Myleus

Myleus is a genus of serrasalmids from South America, where found in the Amazon, Orinoco and São Francisco basins, as well as river basin of the Guiana Shield. They are found in rivers with moderately or fast-flowing water, including rapids. They are primarily herbivores, but also take some animal matter. Depending on the exact species, they reach up to 12–42 cm (0.4–1.4 ft) in standard length, and the adult males have a double-lobed anal fin and filamentous extensions...