Guiunio rarus Chen, Li, Dai & Wu 2025, sp. nov.

Guiunio rarus Chen, Li, Dai & Wu sp. nov. Fig. 2 Type material. Holotype • 25_NCU_XPWU_GR001, Zhongduhe River [中渡河], Luzhai County [鹿寨县], Liuzhou City [柳州市], Guangxi Zhuang Autonomous Region [广西壮族自治区], China, 24.60754 ° N, 109.80318 ° E, leg. Fan Li, January 2024. Paratypes • n = 2, 25_NCU_XPWU_GR002 –003, other information same as holotype. Diagnosis. Same as the genus. Description. Same as the genus. Measurements. Holotype: shell length 50.0 mm, height 29.4 mm, width 14.2 mm. Paratypes: shell length 32.2–72.3 mm, height 18.1–42.2 mm, width 7.8–26.2 mm. Etymology. The species is named after Latin rarus for rare, referring to the rarity of it. Vernacular name. 稀有桂蚌 (xī yǒu gùi bàng). Distribution and ecology. Known from the type locality only (Fig. 3). Living in the slow flowing stream with muddy and sandy bottom alongside Cristaria plicata (Leach, 1814), Nodularia douglasiae (Gray, 1833) and Lanceolaria gladiola (Heude, 1877). In addition, the new species was associated with a yet-to-be-described species of Rhodeus Agassiz, 1832, which may be laying eggs in the gills of it (all type specimens of the new species were collected during the dry season in winter, so no fish eggs were observed in the gills). It is an occasional species in the type locality, accounting for less than 1 / 20 of the population of all freshwater mussels.