Pincerna acroptychia, Páll-Gergely, 2023

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 : 260

Pincerna acroptychia n. sp.

( Fig. 5A–E )

Type material. Holotype: VIETNAM: Ha Giang Province, km 105.5 km on road no. 4c, between Yen Minh and Dong Van (NE of Ha Giang Town ), 23°08.996′N, 105°10.332′E (locality code: Vn 11-141), leg. Ch. & J. Hemmen, 21 March 2011 ( SMF 370401 , Fig. 5A–E ).

Diagnosis. A medium-sized Pincerna species with a shell that is slightly higher than wide, R1 and R3 with elevated, sharp, lamella-like ribs (6 on R3), R2 short, with ca. 16 densely arranged, low ribs, R3 with blunt, elongated central swelling.

Description. The single available shell is white, although it is slightly corroded, the original colour may also be white; shell ca. as high as wide; protoconch smooth, consisting of 1.5 whorls; R1 consists of 2.25 whorls, with elevated, sharp, lamella-like ribs, rib density very slightly decreases from beginning of teleoconch towards its end, on the last quarter whorl spaces between ribs abruptly increase; R2 and R3 less than 90 degrees combined, R2 very short, consisting of ca. 16 densely arranged, low ribs (cross sectional view not examined); change between R1 and R2 abrupt due to radical change in rib density; constriction between R2 and R3 deep; R3 with blunt, elongated central swelling and 6 elevated, sharp, lamella-like ribs (similar in density to that at the end of R1); aperture large, rounded; boundary between inner and outer peristomes conspicuous; outer peristome expanded (widest in direction of umbilicus), not reflected; inner peristome slightly protruding; umbilicus open, very narrow, visible only in ventral view, in apertural view covered by reflected outer peristome.

Operculum. Unknown.

Measurements (in mm). D = 4.3, H = 4.4 (holotype).

Differential diagnosis. Pincerna costulosus ( Bavay & Dautzenberg, 1912) is similar in overall shell shape, but that species has lower, less sharp ribs, and its R3 is smooth or ornamented by a few, low ribs. Pincerna maolanensis ( Luo, Zhang & Zhuo, 2009) has similar rib density and its R3 is also strongly ribbed, but its R2 is much longer than that of the new species. This new species also differs from P. yaanensis by the strongly elevated R3 ribs, and moreover, the R3 swelling of the new species is central, whereas it is shifted towards the aperture in the Chinese species.

Etymology. The specific epithet acroptychia (to be used as a noun in apposition) refers to the fact that several species of the Madagascan endemic genus Acroptychia Crosse & P. Fischer, 1877 has a series of elevated ribs on the last whorl, similar to this new Pincerna species.

Distribution. Pincerna acroptychia n. sp. is known only from the type locality ( Fig. 6 ).

Figures

FIGURE 5. Shells of Pincerna Preston, 1907 species.A–E: Pincerna acroptychia n. sp. (holotype); F–I: Pincerna maolanensis (Luo, Zhang & Zhuo, 2009) (holotype); J–M: Pincerna yaanensis Z.-G. Chen, 2022, holotype; N–R: P. yaanensis, locality 2015/53, coll. HA. Photos: Kaibaryer Meng (F–I), B. Páll-Gergely (A–E, N–R), photos from the original description (J–M). White lines indicate length of suture.

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.