Gudeodiscus (Gudeodiscus) dautzenbergi (Gude, 1901)

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 : 13

Taxon classification Animalia Stylommatophora Plectopylidae

Gudeodiscus (Gudeodiscus) dautzenbergi (Gude, 1901) Figures 8 E–F, 9 K–L, 14 A–G

Plectopylis Dautzenbergi Gude 1901a, Journal de Conchyliologie, 49: 198-200., Figs 1 a–f. Plate 6, Figs 1 a–c. ["That Khé (le type); entre Cho-Moï et Bac-Kan; entre Bac-Kan et Nac-Ri"]

Plectopylis persimilis Gude 1901a, syn. n., Journal de Conchyliologie, 49: 209-211., Figs 7 a–f, Plate 6, Figs 7 a–c. ["Environs de That-Khé”].

Plectopylis schlumbergeri , - Zilch 1959-1960, Handbuch der Paleozoologie, 6 (2) Euthyneura: Fig. 2094.

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

Types examined.

Tonkin, That-Khé, MNHN 24603 (holotype of dautzenbergi , Figure 8E); Environs de That-Khé, leg. Messager (n. 22.), MNHN 24602 (holotype of persimilis , Figure 8F).

Museum material examined.

Tonkin, Nja-Ba-Thà, coll. Dosch ex Rolle, SMF 341738/1; Tonkin, That-Khé, coll. Dorsch ex Rolle ex Messager, SMF 172083/2; Tonkin, coll. Jetschin ex Bonnet 1900, SMF 102823/1; Fr. Indochina, Tonkin, That Ké, leg. Demange, 1911, HNHM 10278/2; Tonkin, coll. Sayer 1969, MNHN-IM-2012-2273/1; Tonkin, coll. Letellier 1949, MNHN-IM-2012-2274/1; Bac-Kan, leg. Messager 1904, coll. Lavezzari, 1929, MNHN-IM-2012-2290/5; Tonkin, leg. Messager, MNHN-IM-2012-2292/2; Bac-Kan, leg. Messager, MNHN-IM-2012-2297/2; Tonkin, coll. Denis 1946, MNHN-IM-2012-2303/4; Bac-Kan, leg. Messager, MNHN-IM-2012-2314/7; That Khé, leg. Messager, MNHN-IM-2012-2327/4; Bac-Kan, leg. Messager, MNHN-IM-2012-2331/5; Bac-Kan, leg. Messager, MNHN-IM-2012-2437/1; Bac-Kan et That Khé, coll. Staadt 1969, MNHN-IM-2012-2280/2; Na-Ri, leg. Messager, MNHN-IM-2012-2461/1; That-Khé, leg. Messager, MNHN-IM-2012-2373/6; That-Khé, leg. Messager, MNHN-IM-2012-2378/4; Bac-Kan, leg. Messager, MNHN-IM-2012-2382/4; Bac-Kan, leg. Messager, MNHN-IM-2012-2383/4+14jb; Bac-Kan, leg. Messager, MNHN-IM-2012-2402/3; Than-Moi, coll. Staadt, 1969, MNHN-IM-2012-2336/1; Bac-Kan, leg. Messager, MNHN-IM-2012-2337/26+2jb; That-Khé, leg. Messager, MNHN-IM-2012-2354/4; Cao-Bang, leg. Messager, MNHN-IM-2012-2360/1; Tonkin, That-Khé, coll. Salisbury ex Beddome, Tonkin, coll. Lucas, Acc. no. 2351, NHMUK 20130614/2; Tonkin, coll. Lucas, Acc. no. 2351, NHMUK 20130615/1; Tonkin, coll. Trechmann, Acc. no. 2176, NHMUK 20130616/2; Tonkin, That Ke (?), coll. Kennard, A. S. ex auct. (Gude), NHMUK 20130617/1; Tonkin, That-Khe, coll. Rolle, 4/11/08, NHMUK 20130618/2; Tonkin, That-Khé, 13/6/03, NHMUK 20130619/2; Tonkin, That-Khé, NHMUK 1901.7.11.1/1; Tonkin, That-Khé, NHMUK 1920.1.20.18/1; Tonkin, That-Khé, NHMUK 1908.12.21.142-143/2; Tonkin, That-Khé, NHMW 46024/1; Tonkin, That-Khé, coll. Rolle, NHMW 92559/2; Tonkin, That-Khé, coll. Oberwimmer, NHMW 71640/O/10285/1; Tonkin, That-Ke, coll. Wagner ex Messager, NHMW 71640/O/10285/1 (mixed sample with schlumbergeri ); Bac Kan, coll. Steenberg, ZMUC-GAS-1084/1; Tonkin, coll. Steenberg, ZMUC-GAS-1805/2.

