Dicharax cyclostoma Pall-Gergely 2021
- Dataset
- Nineteen new species of Alycaeidae from Myanmar and Thailand (Gastropoda: Caenogastropoda: Cyclophoroidea)
- Rank
- SPECIES
- Published in
- Páll-Gergely, Barna, Hunyadi, András, Grego, Jozef, Reischütz, Alexander, Auffenberg, Kurt (2021): Nineteen new species of Alycaeidae from Myanmar and Thailand (Gastropoda: Caenogastropoda: Cyclophoroidea). Zootaxa 4973 (1): 1-61, DOI: 10.11646/zootaxa.4973.1.1
Classification
- kingdom
- Animalia
- phylum
- Mollusca
- class
- Gastropoda
- order
- Architaenioglossa
- family
- Cyclophoridae
- genus
- Dicharax
- species
- Dicharax cyclostoma
description
Description. Shell white, some specimens with very faint brownish or yellowish colouration; shell outline rounded or very slightly oval in dorsal view, shell depressed, spire only slightly elevated, body whorl rounded; protoconch low, glossy, 1.25 – 1.5 whorls; R 1 of 1.25 – 1.75 whorls, glossy without sculptural elements; boundary between R 1 and R 2 conspicuous due to R 2 ribs; R 2 with ribs curved towards aperture, ca. 24 – 26 ribs present; spaces between R 2 ribs narrower than ribs; R 2 + R 3 less than quarter whorl (ca. 80 ˚); R 2 half or less length of R 3; R 3 glossy, smooth; boundary between R 2 and R 3 distinct due to change in sculpture and moderately deep constriction; middle of R 3 with rounded swelling; aperture strongly oblique to shell axis, round; boundary between inner and outer peristomes not conspicuous; inner peristome somewhat protruding, rather slim, outer peristome multi-layered, thickened and expanded, particularly toward umbilicus, but not reflected; umbilicus wide, slightly more than a third of shell width. Measurements. D: 2.22 – 2.68 mm, H: 1.31 – 1.56 mm. Operculum. Unknown.
description
Fig. 19
diagnosis
Diagnosis. A small, depressed Dicharax species with glossy R 1, protruding inner peristome, and round aperture; R 2 + R 3 shorter than a quarter whorl, R 2 half as long as R 3.
diagnosis
Differential diagnosis. Dicharax politus (W. T. Blanford, 1865) (examined material: Phungdo, Arakan, coll. Blanford, NHMUK 1906.4.4.178, 3 probable syntypes, Fig. 20 C) is larger, has a more elevated spire, and longer R 3. Dicharax (?) immaculatus Páll-Gergely, 2017 from Gansu Province, China is similar with low spire and smooth R 1, but with shorter R 2 without elevated ribs, and its peristome much thinner than that of new species. Some populations of D. cristatus (Möllendorff, 1886) possess a smooth R 1 and a low spire, but it has a longer R 2, and is always larger than the new species (Páll-Gergely et al. 2017).
distribution
Distribution. This new species is known only from the type locality (Fig. 5).
etymology
Etymology. This species is named for the very round aperture (Greek cyclo-, ring and stoma, mouth, opening, noun in apposition).
materials_examined
Material examined. Holotype: Thailand, Nakhon Ratchasima Province, 3.4 km W of Ban Mu Si, limestone hill, 14 ° 32.016 ’ N, 101 ° 22.783 ’ E, 380 m a. s. l., 5 May 1987, F. G. Thompson leg., UF 346812 (D: 2.54 mm, H: 1.54 mm). Paratypes: 18 shells, same data as holotype, UF 551219. Other material: 2 juvenile shells, same data as holotype, UF 551220.