Pincerna vanbuensis Preston 1907
Creators: name: Páll-Gergely, Barna
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Architaenioglossa
Alycaeidae
Pincerna

description: Pincerna (?) vanbuensis (Bavay & Dautzenberg, 1900)
(Figs 3H–I, 12, 14G)
Alycaeus (Dioryx) vanbuensis Bavay & Dautzenberg, 1900a: 119–120.
Alycaeus (Dioryx) vanbuensis — Bavay & Dautzenberg, 1900b: 455–456, pl. 11, figs 19–21.
Dioryx vanbuensis — Kobelt, 1902: 340; Varga, 1972: 136, figs 24–25.
Alycaeus vanbuensis —Páll-Gergely et al., 2017: 10, fig. 3C.
Pincerna (?) vanbuensis — Páll-Gergely et al., 2020: 184.
Pincerna clausus D. S. Do & T. S. Nguyen, 2022: 372, figs. 1, 4A–C, 5A–F, 6D; Tables 1, 2. new synonym
Type material. VIETNAM: Tonkin, Van-Bu, leg. Dr. R. Bavay, MNHN-IM-2000-31798 (syntype, Fig. 12A–D).
Additional material examined. CHINA: Guangxi (ŨOE), Hechi Shi (OiṀm), Tiane Xian (Ƒẃǥ), Qimu Xiang, cross towards Lahaoyan (ṄṞṱ), 600 m, 24°51.130′N, 107°11.670′E (locality code: 2013/8B), leg. A. Hunyadi & M. Szekeres, 12 September 2013, HA/10; Guangxi (ŨOE), Tiane Xian (Ƒẃǥ), Qimu Xiang (LJR Ø), Douloulieshita (Maeẉ± DZ), 602 m, 24°51.114′N, 107°11.666′E (locality code: 20111021A), leg. Ishibe, T., Ohara, K., Okubo, K. & Otani, J.U., 21 October 2011, OK/2; Guangxi (ŨOE), Tiane Xian (Ƒẃǥ), Kaimu Xiang (ƜRØ), Lahaoyan (ṄṞṱ), 685 m, 24°50.993′N, 107°09.963′E (locality code: 20111021B), leg. Ishibe, T., Ohara, K., Okubo, K. & Otani, J.U., 21 October 2011, OK/2 (Fig. 12M–P). LAOS: Luang Prabang Province, 19.5 km north of Nong Khiaw, north of Muang Ngoi Neua, vicinity of Tham Panay, 405 m, 20°42.903′N, 102°40.549′E (locality code: 2019/116), leg. A. Hunyadi, 6 October 2019, HA/2; Luang Namtha Province, 43.8 km southwest from centre of Luang Namtha, towards Vieng Phou Kha, Phou Lan, 100 m from the left side of the road, 770 m a.s.l., 20°44.529′N, 101°11.101′E (locality code: 2019/123), leg. A. Hunyadi, 8 October 2019, HA/8; Khammuan Province, Nhommalath, bridge on road no. 12, 43.4 km towards Nongchan, southern edge of Ban Khamhé, right side of the road, 210 m a.s.l., 17°34.743′N, 105°27.515′E (locality code: 2019/108), leg. A. Hunyadi, 30 September 2019, HA/1 (small shell size and ribbing is similar to A. vanbuensis, ‘simple’ peristome reminiscent of A. mouhoti, although the shell may not be fully adult); Luang Prabang Province, 8 km south from centre of Luang Prabang, Tad Thong, environment of the waterfall, 445 m a.s.l., 19°50.145′N, 102°7.939′E (locality code: 2019/112), leg. A. Hunyadi, 4 October 2019, HA/1. VIETNAM: Nat Son, leg. Messager, RBINS /2; Lao Kay, leg. Messager no. 26, RBINS /2 (mixed sample with P. costulosus); Phong Tho, leg Messager, no. 32, RBINS /1; SƠn La Province, Mộc Châu 5 km towards SƠn La, right side of the road no. 6, 755 m, 20°52.551′N, 104°35.318′E (locality code: 2012/60), leg. Hunyadi, A., 06 June 2012, HA/5; SƠn La Province, 17.7 km northwest from centre of SƠn La towards Thuận Châu, Bon Phặng, left side of the road, 755 m a.s.l., 21°21.974′N, 103°47.440′E (locality code: 2020/14), leg. Hunyadi, A., 07 February 2020, HA/2 (Fig. 3H, I); SƠn La Province, Yên Châu District, Lóng Phiêng, 40 km from centre of Mộc Châu towards Pa Lao, left side of the road, 760 m a.s.l., 20°54.683′N, 104°24.040′E (locality code: 2020/22), leg. Hunyadi, A., 09 February 2020, HA/7; SƠn La Province, Mộc Châu Disctrict, Nȏng trường Mộc Châu, Ngũ Động Bản Ȏn, 895 m a.s.l., 20°52.489′N, 104°42.533′E (locality code: 2020/23), leg. Hunyadi, A., 10 February 2020, HA/2; SƠn La Province, 24 km northwest from centre of SƠn La, towards Thuận Châu, Chiễng Pấc, left side of the road, 565 m a.s.l., 21°24.707′N, 103°45.794′E (locality code: 2020/13), leg. Hunyadi, A., 07 February 2020, HA/1; SƠn La Province, Quỳnh Nhai District, 20 km north from junction towards Thuận Châu, Chiễng Khoang, cave above the village, 315 m a.s.l., 21°33.441′N, 103°40.909′E (locality code: 2020/9), leg. Hunyadi, A., 07 February 2020, HA/1; SƠn La Province, Mộc Châu Disctrict, Vân Hồ, northwestern edge of Pa Cốp towards Bó Nhàng, 980 m, 20°46.001′N, 104°45.203′E (locality code: 2020/24), leg. Hunyadi, A., 10 February 2020, HA/5; SƠn La Province, right side off road Mộc Châu to SƠn La, 20°52.567′N, 104°35.310′E (locality code: Vn11-104), leg. Hemmen, Ch., 14 October 2011, HE/17 (Fig. 12I–L), Same data, 02.10.2012., HE/3; Tonkin, Phong Tho, Coll. Staadt, 1969, MNHN IM- 2012-27215/2 (ex MNHN IM- 2012-27043, costulosus, Fig. 12Q–U, 14G); Tonkin, Lao Kay, coll. Letellier, 1949, MNHN IM- 2012-27035/1.
