The identity of the freshwater crab Aiyunamon tumidum (Wood-Mason, 1871) (Brachyura, Potamidae), with description of a new species from China

Abstract The identity of the freshwater crab, Aiyunamon tumidum (Wood-Mason, 1871), is clarified after the types are re-examined. The type series is mixed and includes specimens of two species. A syntype from Ponsee in Yunnan, P.R. China, is designated the lectotype of the species; those from Hotha in Yunnan are now referred to A. daiae (Zhang & Sun, in Zhang, Pan, Hao & Sun, 2020). Specimens which have previously been referred to as “ A. tumidum ” from other parts of Yunnan are here identified as a new species, Aiyunamon fatum sp. nov.. Aiyunamon fatum is most easily distinguished from congeners by the structure of the male first gonopod.