Two new genera and two new species of freshwater crab (Crustacea, Brachyura, Potamidae, Potamiscinae) from southern Vietnam

Recent surveys in south Vietnam found two new genera and two new species of Potamidae: Angiangmon nuicoto gen. et sp. nov . and Lamdongmon tanhlinhensis gen. et sp. nov . Angiangmon gen. nov . is characterised by, its relatively flat, almost smooth dorsal carapace surface; a serrated anterolateral margin; the third maxilliped ischium is short; the flagellum of exopod of third maxilliped exopod is very short and flap-like, or highly reduced to vestigial the ambulatory legs are relatively long and slender; the male first gonopod terminal article is short with the distal part of the terminal article curved inwards, and the male second gonopod is longer than the first gonopod. Lamdongmon gen. nov . is unique in the male first gonopod being prominently sinuous, as well as a suite of characteristics such as subquadrate carapace of the epibranchial tooth is indistinct; the merus of the third maxilliped is subquadrate; the flagellum of the exopod of the third maxilliped is well developed; and the ambulatory legs are covered with dense setae.