Gudeodiscus (Gudeodiscus?) suprafilaris (Gude, 1908)

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 : 37-40

Taxon classification Animalia Stylommatophora Plectopylidae

Gudeodiscus (Gudeodiscus?) suprafilaris (Gude, 1908) Figures 9 A–B, 9R, 14 S–Y

Plectopylis suprafilaris , - Gude 1908, Journal de Conchyliologie, 55: 353-355., Figs 4 a–e, Plate 7, Figs 7-9. ["Quang Huyen"].

Gudeodiscus suprafilaris , - Páll-Gergely & Hunyadi 2013, Archiv für Molluskenkunde, 142 (1): 8.

Types examined.

Tonkin, Quang-Huyen, leg. Mansuy, MNHN 24586 (holotype?, Figure 9A).

Museum material examined.

Nga-Son, leg. Messager, MNHN-IM-2012-2234/2; Nga-Son, leg. Messager, MNHN-IM-2012-2254/3.

New material examined.

Vn10-125 Cao Bằng Province, ca 60 km from Cao Bằng to Bảo Lạc (right side off road), 22°39.494'N, 105°51.059'E, leg. Hemmen, Ch. & J., 19.10.2010., PGB/1; 2011/70 Lạng Sơn Province, Lạng Sơn, NNE edge of Vọng Phu Mountain, 21°51.183'N, 106°44.950'E, leg. Hunyadi, A., 11.11.2011., HA/1jb; 2011/81 Cao Bằng Province, Đèo Mã Phục (pass) 500 m towards Quảng Uyên, left side of the road, rock cavern, 610 m, 22°43.981'N, 106°20.333'E, leg. Hunyadi, A., 14.11.2011., HA/73+10jb, PGB/3 (see Figure 9B); 2011/85 Cao Bằng Province, Cao Bằng 34.5 km towards Đông Khê, left side of the road, 500 m, 22°27.487'N, 106°25.047'E, leg. Hunyadi, A., 15.11.2011., HA/4jb; 2012/44 Cao Bằng Province, southern edge of Pắc Rảo, Trùng Khánh 3 km towards Quảng Uyên, left side of the road, 570 m, 22°48.961'N, 106°30.533'E, leg. Hunyadi, A., 28.05.2012., HA/1; Vn10-67 Cao Bằng Province, right off old rd. 4A, ca 29 km from Cao Bằng to Đông Khê, 22°28.737'N, 106°21.767'E, leg. Hemmen, Ch. & J., 26.03.2010., HE/2.

Diagnosis.

Shell small, discoid-globular, with weak apertural lip and usually a small denticle in the aperture (Figure 9R). The sudden change of the shell sculpture (reticulated above, smooth below) is very characteristic of this species. For the morphology of the plicae see Remarks and Figures 14 S–Y.

Measurements

(in mm). D = 13.1, D = 7.3 (n=1, Vn10-125); D = 11.1-12.1, H = 6.2-6.3 (n=3, 2011/81); D = 12-14.1, H = 6.2-7.2 (n=2, Vn10-67).

Differential diagnosis.

The shell shape of Gudeodiscus suprafilaris is similar to that of Gudeodiscus infralevis , but Gudeodiscus suprafilaris has more regular whorls, a more elevated spire and its sculpture changes suddenly from reticulated dorsally to smooth basally on the last whorl. The sudden change of the sculpture and the almost globular shell distinguishes the species from other species ( Gudeodiscus eroessi , Gudeodiscus multispira , Gudeodiscus soosi , Gudeodiscus yunnanensis , Gudeodiscus cyrtochilus and Gudeodiscus fischeri ). The Chinese Gudeodiscus eroessi hemisculptus Páll-Gergely & Hunyadi, 2013 and Gudeodiscus yanghaoi which have similar sculpture are larger, have a flatter shell and different lamellation.

Intraspecific diversity.

The species is very variable in terms of spire height, the formation of parietal and palatal plicae and lamellae, and the extent of the sculptured portion on the dorsal side of the shell. The distinctive aperture shape, minute apertural fold and the unique sculpture render this species distinctive and easy to identify. See also Remarks and Table 10.

Distribution

(see Figure 41). Examined material was from only Cao Bằng and Lạng Sơn Provinces. The type locality (Quang-Huyen) lies in Cao Bằng Province (see Figure 39).

Remarks.

The palatal and parietal plicae and lamellae exhibit extreme variability between populations. The holotype exhibits relatively long, horizontal palatal plicae connected with a ridge; the parietal side possesses a well-developed posterior lamella, upper and lower plica, and a reduced, short anterior lamella (Figures 14 S–T). The museum specimens we examined (probably from the same sample as the holotype) had similar palatal plicae and also a reduced anterior lamella. Two examples collected close to the type locality (2011/81, see Figures 14 U–V and 2012/44) were examined. Shells belonging to both populations had identical palatal plicae to those of the holotype, but in contrast, had a much longer anterior lamella, free from the lower plica or almost united to it. Additionally, in the type series, the sculptured dorsal surface changes to a smooth surface at around the middle line of the body whorl. In contrast, in the two newly-collected samples the change between the two different sculptures occurs lower, closer to the umbilicus.

In a shell from another population (Vn10-125, see Figures 14 X–Y) the palatal plicae were greatly reduced in length so that when viewed through the semi-transparent shell, they appear as though only a single vertical plica was present. The parietal wall of the same shell was ornamented by a strong anterior lamella entirely fused with the lower plica; the posterior lamella was absent, its position was indicated only by a very slight elevation within the structure of the shell.