Dioryx feuangensis Jirapatrasilp & Inkhavilay 2026, sp. nov.
Year: 2026
Type: article
Abstract: Dioryx feuangensis Jirapatrasilp & Inkhavilay sp. nov. Fig. 4 Type material. Holotype. Laos • 1 shell, SH = 9.3 mm, SW = 8.3 mm; Vientiane Province, Feuang District, Pha Thor (loc. MF 13); 18°42'08.6"N, 102°07'54.5"E; 225 m a. s. l.; 10 Oct. 2024; leg. CU - NUOL expedition team; CUMZ 14477 (Fig. 4 A). Paratypes. Laos • 33 shells; same data as for holotype; CUMZ 14478 • 3 shells; same data as for holotype; NHMUK 20260369 • 3 shells; same data as for holotype; SMF. Other material. Laos • 224 shells; Vientiane Province, Feuang District, Pha Reung (loc. MF 14); 18°44'20.4"N, 102°07'02.9"E; 360 m a. s. l.; 10 Oct. 2024; leg. CU - NUOL expedition team; CUMZ 14479 (Fig. 4 B). Diagnosis. Shell conical, globular. Spire ~ ¼ of shell height. Spiral striation lacking on the entire shell. R 1 ~ 2 ½ whorls; R 2 ~ ½ whorl, with indistinct ribs; the end of R 2 narrower, appearing as a broad constriction between R 2 and apertural tube. Peristome double with prominent, expanding outer peristome with irregular perimeter. Umbilicus open. Differential diagnosis. Dioryx feuangensis sp. nov. is distinct in having a prominent, expanding outer peristome with irregular perimeter. Apart from this character, this new species is similar to D. compactus (Bavay & Dautzenberg, 1900) (Páll-Gergely et al. 2017: fig. 4 c) in its globular shell shape with a SW: SH ratio approaching 1, but the new species differs by a larger shell (SH 8.5–9.5 mm, SW 8.0– 8.5 mm vs SH 4.7 mm, SW 4.2 mm) with matt surface. This new species is also similar to D. rosea (Bavay & Dautzenberg, 1900) in its shell colour and shape, but the new species differs by a lack of spiral striation on the entire shell, and a less protruding inner peristome. The new species’ matt shell surface matches more to D. globuloides Zilch, 1957 (Páll-Gergely et al. 2017: fig. 4 d), but the latter species is smaller, with a shorter sutural tube at R 2, and the outer peristome is expanded to a lesser extent. Dioryx feuangensis sp. nov. is similar to D. requiescens (Mabille, 1887) in its R 2 length, but D. feuangensis sp. nov. is more globular in shell shape, and has an outer peristome with irregular perimeter, and an apertural tube opening parallel to the horizontal axis of the shell. Dioryx requiescens is less globular (SW: SH ratio <1), and has a regular outer peristome, and an apertural tube opening obliquely downward to the horizontal axis of the shell. Description. Shell conical, globular, solid, matt, yellowish to pale crimson, SH 8.5–9.5 mm, SW 8.0– 8.5 mm (n = 10). Shell outline round in apical view, spire ~ ¼ of shell height. Whorls ~ 4 ½, last whorl large, round; spiral striation lacking on the entire shell. Protoconch low, ~ 1 ½ whorls, glossy, smooth. R 1 ~ 2 ½ whorls; R 2 ~ ½ whorl, with indistinct ribs; the end of R 2 narrower, appearing as a broad constriction between R 2 and apertural tube. R 3 absent; apertural tube expanding from the end of R 2, opening parallel to horizontal axis of the shell. Aperture round; peristome double with prominent outer peristome with irregular perimeter. Inner peristome blunt, slightly protruding. Outer peristome not thickened, expanded, not reflected. Umbilicus open. Operculum unknown. Etymology. The species name is derived from the type locality, Feuang District in Vientiane Province, Laos. Distribution. Known only from the limestone areas in Feuang District, Vientiane Province, Laos. Remarks. The lack of spiral striation on the entire shell and a prominent, expanding outer peristome with irregular perimeter 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: W7204206487