Table 2.

Comparative analysis of the genera Indochinella Bolotov, Pfeiffer, Vikhrev & Konopleva gen. nov., Oxynaia Haas, 1911, and Nodularia Conrad, 1853 on the basis of conchological features.

Conchological features	Unio pugio Benson, 1862, the type species of the genus Indochinella	Unio jourdyi Morlet, 1886, the type species of the genus Oxynaia*	Unio douglasiae Griffith & Pidgeon, 1833, the type species of the genus Nodularia**
Shell shape	Cuneiform	Somewhat cuneiform, with more height, anteriorly rounded, posteriorly elongated and pointed	Oval-form, slightly narrow in the posterior part
Umbo	Not pronounced	Very pronounced, elevated	Very pronounced, elevated
Umbo sculpture	V-shaped	Nodulose wrinkles	Nodulose wrinkles
Umbo position	In the first third of the shell	In the first half of the shell	In the first half of the shell
Pseudocardinal teeth of the left valve	Two separated ribbed teeth placed in parallel line with one another	Anterior tooth rectangular and sharp, posterior tooth thick and pyramidal	Anterior rectangular, sharp and ribbed, posterior tooth small and pyramidal
Pseudocardinal teeth of the right valve	Anterior tooth reduced, posterior tooth somewhat pyramidal and wrinkled	Anterior tooth lamella-shaped, posterior tooth rectangular, wrinkled	Anterior tooth reduced, lamella-shaped, posterior tooth somewhat trapeziform and ribbed
Lateral teeth	Rather short, two teeth on the left and one tooth on the right valve	Long, two teeth on the left and one tooth on the right valve	Straight, elongate, sharp with small scratches, two teeth on the left and one tooth on the right valve

*Based on the two syntypes (MNHN-IM-2000-33685, Coll. du Journal de Conchyliologie, ex Coll. Morlet; type locality: Tonkin. Environs de Dang-son (Jourdy) [p. 77]¹⁸; Bac-Hat, étangs du bord de la rivière Claire (Jourdy) [p. 290]¹⁸. **Based on a sample from Soldatskoe Lake, Razdolnaya River Basin, Russian Far East (RMBH no. biv_227_12).