Pincerna costulosus ( Bavay & Dautzenberg, 1912 )

Páll-Gergely, Barna, 2023, Revision of the Alycaeidae of China, Laos and Vietnam (Gastropoda: Cyclophoroidea) II: The genera Alycaeus and Pincerna, Zootaxa 5249 (2), pp. 253-276 : 263-266

Pincerna costulosus ( Bavay & Dautzenberg, 1912)

( Figs 8 , 9 )

Alycaeus costulosus Bavay & Dautzenberg, 1912: 49–50 , pl. 4, figs 1–4.

Pincerna costulosa — Páll-Gergely et al., 2017: 10, fig. 3F; Páll-Gergely 2017: 214; Páll-Gergely et al. 2020: 172 .

Pincerna vallis Z.-Y. Chen & M. Wu, 2020: 42, figs 1, 4A, B, 5A. new synonym

Pincerna vallis — Páll-Gergely et al., 2020: 185 .

Type material. VIETNAM: Tonkin , Phong Tho, leg. Messager, MNHN-IM-2000-31786 (syntype, Fig. 8A–D ); Tonkin, Phong Tho, coll. Staadt, 1969, MNHN IM-2012-27043 /2 (probably syntype, Fig. 8E–H ) .

Additional material examined. LAOS: Phongsaly Province, old forest on the northern bank of Nam Leng , 575 m, 21°26.039′N, 102°02.165′E (locality code: 21L05), clay, shale, leg. Abdou, A. & Muratov, I. V ., 15 March 2005, MNHN IM-2012-27217 /1; Phongsaly Province, old forest just north of Nam Leng (river), ca. 6 km NE of Boun Tai, 560 m, 21°25.676′N, 102°00.724′E (locality code: 31L04), clay, shale, leg. Abdou, A., Muratov, I. V ., & Phothihoumphanh , N., 07 December 2004, MNHN IM-2012-27220 /2; Phongsaly Province, old forest and banana plantation SE of Boun Tai , 801 m, 21°22.054′N, 102°00.034′E (locality code: 23L04), clay, shale, leg. Abdou, A. & Muratov, I. V ., 02 December 2004., MNHN IM-2012-27219 /1; Phongsaly Province, NNE of Nam Leng and Nam Bun confluence, 614 m, old forest near ravine, clay, shale, 21°25.925′N, 101°58.869′E (locality code: 27L05), leg. Abdou, A. & Muratov, I. V ., 18 March 2005, MNHN IM-2012-27218 /3 ( Fig. 8I–L ); Phongsaly Province, SW of Phongsaly, near the road to Boun Neua, 1343 m, 21°39.663′N, 102°05.243′E (locality code: 12L05), dry old forest in ravine, clay, shale, leg. Abdou, A. & Muratov, I. V ., 10 March 2005, MNHN IM-2012-27216 /1; Xiangkhoang Province, caverns among boulders at large sinkhole below small settlements (5 houses about 6 km SW of Bank Knong ), 1062 m a.s.l., 19°23.265′N, 102°58.521′E (locality code: JG29 ), leg. Grego, J., 23 February 2017, JG/1 ( Fig. 9A–D ) . VIETNAM: Tonkin, Lao Kay , coll. Letellier, 1949, MNHN IM-2012-27214 / 1 (ex MNHN IM-2012- 27035 , vanbuensis ) ; Lao Kay , leg. Messager no. 26, RBINS/2 (syntype mixed sample with A. vanbuensis ) . CHINA, Hechi Shi, Fengshan Xian, Paoli Xiang , southeastern edge of Paoli , cave, 460 m a.s.l., 24°22.707′N, 107°03.825′E (locality code: 2009/104), leg. Hunyadi, A. 21 October 2009, HA/1 (identification questionable, see remarks) .

Diagnosis. A small to medium-sized alycaeid species with a shell that is slightly higher than wide, R1 strongly, regularly ribbed, R2 extremely short, R3 or normal length, smooth, with low, central swelling.

