Tongchuania H. Chen, H. - Q. Xiang, Y. - M. He, X. - C Huang & X. - P. Wu 2025, gen. nov.

GenusTongchuaniaH. Chen, H.-Q. Xiang, Y.-M. He, X.-C Huang & X.-P. Wu gen. nov. Type species. Tongchuania mingiana H. Chen, H.-Q. Xiang, Y.-M. He, X.-C Huang & X.-P. Wu, gen. et sp. nov. (Fig. 4). Diagnosis. Shell medium-sized, thick, solid, glossy, yellowish-brown, overall slender shape; anterior margin slightly indented, ventral margin nearly straight, dorsal margin straightened; periostracum with straight blackish-green rays; umbo sculptured with W-shape ridges. Both left and right valves with two pseudocardinal teeth. Nacre white. Description. Shell medium-sized, thick, solid, glossy, yellowish-brown, overall slender shape; anterior margin regularly rounded and slightly indented, ventral margin nearly straight, dorsal margin straightened; periostracum with straight blackish-green rays; umbo located at 1 / 3 of shell length and obviously higher than the dorsal margin; umbo sculptured with W-shape ridges. Ligament long, narrow. Anterior adductor muscle attachment elliptical; posterior adductor muscle attachment round and smooth. Both left and right valves with two pseudocardinal teeth. Left valve with two pseudocardinal teeth, anterior tooth wide, posterior tooth slightly thick and acute triangle, and having two lateral teeth. Right valve with two thick elevated pyramidal pseudocardinal teeth and one lateral tooth. Nacre white, and shiny (Fig. 4). Within the incurrent aperture, there are not obvious papillae arranged in one row, with brown pigmentation; papillae of the excurrent aperture well developed, stubby, and arranged in one row, with brown pigmentation. The inner gills are larger than the outer gills. Labial palps are thin and small, without pigmentation (Fig. 5 A, B). Etymology. The name of the genus originates from the ancient Chinese name for Dazhou. Vernacular name. 通川蚌 (tong chuan bang) (Chinese); Tongchuan mussel (English). Remarks. The species of this genus is similar only to those in the genus Nodularia within the Tribe Unionini, but it can be easily distinguished by its periostracum with straight blackish-green rays and the right valve with two thick, elevated pyramidal pseudocardinal teeth.