphology, constriction lacking; R3 practically without swelling, with similar spiral striae to that of R1, ribs virtually absent, replaced by very fine, weak growth lines; aperture slightly oblique to shell axis, round; boundary between inner and outer peristomes conspicuous, inner peristome strongly protruding and slightly expanded; edge of outer peristome thin, expanded weakly toward umbilicus, not reflected; umbilicus relatively narrow, approximately one third of shell width.

Measurements. 1.72–1.93 mm, H: 1.07–1.16 mm.

Operculum. Unknown.

Differential diagnosis. The small size, prominent, thin outer peristome, strong ribs and spiral striae distinguish this species from all other congeners. The most similar species in size and sculpture are Chamalycaeus microconus ( Möllendorff, 1887) (examined material: Malakka: Bukit Pondong (Perak), SMF 109493, lectotype, and SMF 109494, 2 paralectotypes) and Chamalycaeus mixtus Zilch, 1957 (examined material: Malakka: Bukit Pondong (Perak), SMF 109510, holotype, and SMF 109511, 4 paratypes) from the Malay Peninsula (Bukit Pondong), but they have higher spires, comparatively larger apertures, and shorter R3s. For comparisons, see photos in Páll-Gergely et al. (2020).

Distribution. This new species is known only from the type locality ( Fig. 5 ).

Figures

FIGURE 5. Distribution of alycaeid species. Inverted empty triangle: Dicharax cyclostoma Páll-Gergely, n. sp., empty triangle: Chamalycaeus spiratus Páll-Gergely, n. sp., filled triangle: Metalycaeus bicarinatus Páll-Gergely & Hunyadi, n. sp., inverted filled triangles: Chamalycaeus erawan Páll-Gergely & Hunyadi n. sp., empty circles: Metalycaeus aries Páll-Gergely & Auffenberg, n. sp., filled circles: Metalycaeus heudei (Bavay & Dautzenberg, 1900) (the one in the north indicates the type locality of Alycaeus kengtungensis Godwin-Austen, 1914), square: Metalycaeus pygmachos Páll-Gergely & Hunyadi, n. sp.

FIGURE 13. Chamalycaeus spiratus Páll-Gergely, n. sp., holotype (UF 279157).