Diagnosis. A small to medium sized species with regularly ribbed R1, smooth and long R2, R3 with blunt swelling, clearly separate inner and outer peristomes and a protruding inner peristome.
Description. Shell yellowish-corneous or off-white when fresh, slightly wider than high; protoconch smooth, consisting of ca. 2 whorls; R1 of ca. 2 whorls, with widely-spaced, thread-like, regular ribs (strongest near the suture) and extremely fine spiral striation; R2 and R3 approx. 110 degrees combined, R2 slightly shorter than R3; constriction between R2 and R3 relatively shallow; R2 without elevated ribs; the whole surface smooth with slender light and thicker darker stripes alternating; cross-sectional view not examined; R3 usually with 1–5 widely-spaced, thread-like ribs; aperture rounded; outer peristome expanded and slightly reflected; inner peristome protruding, thickened; boundary between inner and outer peristomes clearly visible; umbilicus open but narrow, partly of entirely covered by reflected outer lip.
Operculum. The inner and outer surfaces of the operculum of a single specimen (2012/60) was examined (Fig. 3H–I). Operculum calcareous, slightly concave, inner surface somewhat corroded, but no elevated nipple is discernible; outer surface white, glossy, not multispiral.
Measurements (in mm). D = 3.8–5.5, H = 3.8–5.1 (shells from multiple populations, n = 20).
Variation in specimens. The examined samples show variability in terms of shell size, density and strength of R1 ribs. The umbilicus can be closed in those populations in which the body whorl is relatively narrow.
Differential diagnosis. Alycaeus vanbuensis is most similar to A. mouhoti, but differs from that species on the basis of the smaller shell, stronger R1 ribs, and overall thicker peristome. In most cases the boundary between inner and outer peristomes is more clearly visible and the inner peristome is protruding in A. vanbuensis than in A. mouhoti, although there are exceptions (similar traits are rarely visible in A. mouhoti).
Distribution. The type locality (Van Bu is situated in Son La Province, northwestern Vietnam). Additional historical samples are known from Phong Tho (Lai Chau Province), and Lao Kai Province. New localities are reported here from northern Guangxi (China) (Fig. 13).
Remarks. Do and Nguyen (2022) described Pincerna clausa from Điện Biên Province, Vietnam. According to them, that species has a closed umbilicus, while it is open in the most similar species, P. vanbuensis. Furthermore, it has a stronger spiral striation on R1, a weaker ribbing on R2, compared to P. vanbuensis. Here I treat P. clausa (correctly would be clausus as Pincerna is masculine) as a junior synonym of P. vanbuensis because of the following reasons: It is true that most P. vanbuensis populations have an open umbilicus and it is closed in P. clausus, however, a closed umbilicus is rarely found in other populations of P. vanbuensis when the body whorl is narrow (Fig. 12Q–U). Therefore, this character is considered as part of intraspecific variability. While the holotype of P. clausus (Fig. 12E–H) indeed possesses stronger spiral striation than most P. vanbuensis shells, at least one of the figured paratypes (fig. 4B in Do & Nguyen 2022) has weak spiral striation on R1. This suggests that the strength of spiral striation is variable within populations. It is not true that P. clausus has stronger R2 ribs than P. vanbuensis, because those of P. vanbuensis do not elevate from the surface of R2. Instead, they from a smooth R2 area. Overall, P. clausus seems to fit the morphological variability of P. vanbuensis. Moreover, it is known from a single site within the area of that species, therefore there is no strong reason to maintain it as an independent species.
The P. vanbuensis localities mentioned by Do and Nguyen (2022) in the material examined and the localities plotted on the map (fig 1. therein) do not match completely. Here I plotted the sites (Fig. 13) mentioned in that paper.
description: Published as part of Páll-Gergely, Barna, 2023, Revision of the Alycaeidae of China, Laos and Vietnam (Gastropoda: Cyclophoroidea) II: The genera Alycaeus and Pincerna, pp. 253-276 in Zootaxa 5249 (2) on pages 269-272, DOI: 10.11646/zootaxa.5249.2.4, http://zenodo.org/record/7687418