Bakyietaia subcostata (Gray, 1833), 2025

Bakyietaia subcostata (Gray, 1833) gen. et comb. nov.

Figs 7–8 View Fig View Fig

Paludina subcostata Gray, 1833 in Griffith & Pidgeon 1833 –1834: 599, pl. 36 fig. 3 (“ China ”).

Paludomus futaii Gredler, 1889: 159 (“Peho, Kuang-tung ”, refers to Bei River, Guangdong Province, China). Syn. nov.

Sinotaia? futaii – Zilch 1974: 64, pl. 7 fig. 9.

Angulyagra subcostata – Liu et al. 1995: 14.

Diagnosis

Adult shell medium to large (27.17 ± 3.64 mm), rounded and thin, primary keels weak, teleoconch with weak primary keels; columellar lip recurved, forming callus covering umbilicus completely; operculum with small nuclear region (around 1/5 of inner opercular region) with shiny grains or veins; outer marginal tooth of radula with 29 to 43 small sharp cusps.

Material examined

Holotype of Paludina subcostata

CHINA • dry preserved specimen; NHMUK.2007.01.7.1 .

Holotype of Paludomus futaii

CHINA • dry preserved specimen; Guangdong Province, Bei River ; GFBI.22 .

Other material

CHINA – Guangdong Province • 4 specs (preserved in ethanol); Guangzhou City, Zhengguo Town, Zeng River , 0.7 m deep under rock; 25 Sep. 2019; Da-Ming Shi leg.; ZMB.122694 • 3 specs (preserved dry); Guangzhou City, Zhengguo Town, Zeng River , 0.7 m deep under rock; 25 Sep. 2019; Da-Ming Shi leg.; YHY-BAKSUB-ZG-1 , YHY-BAKSUB-ZG-18 , YHY-BAKSUB-ZG-28 • 3 specs (preserved dry); Zhaoqing City, Xiaoxiang Town, Xi River , under rock; Aug. 2021; Ji-Lin Jiang leg.; KIZ.240084 • 2 specs (preserved in ethanol); Qingyuan City, Shitan Town, Bin River , 0.6 m deep on rock; 24 Sep. 2022; Mr Chen leg.; ZMB.122767 • 2 specs (preserved dry); Qingyuan City, Shitan Town, Bin River , 0.6 m deep on rock; 24 Sep. 2022; Mr Chen leg.; YHY-BAKSUB-ST-1 , YHY-BAKSUB-ST-4 • 2 specs (preserved in ethanol); Zhaoqing City, Huaiji County, Sui River ; 15 Sep. 2022; ZMB.122766 • 1 spec. (preserved in ethanol); Qingyuan City, Jintan Town, Bin River ; 10 Oct. 2022; KIZ.240085 • 4 specs (preserved in ethanol); Zhaoqing City, Fengkai County, Xi River ; 19 Jan. 2024; Lejia Zhang leg.; KIZ.240086 .

Description

Adult shell ( Fig. 9A–Q View Fig ) medium to large (27.17 ± 3.64 mm), thin but sturdy, rounded, olive to dark brown; with five to six whorls, apex acute; teleoconch whorls inflated, sometimes forming shoulder, with three smooth weak primary keels, with one to two weaker smooth secondary keels located between suture and first keel, sometimes one additional weak keel located between first and second/second and third keels, base of shell with three to five weak keels; aperture ovate, large, around half of shell in height, inner shell surface bluish white to purple, outer lip thin, always with a relatively rounded periphery, columellar lip covered with thick inner shell layers, always whitish orange or pink, adult columellar lip recurved, forming a very narrow crescent-shaped callus or without this structure, columellar lip or this structure completely covering umbilicus.

Operculum ( Fig. 9R–S View Fig ) corneous, ovate, thin, yellow; exterior surface smooth; interior surface with nuclear region small, around 1/5 of inner opercular region, with shiny grains or veins.

Radular ( Fig. 10 View Fig ) (n = 4) central tooth with one broad central denticle and five to six 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 four small sharp cusps on either side; outer marginal tooth wide, almost same as lateral tooth in width, with 29 to 43 small sharp cusps.

Remarks

Bakyietaia subcostata can be easily distinguished from most congeners based on the rounded thin shell with weak primary keels. It can be differentiated from the morphologically similar species Bakyietaia chenghuang gen. et sp. nov. based on the larger number of small cusps on the outer marginal teeth of the radula (29–43 vs 15–16). Paludomus futaii was described based on a juvenile shell of this species, and it is here placed in synonymy of B. subcostata . The recommended Chinese name is 次Oiṉ田ª.

Habitat and distribution

Rock substrate in the shallow water of rivers of Guangdong Province, China.