New material examined.

Vn10-44 Bắc Kạn Province, Chợ Mới (left bank of river); 21°52.682'N, 105°47.078'E, leg. Hemmen, Ch. & J., 17.03.2010., PGB/3; Vn10-42 Thái Nguyên /Bắc Kạn Province, ca. 1 km S of Chợ Mới; 21°52.707'N, 105°46.172'E, leg. Hemmen, Ch. & J., 17.03.2010., PGB/3; 2011/103 Bắc Kạn Province, Chợ Mới, eastern bank of the river, Khuôn Thung cross 500 m towards Quảng Chu Commune, right side of the road, 21°52.508'N, 105°47.328'E, leg. Hunyadi, A., 21.11.2011., HA/10+4jb, PGB/1; 2011/104 Thái Nguyên Province, Chợ Chu (=Chu Market), rocky wall above the NE part of the village, 90 m, 21°54.613'N, 105°39.195'E, leg. Hunyadi, A., 21.11.2011., HA/3.

Diagnosis.

Shell medium-sized or large, with irregular growth lines, but appearing almost smooth; spire slightly elevated, apertural lip thick but blunt; apertural fold strong and oblique, connected to the callus, but reaching its maximum height some distance from the callus (Figures 9 K–L). Parietal wall with two parietal lamellae; the anterior one has an anteriorly conspicuously elongated lower “leg”; this structure may have resulted from the connection of the anterior lamella and the lower plica; middle palatal plicae oblique (Figures 14 A–G).

Measurements

(in mm): D = 16.7-20.6, H = 8.9-9.8 (n=3, Vn10-42); D = 16.1-17.8, H = 7.9-9.2 (n=2, Vn10-44).

Differential diagnosis.

Gudeodiscus villedaryi , which is probably the closest relative, differs from Gudeodiscus dautzenbergi by the presence of an additional horizontal parietal plica under the vertical lamellae, near the suture. Distinguishing Gudeodiscus dautzenbergi from some similar looking populations of Gudeodiscus villedaryi is impossible without breaking the shell and observing the parietal plicae. Most populations of Gudeodiscus villedaryi however, have a sharp periumbilical keel, which always absent in Gudeodiscus dautzenbergi (see also Remarks under Gudeodiscus villedaryi ). Gudeodiscus dautzenbergi is flatter and more widely umbilicated than Gudeodiscus giardi . The latter species has a domed shell, thinner shell wall and thicker peristome. For comparisons with Halongella schlumbergeri , see under that species. Distinguishing Gudeodiscus dautzenbergi from Halongella schlumbergeri requires experience, but is possible without breaking the shell on the basis of the formation of the peristome and the apertural fold (Figures 9 K–N).

Intraspecific diversity.

Low; shell characters stable.

Distribution

(see Figure 40): This species as well as Plectopylis persimilis (synonym of Gudeodiscus dautzenbergi ) were described from That-Khé (northern Lạng Sơn Province) (see Figure 39). Our newly-collected material is from the border region of the Thái Nguyên and Bắc Kạn provinces.

Remarks.

The holotype of Plectopylis persimilis and that of Plectopylis dautzenbergi do not show significant differences in terms of shell shape, size, aperture shape and the formation of the plicae and lamellae; therefore we synonymise Plectopylis persimilis with Plectopylis dautzenbergi . These two species were described in the same publication ( Gude 1901a), therefore the name introduced earlier ( dautzenbergi , page 198) is considered a senior synonym.

Gudeodiscus dautzenbergi and Gudeodiscus villedaryi are separated here on the basis of the presence or absence of a lower plica, although the two species may be conspecific. More information is necessary to clarify the distinctness of Gudeodiscus dautzenbergi .

The specimen figured by Zilch (1960, Fig. 2094) under the name Plectopylis (Endoplon) schlumbergeri is missing. There is a note written by Zilch saying that he found the box empty on 11.12.1963 (Ronald Janssen, pers. comm., October 2013). Although the specimen could not be examined by us, we are confident in stating that the figure shows a shell of Gudeodiscus dautzenbergi .