Dicharax (?) Kobelt & Mollendorff 1900
- Dataset
- Nineteen new species of Alycaeidae from Myanmar and Thailand (Gastropoda: Caenogastropoda: Cyclophoroidea)
- Rank
- GENUS
- 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
description
Description. Shell off-white, although both available shells were somewhat eroded; shell outline slightly oval in dorsal view; spire slightly elevated, low conical, body whorl with conspicuous peripheral keel; protoconch somewhat elevated, finely granular, spiral striation lacking, 1.75 whorls; R 1 of 1.5 whorls, first half whorl practically smooth, gradually changing to widely, regularly-spaced, strong ribs (ca. 30 ribs on last half whorl of R 1), present on entire R 1 except area between peripheral keel and outer edge of periumbilical keel, which has fine spiral striation; some spiral striation visible on dorsum of R 1, and between ribs; boundary between R 1 and R 2 distinct due to dense R 2 ribs; R 2 ribs curved toward aperture, ca. 34 – 36 R 2 ribs present; spaces between R 2 ribs narrower than ribs; R 2 + R 3 more than quarter whorl (ca. 110 ˚); R 2 considerably shorter than R 3, slightly more half its length; boundary between R 2 and R 3 distinct due to change in sculpture and deep constriction; R 3 with rounded, elongated swelling situated closer to constriction than to peristome; aperture strongly oblique to shell axis, rounded with basal incision; boundary between inner and outer peristomes not conspicuous; inner peristome strong, somewhat protruding, expanded, basal and palatal portions strongly fringed, outer peristome weaker, expanded, but reflected only in direction of umbilicus; umbilicus funnel-shaped, relatively narrow, less than one third of shell width. Measurements. D: 2.9 – 3 mm, H: 1.9 mm Operculum. Unknown.
description
Figs 14 – 15
diagnosis
Diagnosis. A medium-sized Dicharax species with strong peripheral keel, strongly ribbed and spirally striated R 1, and strongly fringed aperture.
diagnosis
Differential diagnosis. The angled body whorl, the funnel-shaped umbilicus, the flattened dorsal side, and the strongly convex R 3 swelling distinguish this new species from the most similar D. fimbriatus (Bavay & Dautzenberg, 1912), which is known from Laos and Vietnam (Páll-Gergely et al. 2017). The R 1 ribs of this species are stronger than those of most D. fimbriatus populations, and the new species has a spirally striated R 1.
discussion
Remarks. Similarly to some populations of D. omissus (Godwin-Austen, 1914), this species also possesses spiral striation on R 1, which is very rare in Dicharax. Spiral striation on the teleoconch is characteristic for Chamalycaeus, but this species is classified in Dicharax due to the curved R 2 ribs characterizing that genus and its overall shell shape. Possible homology of the spiral striation of these few Dicharax species and other alycaeid genera needs further investigation.
distribution
Distribution. This new species is known only from the type locality (Fig. 17).
etymology
Etymology. The specific epithet admirandus (Latin for astonishing, remarkable, extraordinary) refers to several notable shell characters of this new species, namely the strong keel, strongly fringed aperture, and the spiral striation.
materials_examined
Dicharax sylheticus (Godwin-Austen, 1914) (Examined material: S. Sylhet Hills, W. Channel leg., NHMUK 1903.7.1.55, holotype, Fig. 16) is similar, but has a more elevated spire, a less keeled body whorl, a longer R 2 with less dense ribs, and a rounded aperture.
materials_examined
Material examined. Holotype: Thailand, Loei Province, 9.2 km NW Loei, Buddhist temple, up and N of main cave entrance, 17 ° 35 ’ N, 101 ° 44 ’ E, 250 m a. s. l., 28 Apr. 1988, K. Auffenberg leg., base of cliff under Georissa zone, UF 345861 (D: 2.9 mm, H: 1.9 mm). Paratype: 1 shell, same data as holotype, UF 551218.