Dicharax notus (Godwin-Austen, 1914)

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 notus (Godwin-Austen, 1914) Figs 4C, D , 5B , 6E , 7A, B

Alycaeus notus Godwin-Austen, 1914: 411, pl. 155, fig. 12. Type locality: Fort Stedman, Burma [Maing Thauk or Mine Thauk located in the east side of Inle Lake south of Nyaungshwe, Nyaungshwe Township, Taunggyi District, Shan State, Myanmar].

Alycaeus (Dicharax) notus - Gude 1921: 262.

Dicharax notus - Páll-Gergely et al. 2020b: 69.

Type material examined.

Syntypes NHMUK 1903.7.1.3065 from Fort Stedman (15 shells; Fig. 4C ).

Other material examined.

CUMZ 7425 from Tham Luang Sa Koen , Nan Province, Thailand, 19°22'00.1"N, 100°32'28.4"E, 19 Jan. 2017, coll. C. Sutcharit, A. Pholyotha (174 shells and 13 specimens in ethanol; Figs 4D , 5B , 6E , 7A, B ) .

Diagnosis.

Shell small (SH up to 2.2 mm, SW up to 3.6 mm), depressed-conical. Spire ca. 1/5 of shell height. R1 with regular ribs; R2 as long as or shorter than R3; R2 with 48-50 ribs. R3 with low blunt central swelling, more elevated in newly examined population. Aperture round. Inner peristome without indentation, with parieto-columellar angle in newly examined population. Outer peristome expanded, reflected. Umbilicus round. Operculum multispiral either with or without elevated lamella.

Distribution.

Shan State, Myanmar ( Gude 1921), and Nan Province, Thailand.

Remarks.

Similar to D. cristatus ( Möllendorff, 1886) from China and Vietnam as well as D. depressus (Bavay & Dautzenberg, 1912) and the rounded peristome morph of D. fimbriatus (the latter two known from Pac Kha, northern Vietnam) in shell size and shape, length of R2 and R3, and position of the swelling in R3 ( Páll-Gergely et al. 2017). The specimens from Nan Province, Thailand (Fig. 4D ) differ from the type specimens in having a longer R3, a more shouldered R3 swelling, a stronger descending aperture, and a parieto-columellar angle. Despite those differences, we preliminarily identified the specimens from Nan Province as D. notus . Refer to Discussion regarding the color of living specimen and variation in operculum morphology.

Figures

Figure 4. A, B. Dicharax cucullatus, specimens CUMZ 7422 from Siribhum Waterfall, Doi Inthanon, Chiang Mai Province; A. With operculum; C, D. Dicharax notus C. Syntype NHMUK 1903.7.1.3065; D. Specimen CUMZ 7425 from Tham Luang Sa Koen, Nan Province. Close-up images of the aperture not to scale. Photo: NHM (C.).

Figure 5. Living Dicharax specimens. A. Dicharax cucullatus, specimen CUMZ 7432 from Doi Inthanon, Chiang Mai Province; B. Dicharax notus, specimen CUMZ 7425 from Tham Luang Sa Koen, Nan Province. Both photographed in the laboratory. Not to scale. Photo: A. Pholyotha.

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.