Dicharax feuangensis Jirapatrasilp & Inkhavilay 2026, sp. nov.
Year: 2026
Type: article
Abstract: Dicharax feuangensis Jirapatrasilp & Inkhavilay sp. nov. Fig. 8 Type material. Holotype. Laos • 1 shell. SH = 1.0 mm, SW = 1.9 mm; Vientiane Province, Feuang District, unnamed limestone hill (loc. MF 1); 18°40'29.2"N, 102°02'18.4"E; 320 m a. s. l.; 7 Oct. 2024; leg. CU - NUOL expedition team; CUMZ 14483 (Fig. 8 A). Paratypes. Laos • 1 shell; same data as for holotype; CUMZ 14484 (Fig. 8 B). Diagnosis. Shell lenticular, depressed-conical. Spire ~ 1 / 5 of shell height. R 1 ~ 1 ½ whorls with regular, sharp radial ribs. R 2 very short; with ~ 10 ribs; ribs consistently thickened throughout. R 3 ~ 1 / 5 whorl with ~ 21 ribs. Apertural tube coiling parallel to horizontal axis of the shell, slightly expanding near the end of the aperture. Inner peristome slim, very slightly protruding. Outer peristome thickened, slightly expanded at the columellar corner, not reflected. Differential diagnosis. Among the tiny Dicharax species (SH and SW <2 mm), D. feuangensis sp. nov. is most similar to D. parvulus (Möllendorff, 1887) (Páll-Gergely et al. 2021: fig. 31 b) in its low spire, short R 2, and a nearly consistent radial rib density along the teleoconch, rendering the boundaries between R 1 and R 2, and R 2 and R 3 indistinct. However, the new species has a longer R 3 with more ribs (21 vs 14), a less widening R 3, and an outer peristome with only a slight expansion at the columellar corner. This new species is also similar to D. abdoui Páll-Gergely, 2017 (Páll-Gergely et al. 2017: fig. 6) in R 2 length, but D. feuangensis sp. nov. has distinct higher elevated radial ribs throughout R 1 – R 3, and a smooth protoconch, while D. abdoui has nearly smooth R 1 and R 3, and a protoconch with extremely fine pits arranged in spiral rows. Description. Shell lenticular, depressed-conical, solid, translucent, SH 1.0 mm, SW 1.9 mm (n = 2). Shell outline oval in apical view, spire ~ 1 / 5 of shell height. Whorls ~ 3 ½; spiral striation lacking on the entire shell. Protoconch low, ~ 1 ¾ whorls, smooth. Radial ribs strong, regular, starting from R 1, becoming sharper, thicker, and less close-set toward the end of aperture. R 1 ~ 1 ½ whorls with ~ 33 ribs in ¼ whorl adjoining R 2. Boundary between R 1 and R 2 indistinct as R 2 contains nearly the same rib density and thickness as in R 1. R 2 very short; with ~ 10 ribs; ribs consistently thickened throughout. Boundary between R 2 and R 3 indistinct as R 3 contains nearly the same rib density and thickness as in R 2. R 3 ~ 1 / 5 whorl with ~ 21 ribs; apertural tube coiling parallel to horizontal axis of the shell, slightly expanding near the end of the aperture. Aperture round. Peristome double with regular outer peristome. Inner peristome slim, slightly protruding. Outer peristome thickened, multilayered (visible in lateral view), slightly expanded at the columellar corner, not reflected. Umbilicus elliptical, open, approximately 1 / 3 of shell width. Operculum thin, translucent; multispiral ridges not elevated. Etymology. The species name is derived from the type locality, Feuang District in Vientiane Province, Laos. Distribution. Known only from the type locality in Feuang District, Vientiane Province, Laos. Remarks. The length and the less widening of R 3, and a smooth protoconch are consistent across all specimens of this new species, suggesting that these are important diagnostic characters.
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7204205688