Guiunio Dai, Chen, Li & Wu 2025, gen. nov.

GenusGuiunioDai, Chen, Li & Wu gen. nov. Type species. Guiunio rarus Chen, Li, Dai & Wu, sp. nov. Diagnosis. Shell medium-sized, moderately thick, flat, long, sub-glossy, opaque. Anterior small, rounded and short; posterior extremely expanded, wide and long, with an indistinct obtuse angle in the middle of posterior margin. Umbo inflated, slightly higher at the hinge line, located at 1 / 4 of the dorsal margin, with concentric square carving. Periostracum yellowish green to brown with thin growth lines. Papillae on flap margin highly degraded. Description. Shell medium-sized, moderately thick, flat, long, sub-glossy, opaque. Anterior small, rounded and short; posterior extremely expanded, wide and long, with an indistinct obtuse angle in the middle of posterior margin. Dorsal margin slightly curved downwards and truncated in behind; ventral margin weakly curved or retuse. Umbo inflated, slightly higher the hinge line, located at 1 / 4 of the dorsal margin, with concentric square carving. Periostracum yellowish green to brown with thin growth lines. Posterior slope with an indistinct low secondary posterior ridge end in the angle on the posterior margin. Growth lines arranged in irregular concentric circles. Hinge long. Ligament short and strong. Beak cavities shallow, open. Mantle attachment scars on the pallial line obvious. Anterior adductor muscle scars irregularly oval, deep, smooth; posterior adductor muscle scars long oval, smooth. Left valve with two pseudocardinal teeth, posterior tooth elevated pyramidal or degenerated; anterior tooth thick and pyramidal. Right valve also with one pseudocardinal tooth, low triangular. Lateral teeth of both valves long and thin. Nacre light orange to white. Mantle light brown, aperture margins black, papillae on flap margin highly degraded. Gills light brown, inner gills slightly longer and wider than outer gills. Labial palpsrown, distally pointed and irregularly fan-shaped in appearance. Visceral mass grayish white, foot light orange. Etymology. The species is made from the Gui for the abbreviation for Guangxi and unio for the unionid type genus. Vernacular name. 桂蚌属 (gùi bàng shǔ).