Piabarchus is a small genus of characid tetras from central South America, found across Brazil, Argentina, Bolivia, and Paraguay in tributaries of the Paraná-Paraguay system. The atlas covers 2 species, both compact fish running 2 in as adults - a laterally compressed, silvery body, a single soft-rayed dorsal fin, and the small adipose fin typical of the characid family. The genus name echoes 'piaba,' a catch-all term used across Brazil for small silvery characins, and like many of its relatives it likely moves in loose schools over sand and gravel runs in flowing water.
Piabarchus is little known outside ichthyological literature and is not established in the aquarium trade, so its care requirements and behaviour in captivity are not well documented. Conservation data are similarly thin: one of the two species carries a Least Concern IUCN assessment, while the other has not yet been evaluated, which is common for small-bodied, regionally restricted characins that attract little survey effort outside targeted fieldwork.