Description. Shell higher than wide, yellowish or off-white when fresh; protoconch finely granulate, rather matte, consisting of 1.5 or lightly less whorls; R1 glossy, of 2.5 whorls, with regular, rather strong ribs and extremely fine spiral striation; R2 extremely short, consisting of ca. 6 lighter stripes (=breathing tunnels) only; breathing tunnels not or only very slightly elevated from the shell surface; constriction between R2 and R3 rather shallow; R3 or normal length, with low swelling; R3 nearly smooth with some widely-spaced thread-like ribs; aperture rounded; outer peristome strongly expanded and slightly reflected; inner peristome thickened, protruding; boundary between inner and outer peristomes clearly visible; umbilicus entirely or nearly entirely closed by reflected peristome.

Measurements (in mm). D = 3.4–4.8, H = 3.9–4.9 (multiple populations, n = 7).

Operculum: Thefragmentaryoperculumofasinglespecimen(MNHN-IM-2012-27214)wasexamined.Operculum semitransparent, thin, horny, concave, both outer and inner surface multispiral, no nipple found on the inner side.

Variation in specimens. The typical specimens from northernmost Vietnam are slightly larger than the newly collected in northern Laos.

Differential diagnosis. This species is easily recognisable based on the combination of the shell shape (higher than wide), regularly ribbed R1, and very short R2. See also under Pincerna acroptychia n. sp.

Distribution. This species is known from northern Laos (Phongsaly and Xiangkhoang provinces), and the northernmost part of Vietnam (Lai Chau and Lao Kay provinces) ( Fig. 6 ).

Remarks. Some Indian Cycloryx species (e.g. C. graphicus dihingensis (Godwin-Austen, 1914) , C. thompsoni (Godwin-Austen, 1914) , C. burrailensis (Godwin-Austen, 1914)) are so similar to P. costulosus , that it was challenging to find any notable differences by comparison under the microscope. This may indicate that Northern Lao, northern Vietnamese and Chinese Pincerna species belong to the genus Cycloryx .

Pincerna vallis ( Fig. 9E–H ), described from the Chaibuxi National Forest Park, Hubei Province, China, is treated here as a junior synonym of P. costulosus . In its original description, Chen and Wu (2020) mentioned that P. vallis had a ribbed R3, which is smooth in P. costulosus . However, examination of several P. costulosus shells (including syntypes) revealed that P. costulosus shows some variability in this respect. The range of other northern Vietnamese terrestrial operculate species also reach the Chinese Hubei Province, such as Pseudopomatias amoenus Möllendorff, 1885 , P. nitens Páll-Gergely, 2015 , Dicharax cristatus ( Möllendorff, 1886) and Metalycaeus heudei (Bavay & Dautzenberg, 1900) (see Páll-Gergely et al. 2015, 2017).

The single shell collected in the Chinese Guangxi Province ( Fig. 9I–M ) is larger than any other P. costulosus shells (D: 4.8 mm, H: 4.9 mm), and has stronger ribs than any other samples of the same species. It is provisionally identified as P. costulosus , although more material from that area is necessary to understand the diversity of Pincerna in southern China.

Figures

FIGURE 6. Distribution of Pincerna Preston, 1907 species. Circles: Pincerna costulosus (Bavay & Dautzenberg, 1912) (yellow circle indicates the type locality of Pincerna vallis Z.-Y. Chen & M. Wu, 2020); Yellow triangle: Pincerna acroptychia n. sp.; Green rhomb: Pincerna yaanensis Z.-Y. Chen, 2022. The map was made using Google Earth Pro.

FIGURE 8. Shells of Pincerna costulosus (Bavay & Dautzenberg, 1912).A–D: MNHN-IM-2000-31786 (syntype); E–H:Phong Tho, MNHN-IM-2012-27043 (probable syntype); I–L: Northern Laos, MNHN-IM-2012-27218.

FIGURE 9. Shells of Pincerna costulosus(Bavay & Dautzenberg, 1912).A–D: Laos, Phongsaly Province, JG29; E–H:Holotype of Pincerna vallis Z.-Y. Chen & Wu, 2020; I–M: Pincerna cf. costulosus, Guangxi, China, 2009/104. Photos: B. Páll-Gergely (A–D, I–H), taken from the original description (E–H).