Bakyietaia mutica (Kobelt, 1909), 2025

Bakyietaia mutica (Kobelt, 1909) gen. et comb. nov.

Figs 16–17 View Fig View Fig

Vivipara boettgeri mutica Kobelt, 1909 in Kobelt 1906 –1909: 194, pl. 39 figs 3–4 (“ Hainan ”, Hainan Province, China).

Vivipara boettgeri Kobelt, 1909 in Kobelt 1906 –1909: 137–138, pl. 26 figs 1–7. [non Paludina boettgeri Möllendorff, 1890 , junior homonym].

Viviparus muticus – Yen 1939: 38, pl. 3 figs 18–19.

Sinotaia mutica – Zilch 1955: 77, figs 50–51.

Angulyagra mutica – Liu et al. 1995: 14.

Diagnosis

Shell medium in size (22.14 ± 1.74 mm), conical, whorls inflated, with weak primary keels, prominent keel above suture; columellar lip recurved, forming callus covering umbilicus completely; operculum with small nuclear region (around 1/4 of inner opercular region) with shiny grains or veins; outer marginal tooth of radula with 19 to 24 small sharp cusps.

Material examined

Holotype of Vivipara boettgeri mutica

CHINA • dry preserved spec.; Hainan Province, O.v. Möllendorff leg.; SMF.38817 .

Holotype of Vivipara boettgeri

CHINA • dry preserved spec.; O.v. Möllendorff leg.; SMF.7652 .

Paratypes of Vivipara boettgeri mutica

CHINA • 2 specs (preserved dry); Hainan Island ; SMF.38815 • 3 specs (preserved dry); Hainan Island ; SMF.38816 .

Other material

CHINA – Hainan Province • 3 specs (preserved in ethanol); Haikou, wetlands near Yangshan Reservoir ; 20 Oct. 2019; bought by Sheng-Zhuo Huang on local market; ZMB.122711 • 3 specs (preserved in ethanol); Dingan County, Shuikou Village , 0.5 m deep on wall of cement canal; 6 Mar. 2022; Le-Jia Zhang leg.; ZMB.122724 • 1 spec. (preserved dry); same data as for preceding; YHY-BAKMUT-XC-1 • 2 specs (preserved in ethanol); Haikou City, wetland in Xue Village , 0.1 m deep on rock substrate; 5 Mar. 2022; Le-Jia Zhang leg.; ZMB.122746 • 3 specs (preserved in ethanol); Haikou City, a canal in a farming field near Yangshan Reservoir , 0.1 m deep on rock; 5 Mar. 2022; Le-Jia Zhang leg.; ZMB.122752 • 2 specs (preserved in ethanol); Wenchang City, a pond in Jinjiahu Village , 0.5 m deep on rock; 9 Nov. 2020; Ji-Ze Ruan leg.; ZMB.122772 • 6 specs (preserved dry); same data as for preceding; YHY-BAKMUT-WC-19 , YHY-BAKMUT-WC-36 , YHY-BAKMUT-WC-1 , YHY-BAKMUT-WC-22 , YHY-BAKMUT-WC-37 , YHY-BAKMUT-WC-39 .

Description

Adult shell ( Fig. 16A–K View Fig ) medium in size (22.14 ± 1.74 mm), thin but sturdy, conical, olive to dark olive brown, with five to six whorls, apex acute; teleoconch whorls inflated, sometimes with shoulder, with three weak, smooth primary keels, with one to two even 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 two to four weak keels, all keels usually darker than rest of shell surface; aperture ovate, less than half of shell height, inner shell surface bluish white, outer lip thin, always with an obvious angular periphery, columellar lip covered with thick inner shell layers, always white, adult columellar lip recurved, sometimes forming a relatively wide crescent-shaped callus, this structure or columellar lip completely covering umbilicus.

Operculum ( Fig. 16L–M View Fig ) corneous, ovate, relatively thin, dark orange to red; exterior surface smooth; interior surface with small nuclear region, around 1/4 of inner opercular region, with shiny grains or veins or smooth glossy surface.

Radular ( Fig. 17 View Fig ) (n = 3) central tooth with one broad central denticle and four to five small sharp cusps on either side; lateral tooth with one broad central denticle and four to 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 width as lateral tooth, with 19 to 24 small sharp cusps.

Remarks

The newly collected specimens from Haikou City of Hainan have a shell that is very similar to that of the holotype. Bakyietaia mutica is one of the species of Bakyietaia gen. nov. with weak primary keels. It can be easily distinguished from most congeners based on its medium-sized thin conical shell with three very weak primary keels. It is morphologically similar to Bakyietaia fontinalis gen. et sp. nov. and Bakyietaia naiadica gen. et sp. nov. However, it can be distinguished from B. fontinalis based on the inflated whorls (vs non-inflated whorls in B. fontinalis ) and fewer cusps on the outer marginal teeth (19–24 vs 26–29); it can be distinguished from B. naiadica based on its more conical shell with prominent keel above suture. The distribution of Bakyietaia mutica does not overlap with those of B. fontinalis and B. naiadica . The recommended Chinese name is 钝Ḇṉ田ª.

Habitat and distribution

Rock substrate in the shallow water of rivers and lakes in northern Hainan Province, China.