Dicharax panhai Jirapatrasilp & Pall-Gergely, 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 panhai Jirapatrasilp & Pall-Gergely sp. nov. Figs 6C , 12A-C

Dicharax pratatensis - Páll-Gergely et al. 2020b: 71, 72.

Type material.

Holotype CUMZ 7429/1 (Fig. 12A ), paratypes CUMZ 7429/2 (16 shells; Figs 6C , 12B ), HNHM (2 shells), NHMUK 20200327 (2 shells), paratypes of " Alycaeus pratatensis Cy 003" FMNH (2 shells), SMF 331452 (2 shells; Fig. 12C ) and UMMZ (2 shells) from Tham Pratat, Erawan National Park, Kanchanaburi Province, Thailand, 14°23'50.8"N, 99°04'56.3"E, 230 a.s.l., 26 Oct. 1996, coll. S. Panha.

Diagnosis.

Shell small (SH up to 2.4 mm, SW up to 3.1 mm), depressed-conical with triangular dorsal side and widened, sigmoid last whorl. Spire ca. 1/3 of shell height. R1 with regular, thread-like ribs; R2 twice shorter than R3; R2 with ca. 18 ribs. R3 with blunt central swelling. Aperture round. Inner peristome thick, protruding. Outer peristome expanded, not reflected. Umbilicus elliptical.

Description.

Shell small (SH up to 2.4 mm, SW up to 3.1 mm), depressed-conical with triangular dorsal side and widened, sigmoid last whorl; solid, worn out white; the exact color of non-weathered (fresh) shells unknown. Shell outline oval in apical view, spire ca. 1/3 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. 14 ribs in ¼ whorl adjoining R2, ribs sharper near suture and flatter near umbilicus. Boundary between R1 and R2 distinct as R2 contains more close-set ribs than R1; R2 with ca. 18 ribs that are curved towards aperture; R2 ca. 1/8 whorl, twice shorter than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 initially coils horizontally forming a flat base, but aperture strongly descent being strongly oblique to shell axis; R3 mostly smooth with indistinct growth lines that become stronger near aperture; with blunt central swelling. Aperture round; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome thick, protruding. Outer peristome slightly expanded, not reflected, multi-layered (visible mostly in lateral view). Umbilicus elliptical, open, slightly more than one third of shell width. Operculum unknown.

Etymology.

In honor of Prof. Somsak Panha, a prominent Thai malacologist and our beloved professor who initiated the taxonomic and systematic study of land snails and other terrestrial invertebrates in Thailand and surrounding areas of mainland Southeast Asia.

Distribution.

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

Remarks.

Similar to D. pratatensis from Doi Chiang Dao, Chiang Mai Province, Thailand in having a depressed-conical shell shape and R3 with blunt swelling, but differs in having a conical apical part on a wide shell base, less distinct ribs of R1 and shorter R2 with less ribs. The short R2 and breathing tube is also exhibited in D. abdoui Páll-Gergely in Páll-Gergely et al., 2017 from Khammouane Province, Laos and D. stuparum from Chiang Rai Province, Northern Thailand, but D. panhai sp. nov. is larger, comprises more whorls, has a more elevated spire and a larger last whorl ( Páll-Gergely et al. 2017, Páll-Gergely and Hunyadi 2018).

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 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.).