Pincerna panhai Jirapatrasilp & Inkhavilay 2026, sp. nov.

Information from the abstract

Pincerna panhai Jirapatrasilp & Inkhavilay sp. nov. Figs 10, 11 Type material. Holotype. Laos • 1 shell, SH = 3.9 mm, SW = 4.2 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 14486 (Fig. 10). Paratypes. Laos • 5 shells; same data as for holotype; CUMZ 14487 (Fig. 11 A) • 2 shells; same data as for holotype; NHMUK 20260370 • 2 shells; same data as for holotype; SMF. Other material. Laos • 5 shells; Vientiane Province, Feuang District, limestone hill opposite to Xinxayyaram Temple (loc. MF 8); 18°32'41.8"N, 101°58'47.0"E; 280 m a. s. l.; 8 Oct. 2024; leg. CU - NUOL expedition team; CUMZ 14488 (Fig. 11 B) • 5 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 14489. Diagnosis. R 1 ~ 1 ¾ whorls with regular, sharp radial ribs. R 2 ~ ¼ whorl and nearly as long as R 3; with ~ 25 thicker, blunter, and more close-set ribs. R 3 ~ 3 ribs; apertural tube coiling more or less parallel to horizontal axis of the shell, expanding near the end of the aperture. Inner peristome blunt, slightly protruding. Outer peristome thickened, multilayered, expanded, not reflected. Umbilicus closed by the expanded columellar extension of outer peristome. Differential diagnosis. Among the ribbed species of Pincerna, P. panhai sp. nov. is similar to P. costulosus (Bavay & Dautzenberg, 1912) (Páll-Gergely 2023 b: figs 8, 9) in its sharp, spaced radial ribs, and an umbilicus closed by the expanded columellar extension of outer peristome. However, the new species has a wider shell shape, a longer R 2 (~ 25 vs 6–14 ribs), and R 3 with sharper, more distinct ribs. The sharp, distinct R 3 ribs of the new species match more with P. acroptychia Páll-Gergely, 2023 (Páll-Gergely 2023 b: fig. 5 a – e), but the new species has a wider shell shape, less close-set radial ribs, and a longer R 2 (~ 25 vs 16 ribs). Pincerna panhai sp. nov. is also similar to P. viginticostatus Páll-Gergely, 2023 (Páll-Gergely 2023 b: fig. 14 a – f) in shell shape and R 2 length, and a close umbilicus. However, the new species has sharper and less close-set radial ribs, and less R 3 ribs (~ 3 vs 8 ribs). Description. Shell conical, globose, solid, translucent, whitish to pale crimson, SH 3.8–4.0 mm, SW 4.1–4.3 mm (n = 10). Shell outline round in apical view, spire ~ ¼ of shell height. Whorls ~ 4 ¼, last whorl large, round; spiral striation lacking on the entire shell. Protoconch high, ~ 1 ¾ whorls, glossy, smooth. Radial ribs strong, regular, starting from R 1, continuing to the end of aperture. R 1 ~ 1 ¾ whorls; with ~ 9 sharp ribs in ¼ whorl adjoining R 2. Boundary between R 1 and R 2 distinct as R 2 contains more close-set and thicker, blunter ribs than R 1. R 2 ~ ¼ whorl and nearly as long as R 3; with ~ 25 ribs; ribs consistently thickened throughout. Boundary between R 2 and R 3 distinct as R 3 abruptly expanded, and contains much less close-set and sharper ribs than R 1 and R 2. R 3 with fine growth lines and ~ 3 ribs; coiling more or less parallel to horizontal axis of the shell, expanding near the end of the aperture. Aperture round; peristome double with prominent outer peristome. Inner peristome blunt, slightly protruding. Outer peristome thickened, multilayered (visible in lateral view), expanded, not reflected. Umbilicus closed by the expanded columellar extension of outer peristome. Operculum thin, translucent; multispiral ridges not elevated. Etymology. The species name is in honour of Prof. Somsak Panha, a prominent Thai malacologist and our beloved professor, who supervised the taxonomic and systematic study of land snails and other terrestrial invertebrates in Laos, as well as other countries in mainland Southeast Asia. Distribution. Known only from the limestone areas in Feuang District, Vientiane Province, Laos. Remarks. The occurrence of regular, sharp radial ribs, the number range of R 2 and R 3 ribs, and a close umbilicus are consistent across all specimens of this new species, suggesting that these are important diagnostic characters.

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