Myloplus is a genus of pacus in the family Serrasalmidae — the same family that contains the piranhas, though Myloplus species are herbivorous and omnivorous grazers rather than predators. The atlas's 14 species range from about 6–23 in and are found across the river systems of northern South America, with records from Brazil, Peru, Venezuela, Colombia, Guyana, Suriname, Ecuador, and French Guiana. Like other serrasalmids, Myloplus have a deep, laterally compressed, disc-shaped body, and many species use strong jaws and molar-like teeth to crack seeds, fruit, and nuts that fall into the water from the flooded forest canopy — an important seed-dispersal role in Amazonian and Guianan river ecosystems.
Several Myloplus species reach the aquarium trade under the general 'silver dollar' name, including Myloplus lobatus and the popular Myloplus rubripinnis, the red hook silver dollar, valued for its silver body and vivid orange-red anal fin; these are large, active, mostly peaceful schooling fish that need substantial tank space and plenty of plant matter in the diet as they mature. Others, like Myloplus schomburgkii (the disk tetra) and Myloplus torquatus (the orangefin pacu), are less commonly kept but recognizable within the same silver-dollar body plan. The IUCN tally — five species Least Concern against one Vulnerable, one Near Threatened, and seven still Not Evaluated — suggests a genus that looks reasonably secure where assessed, but with a large share of species still awaiting a formal status.