Dicharax pongrati Jirapatrasilp & Tongkerd, 2021

Jirapatrasilp, Parin, Pall-Gergely, Barna, Sutcharit, Chirasak & Tongkerd, Piyoros, 2021, The operculate micro land snail genus Dicharax Kobelt & Moellendorff, 1900 (Caenogastropoda, Alycaeidae) in Thailand, with description of new species, Zoosystematics and Evolution 97 (1), pp. 1-20 : 1

Dicharax pongrati Jirapatrasilp & Tongkerd sp. nov. Figs 6D , 7C , 12D

Type material.

Holotype CUMZ 7430/1 (Fig. 12D ), paratypes CUMZ 7430/2 (56 shells; Figs 6D , 7C ), HNHM (2 shells), NHMUK 20200328 (2 shells) and SMF (2 shells) from Doi Chiang Dao, Chiang Mai Province, Thailand, 19°14'26.7"N, 98°52'49.8"E, 24-28 May 1997, coll. S. Panha, J.B. Burch, P. Dumrongrojwattana.

Diagnosis.

Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical. Spire ca. ¼ of shell height. R1 with regular, thread-like ribs; R2 three times longer than R3; R2 with ca. 76 ribs. R3 strongly reduced, without swelling. Aperture round. Inner peristome with two shallow indentations. Outer peristome expanded, slightly reflected. Umbilicus elliptical. Operculum multispiral, with or without elevated lamella.

Description.

Shell medium-sized (SH up to 2.3 mm, SW up to 4.4 mm), lenticular, depressed-conical, solid, translucent, yellowish to pale orange. Shell outline oval in apical view, spire ca. ¼ of shell height. Whorls ca. 4 and 1/8. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 1¾ whorls with fine, regular, thread-like ribs; with ca. 17 ribs in ¼ whorl adjoining R2, ribs more elevated and sharper near suture and flatter near umbilicus and at the edge of body whorl. Boundary between R1 and R2 distinct as R2 contains denser and thicker ribs than R1; R2 with ca. 76 ribs that are curved towards aperture; R2 ca. 1/3 whorl, three times longer than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 strongly reduced, without swelling, practically the constriction continues directly to outer peristome. Aperture round; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome slim, slightly protruding, with two shallow indentations. Outer peristome thickened, expanded, slightly reflected, multilayered (visible in lateral view). Umbilicus elliptical, open, approximately one third of shell width. Operculum either thin with low lamella or thick with elevated lamella.

Etymology.

In honor of Pongrat Dumrongrojwattana, a Thai malacologist who has studied micro land snails of Thailand and was one of the collectors of this new species.

Distribution.

The new species is known only from the type locality in Chiang Mai Province, Thailand.

Remarks.

Differs from the sympatric and similar depressed-conical D. pratatensis in having a wider and more depressed shell, a much longer R2, a shorter R3 without a swelling and two shallow indentations at the inner peristome.

Figures

Figure 6. Synoptic view of the eight Dicharax taxa in Thailand. A. Dicharax omissus, specimen CUMZ 7426 (gold plated); B. Dicharax pratatensis, specimen CUMZ 7427; C. Dicharax panhai sp. nov., paratype CUMZ 7429 / 2; D. Dicharax pongrati sp. nov., paratype CUMZ 7430 / 2; E. Dicharax notus, specimen CUMZ 7425; F. Dicharax burchi sp. nov., paratype CUMZ 7428 / 2; G. Dicharax borealis sp. nov., paratype CUMZ 5072 / 2; H. Dicharax cucullatus, specimen CUMZ 7421.

Figure 7. Close-up images of the aperture showing the operculum in situ. A, B. Dicharax notus, specimens CUMZ 7425; A. Without lamella; B. With elevated lamella; C. Dicharax pongrati sp. nov., paratype CUMZ 7430 / 2, without lamella, probably lost due to corrosion.

Figure 12. A-C. Dicharax panhai sp. nov. A. Holotype CUMZ 7429 / 1; B. Paratype CUMZ 7429 / 2; C. paratype SMF 331452 (paratype of " Alycaeus pratatensis Cy 003 " from Tham Pratat, Erawan National Park, Kanchanaburi Province, Thailand). D. Dicharax pongrati sp. nov., holotype CUMZ 7430 / 1 Close-up images of the aperture not to scale. Photo: B. Pall-Gergely, courtesy Ronald Janssen (C.).