Dicharax borealis 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 borealis Jirapatrasilp & Pall-Gergely sp. nov. Figs 6G , 9

Type material.

Holotype CUMZ 5072/1 (Fig. 9 ), paratypes CUMZ 5072/2 (2 shells; Fig. 6G ), NHMUK 20200325 (1 shell) and SMF (1 shell) from Tham Ban Luang, Doi Ang Khang, Chiang Mai Province, Thailand, 19°52'13.7"N, 99°02'44.1"E, 17 Mar. 2000, coll. S. Panha, P. Tongkerd.

Diagnosis.

Shell medium-sized (SH up to 2.7 mm, SW up to 4.4 mm), depressed-conical. Spire ca. 1/6 of shell height. R1 with regular ribs; R2 twice longer than R3; R2 with ca. 72 ribs. R3 with very low, elongated swelling. Aperture oval. Inner peristome thickened, with three very shallow indentations, always without parieto-columellar indentation. Outer peristome expanded, not reflected. Umbilicus round.

Description.

Shell medium-sized (SH up to 2.7 mm, SW up to 4.4 mm), depressed-conical, solid, translucent, pale yellowish. Shell outline oval in apical view, spire ca. 1/6 of shell height. Whorls ca. 4¼. Protoconch low, ca. two whorls, glossy and smooth. R1 ca. 1¾ whorls, with fine, regular ribs; with ca. 21 ribs in ¼ whorl adjoining R2, ribs sharper near suture and inside umbilicus than in middle of body whorl. Boundary between R1 and R2 distinct as R2 contains more close-set and thicker ribs than R1; R2 with ca. 72 ribs that are curved towards aperture; R2 ca. 1/3 whorl and twice longer than R3. Boundary between R2 and R3 distinct due to shallow constriction; R3 with fine growth lines; with very low and elongated swelling. Aperture oval; slightly oblique to shell axis. Peristome double with regular outer peristome. Inner peristome thick, expanded, with three very shallow indentations, always without parieto-columellar indentation. Outer peristome thinner, expanded, not reflected, multi-layered (visible mostly in lateral view). Umbilicus round, open, approximately one third of shell width. Operculum unknown.

Etymology.

The specific epithet " Dicharax borealis " refers to the occurrence of the new species from the northern mountain of Thailand.

Distribution.

Known only from the type locality in Chiang Mai Province, Thailand.

Remarks.

Differs from the sympatric D. cucullatus in having a wider shell, a rather oval outline, a shorter R3 with very low and elongated swelling, a less fringed and oval aperture and an inner peristome with three very shallow indentations, always without any parieto-columellar indentation.

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 9. Dicharax borealis sp. nov., holotype CUMZ 5072 / 1.