Chamalycaeus serratus Páll-Gergely & Auffenberg, 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 : 19-20

Chamalycaeus serratus Páll-Gergely & Auffenberg n. sp.

Fig. 12

Material examined. Holotype: Thailand, Nakhon Si Thammarat Province, Khao Luang Park, 15.2 km S junction Highways 4186 and 4188, 1.3 km S Park Headquarters, 8°44’N, 99°43’E, 200 m a.s.l., 16 Apr. 1988, K. Auffenberg leg., UF 345204 (D: 2.35 mm, H: 1.67 mm).

Etymology. Named for the serrated R2 ribs (Latin derivative serratus , notched like a saw).

Diagnosis. A small Chamalycaeus species with R2+R3 being longer than a quarter whorl, R3 twice as long as R2, which bears characteristically serrulate R2 ribs.

Description. Shell off-white, although dead-collected; shell outline rounded/slightly oval in dorsal view; spire elevated, conical; body whorl rounded with some depression inwardly in dorso-basal region; protoconch 1.5 whorls, elevated, finely granular, without spiral striation; R1 slightly more than 1.5 whorls, first ca. 0.75 whorl dominated by fine ribs, gradually becoming stronger toward R1 termination; spiral striation as strong as radial ribs at R1 termination; boundary between R1 and R2 conspicuous because of denser R2 ribs; R2+R3 more than quarter whorl (approximately 100˚); R2 ribs lamella-like, rather low, characteristically serrate with series of tiny spikes pointing anteriorly, ca. 28 R2 ribs present; R3 ca. twice as long as R2; R3 with rather strong spiral striation and weaker ribs than R1; boundary between R2 and R3 clear due to less pronounced R3 ribs, although constriction is shallow; aperture strongly oblique to shell axis, rounded; boundary between inner and outer peristomes distinct; inner peristome protruding, narrow, and relatively thin; outer peristome expanded, especially in basal and upper palatal directions; umbilicus narrow, ca. one fourth of shell width.

Measurements. D: 2.35 mm, H: 1.67 mm.

Operculum. Unknown.

Differential diagnosis. This new species is very similar to Chamalycaeus hirpex n. sp. in terms of R2 morphology. However, it differs from that species in the long R3, which has an elongated, blunt swelling, and a more expanded aperture.

Distribution. This new species is known only from the type locality ( Fig. 3 ).

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 12. Chamalycaeus serratus Páll-Gergely & Auffenberg, n. sp., holotype (UF 345204).