Dicharax stuparum, Páll-Gergely & Hunyadi, 2018

Páll-Gergely, Barna & Hunyadi, András, 2018, Four new cyclophoroid species from Thailand and Laos (Gastropoda: Caenogastropoda: Alycaeidae, Diplommatinidae, Pupinidae), Zoosystema 40 (3), pp. 59-66 : 62

Dicharax stuparum n. sp.

( Fig. 1F-K )

TYPE MATERIAL. — Thailand. Chiang Rai Province, Doi Tung, 50 m before Wat Phra That Doi Tung , around the car park, 1350 m a.s.l., 20°19.540’N, 99°49.987’E, leg. Hunyadi A., 12.II.2015., HNHM 100178 (holotype, D = 1.87 mm, H = 0.95 mm), coll. HA (2 paratypes) .

ETYMOLOGY. — The specific epithet stuparum (Latin: of the two stupas) refers to the temple of the Mt. Doi Tung, which is known for its twin stupas.

TYPE LOCALITY. — Thailand, Chiang Rai Province, Doi Tung, 50 m before Wat Phra That Doi Tung , around the car park, 1350 m a.s.l., 20°19.540’N, 99°49.987’E.

DIAGNOSIS. — A very small species with smooth R1, short R2 having dense, curved ribs, and a long R3 with a blunt thickening.

DIFFERENTIAL DIAGNOSIS. — Dicharax (?) abdoui, which is known from Laos, has a more rounded shell outline from dorsal view, a more elevated protoconch, a shorter R2 with low riblets, and a less expanded outer peristome. The Vietnamese Dicharax (?) ellipticus also has a shorter R2 without elevated ribs. The Malaysian tiny Dicharax species ( D. canaliculatus , D. microdiscus and D. parvulus ; see photos in Páll-Gergely et al. 2017) all have a regularly ribbed R1. See also under Dicharax caudapiscis n. sp.

DISTRIBUTION. — This species is known from the type locality only.

DESCRIPTION

Shell very small to the genus, off-white, depressed, shell outline oval from standard dorsal view, body whorl rounded; protoconch with 1.5 whorls, glossy; R1 with slightly more than one whorl, also glossy, with fine, irregular growth lines on the dorsal side and relatively strong ribs inside umbilicus; boundary between R1 and R2 clearly visible because R2 bears dense, curved ribs (c. 46-48 altogether); ribs curve posteriorly (= away from aperture) at proximal end of R2, whereas anteriorly (= towards aperture) at anterior part of R2; cross section of ribs and microtunnels could not be examined; R2 and R3 c. 100-110 degrees combined, R3 slightly longer than R2; boundary of R2 and R3 marked with a very slight constriction; R3 glossy, with low swelling; aperture rounded, oblique to shell axis; peristome thickened; outer peristome strongly expanded and reflected, especially in direction of umbilicus; inner peristome protruding; boundary between inner and outer peristomes clearly visible. Operculum and soft anatomy unknown.

Measurements (in mm)

D = 1.8-1.87, H = 0.92-0.95 (n = 2).

REMARKS

See under Dicharax caudapiscis n. sp.

Figures

FIG. 1. — Shells of Dicharax Kobelt & Möllendorff,1900 species:A-E, Dicharax caudapiscis n. sp.(holotype); F-K, Dicharax stuparum n. sp.(holotype).Photograph: Barna Páll-Gergely. Scale bars: A-C, F-H, 1 mm; D, 300 μm; E, K, 100 μm; I, J, 500 μm.