Gudeodiscus (Gudeodiscus?) hemmeni Pall-Gergely & Hunyadi

Pall-Gergely, Barna, Hunyadi, Andras, Ablett, Jonathan, Lương, Hao Văn, Fred Naggs, & Asami, Takahiro, 2015, Systematics of the family Plectopylidae in Vietnam with additional information on Chinese taxa (Gastropoda, Pulmonata, Stylommatophora), ZooKeys 473, pp. 1-118 : 22

Taxon classification Animalia Stylommatophora Plectopylidae

Gudeodiscus (Gudeodiscus?) hemmeni Pall-Gergely & Hunyadi sp. n. Figures 2 C–D, 9F, 11 G–J

Type material.

2012/61 Sơn La Province, Hà Nội 156 km towards Mộc Châu, left side of the road nr. 6, rocky wall, 1110 m, 20°45.993'N, 104°53.868'E, leg. Hunyadi, A., 06.06.2012., holotype HNHM 97458 (Figure 2C), HA/11 paratypes+4jb (not paratype), PGB/3 paratypes; 2012/62 Sơn La Province, Hà Nội 156 km towards Mộc Châu, right side of the road nr. 6, rocky wall, 1110 m, 20°46.085'N, 104°53.888'E, leg. Hunyadi, A., 06.06.2012., HA/13 paratypes+2jb (not paratypes), PGB/1; Vn12-104 Sơn La Province, right side off road Mộc Châu to Sơn La, 20°52.567'N, 104°35.310'E, leg. Hemmen, Ch., 02.10.2012., HE/1; Vn10-103A Hòa Bình Province, ca. km 156 old road Hà Nội to Sơn La (right side off road), 20°46.000'N, 104°53.885'E, leg. Hemmen, Ch. & J., 15.10.2010., HE/1 (Figure 2D); Vn10-76A Sơn La Province, ca. 32 km from Mộc Châu to Hà Nội (old road), 20°47.351'N, 104°50.063'E, leg. Hemmen, Ch. & J., 02.04.2010., HE/1.

Diagnosis.

Shell small, with slightly elevated spire, characteristically shaped aperture having wide upper sinulus and small apertural fold (Figure 9F); parietal wall with two lamellae and horizontal plicae above and below; palatal plicae depressed Z-shaped; free from each other, or connected to each other with a ridge (Figures 11 G–J).

Description.

Shell very small to small, light brown to chocolate brown, with slightly elevated spire, consists of 5.25-5.5 whorls; suture relatively shallow, especially at the first 3-4 whorls; protoconch (2.25-2.5 whorls) glossy, very finely, regularly ribbed, but the ribs are sometimes hardly visible, they are more prominent at the upper part of the whorls, close to the suture; teleoconch without notable spiral lines, very finely regularly ribbed; sculpture strength equal on ventral and dorsal side; umbilicus narrow and deep; aperture with widened upper part (sinulus), apertural lip whitish, thin, slightly expanded but not reflexed; apertural denticle (fold) always present, very small, free from the callus or connected to it.

Two specimens were opened. Parietal side with a stronger anterior lamella with anteriorly widened lower part, and a slimmer posterior lamella; shorter upper and longer lower horizontal plicae free from the anterior lamella, the lower one a bit extends beyond the anterior lamella in the anterior direction. Palatal side with six plicae; first and last are straight, the others are depressed Z-shaped and are connected with a ridge.

Measurements

(in mm): D = 9.5-10.1, H = 4.3-5.2 (n=5, belonging to different populations).

Differential diagnosis.

Gudeodiscus hemmeni sp. n. differs from most Gudeodiscus phlyarius populations by the smaller shell, shorter denticle (fold) in the aperture, thinner apertural lip, the wider and reflexed apertural rim, the wide upper sinus of the aperture, lack of spiral lines in the sculpture and narrower umbilicus. Gudeodiscus anceyi is usually smaller, has a longer apertural fold, prominent spiral sculpture, a weaker callus and differently shaped aperture.

In all localities, Gudeodiscus hemmeni sp. n. lives sympatrically with Gudeodiscus messageri raheemi ssp. n., which is much larger, lacks the apertural fold, and usually has an anterior lamella which is dissolved into small denticles.

Intraspecific diversity.

Low; shell characters are stable, although only a few shells are known.

Etymology.

The new species is dedicated to Jens Hemmen (1944-2012), malacologist and much-valued friend, who contributed to our revision by providing shell and ethanol-preserved material.

Type locality.

Sơn La Province, Hà Nội 156 km towards Mộc Châu, left side of the road nr. 6, rocky wall, 1110 m, 20°45.993'N, 104°53.868'E.

Distribution

(see Figure 43). The new species is known from few locations in south-eastern Sơn La province.