Bakyietaia polyzonata ( Frauenfeld, 1862 ), 2025

Bakyietaia polyzonata ( Frauenfeld, 1862) gen. et comb. nov.

Figs 7–8 View Fig View Fig

Vivipara polyzonata Frauenfeld, 1862: 1165–1166 View in CoL ( type locality not stated in the original description).

Paludina polyzonata View in CoL – Fischer & Dautzenberg 1904: 92. — Dautzenberg & Fischer 1908: 199.

Angulyagra polyzonata View in CoL – Thanh et al. 2004: 3–4, fig. 4. — Richter 2015: 127–128, fig. 3.5.

Angulyagra boettgeri View in CoL – Madsen & Hung 2014: 109, fig. 2 (10 right) [non Paludina boettgeri Möllendorff, 1890 View in CoL ].

Diagnosis

Shell medium (26.60 ± 1.91 mm), thin and conical, whorls inflated, primary keels smooth, moderate keel above suture, outer lip rounded; columellar lip recurved, umbilicus completely or partly calloused; operculum with small nuclear region (around 1/4 of inner opercular region) with shiny grains or veins.

Material examined

Lectotype

CHINA? • dry preserved specimen; designated by Yen (1939); NHMW68037 View Materials .

Paralectotype

CHINA? • 1 spec. (preserved dry); NHMW68038 View Materials .

Other material

CHINA • 3 specs (preserved in ethanol); Guangxi, Chongzuo City, Longzhou County, Shuikou Town , Poliu Village , outlet of an underground river in a cave; 4 Mar. 2023; KIZ.240051 to KIZ.240053.

VIETNAM • 11 specs (preserved in ethanol); Ninh Binh, Reservoir near Dang , Cuc Phuong N.P. ; ZMB.114132 • 1 spec. (preserved in ethanol); Hoa Binh, Tan Lac district, Ngoc Ly ; ZMB.114150 • 3 specs (preserved in ethanol); Bac Kan, Phu Luong, Yen Ninh , Dong Dang ; ZMB.114171 .

Description

Adult shell ( Fig. 7A–J View Fig ) medium in size (26.60 ± 1.91 mm), thin but sturdy, conical, olive to greenish brown, with five to six whorls, apex acute; teleoconch whorls slightly inflated especially on body whorl. Shoulder angular, with three smooth primary keels and one to two weaker smooth secondary keels between suture and first keel. Sometimes, one additional weak keel located between first and second/ second and third keels. Shell base with three to five weak keels, and usually darker than other parts of shell surface; aperture ovate, less than half of shell in height, inner shell surface bluish white, outer lip thin, smooth and rounded. Inner layers of adult columellar lip thickened, white or orange, recurved columellar lip partially or wholly covering umbilicus, sometimes forming a callus.

Operculum ( Fig. 7J–K View Fig ) corneous, ovate, thin, yellow to orange; exterior surface smooth; interior surface with smal nuclear region (around 1/4 of inner opercular region), with shiny grains or veins.

Radular ( Fig. 8 View Fig ) (n = 4) central tooth with one broad central denticle and five small sharp cusps on either side; lateral tooth with one broad central denticle and five small sharp cusps on either side; inner marginal tooth narrow, about half of lateral tooth in width, with one broad central denticle and five to six small sharp cusps on either side; outer marginal tooth wide, almost same as lateral tooth in width, with 21 to 26 small sharp cusps.

Remarks

The newly collected specimens from Longzhou, China have a shell that is very similar to that of the lectotype. The type locality of this species was not clear from the original description, and it was considered simply as China ( Yen 1939). Bakyietaia polyzonata can be distinguished from most congeners, especially Bakyietaia indrapura gen. et sp. nov., by its medium-sized, thin conical shell with inflated whorls, more rounded outer lip and distribution. The recommended Chinese name is 多棱ṉ田ª.

Habitat and distribution

Rivers and lakes of Western Guangxi of China and Northern Vietnam.