Gudeodiscus (Gudeodiscus?) cyrtochilus (Gude, 1909)

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 : 10-13

Taxon classification Animalia Stylommatophora Plectopylidae

Gudeodiscus (Gudeodiscus?) cyrtochilus (Gude, 1909) Figures 2F, 15 E–G

Plectopylis cyrtochila Gude 1909, Proceedings of the Malacological Society of London, 8: 217-218., Plate 9, Figs 5, 5 a–b. [ “Muong-Kong”].

Gudeodiscus cyrtochilus , - Páll-Gergely & Hunyadi 2013, Archiv für Molluskenkunde, 142 (1): 11-12., Figs 17, 41, 75 (map).

Types examined.

Tonkin, Muong-Kong, leg. Messager, NHMUK 1922.8.29.59 (syntype, Figure 2F).

Museum material examined.

Muong-Kong, coll. Denis 1946, MNHN-IM-2012-2249/3; Muong-Kong, leg. Messager, MNHN-IM-2012-2251/14.

New material examined.

2012/46 Hà Giang Province, Hà Giang 105.2 km towards Ðồng Văn, Vân Chải Commune, right side of the road nr. 4C, 23°08.865'N, 105°10.789'E, leg. Hunyadi, A., 31.05.2012., HA/7+4 jb; 2012/47 Hà Giang Province, Hà Giang 105.5 km towards Ðồng Văn, Vân Chải Commune, left side of the road 4C, 23°09.084'N, 105°10.774'E, leg. Hunyadi, A., 31.05.2012., HA/19+10jb, PGB/3; 2012/49 Hà Giang Province, Hà Giang 149.4 km towards Mèo Vạc, about 5 km SE from Ðồng Văn, right side of the road 4C, ca 1090 m, 23°15.528'N, 105°22.545'E, leg. Hunyadi, A., 01.06.2012., HA/9, PGB/1; 2012/50 Hà Giang Province, Ðồng Văn 7.5 km towards Mèo Vạc, left side of the road nr. 4C, 1260 m, 23°14.981'N, 105°23.657'E, leg. Hunyadi, A., 01.06.2012., HA/6jb; Vn11-141 Hà Giang Province, km 105.5 on road 4c, between Yên Minh and Đồng Văn (NE of Hà Giang town), 23°08.996'N, 105°10.332'E, leg. Hemmen, Ch. & J., 21.03.2011., HE/16; Vn11-144 Hà Giang Province, km 149.4 on road 4c, between Đồng Văn to Mèo Vạc (NE of Hà Giang Town), 23°15.507'N, 105°22.564'E, leg. Hemmen, Ch. & J., 23.03.2011., HE/4; Vn11-145 Hà Giang Province, km 153 on road 4c, between Đồng Văn to Mèo Vạc (NE of Hà Giang Town), left side of road, 23°14.738'N, 105°23.786'E, leg. Hemmen, Ch. & J., 23.03.2011., HE/1; Vn11-123A Hà Giang Province, ca. 7.5 km from Đồng Văn to Mèo Vạc (right side off road), 23°14.906'N, 105°23.445'E, leg. Hemmen, Ch. & J., 23.03.2011., HE/3.

Diagnosis.

Shell very small to small, discoid, polished with very weak apertural rim, weak or missing callus and without apertural fold. Parietal wall with two lamellae and an upper and a lower horizontal plica; the plicae can be free from the anterior lamella or in contact with it; palatal plicae straight, parallel, horizontal, sometimes connected with a slight ridge (Figures 15 E–G).

Measurements

(in mm): D = 8.9-9.9, H = 4.8-5.0 (n=4, MNHN-IM-2012-2251); D = 10.2-11.1, H = 5.3-5.6 (n=3, 2012/47); D = 10.2-11.2, H = 4.8-5.4. (Chinese specimens, n=4, see Páll-Gergely and Hunyadi 2013).

Differential diagnosis.

The Chinese Gudeodiscus yunnanensis has a similar shell shape but possesses only one vertical parietal lamella (the anterior one is absent). The two species can be separated only the basis of the presence or absence of the anterior lamella. In Gudeodiscus soosi and in most specimens of Gudeodiscus multispira , few denticles are present between the upper and lower plicae, at the place of the anterior lamella. Moreover, Gudeodiscus multispira has a greater number of whorls and the last whorl is wider in relation to the previous one than in Gudeodiscus cyrtochilus . Gudeodiscus infralevis is larger with a more elevated spire, stronger apertural lip and usually a weak apertural fold. See also under Gudeodiscus fischeri .

Intraspecific diversity.

Low; shell characters rather stable. The parietal plicae and lamellae and their respective position (reaching each other or not) show some diversity within the species. The palatal plicae are not variable, but in some shells they are connected to each other with a ridge, whereas in others they are free. It is possible that mature specimens tend to have a connection between the plicae. The species is easily recognisable and can be separated from other plectopylid species without major problems.

Distribution

(see Figure 41): The species was described from “Muong-Kong” (=Mường Khương, Lào Cai Province; see Figure 39). Material is noted from northeast of this locality, from northern Hà Giang Province and eastern parts of Yunnan Province (China) (see Páll-Gergely and Hunyadi 2013).

Remarks.

The drawing in the original description of Gudeodiscus cyrtochilus is incomplete (the posterior lamella was omitted).

Some fresh shells have a characteristic mosaic structure on the dorsal surface (yellowish and darker reddish areas are following each other). This coloration is known in some " Chersaecia " ( munipurensis Godwin-Austen, 1875, oglei Godwin-Austen, 1879, serica Godwin-Austen, 1875) and Plectopylis (e.g. anguina Gould, 1847, bensoni Gude, 1914, karenorum W. Blanford, 1865) species.