Potamorhina is a genus of small-mouthed, detritus-feeding characins in the family Curimatidae, native to major river basins of tropical and subtropical South America. The atlas covers 5 species ranging from roughly 9–10.5 in, with records spanning Brazil, Colombia, Peru, Argentina, Venezuela, Ecuador, Paraguay, and Uruguay, a distribution covering the Amazon, Orinoco, and La Plata systems. Curimatids like Potamorhina have deep, laterally compressed, silvery bodies, small toothless or nearly toothless mouths, and long, coiled intestines adapted to processing large volumes of mud and organic sediment, feeding by sifting fine detritus and algae from the substrate rather than hunting or grazing plants directly.
Potamorhina species are not aquarium fish in any meaningful sense; their importance is almost entirely as food fish. Potamorhina altamazonica (llambina) and its relatives form dense, schooling populations that undertake seasonal migrations between river channels and flooded forest or floodplain habitat, and iliophagous, mud-sifting characins like this genus support significant subsistence and commercial fisheries across the Amazon and Orinoco basins. With two of the five atlas species rated Least Concern and three not yet evaluated, the genus is not currently flagged as threatened, though as heavily fished, migratory floodplain fish, their population trends are tied closely to river connectivity and flood-pulse dynamics.