Myleus is a genus of silver dollars in family Serrasalmidae, the same family that holds the piranhas and pacus, from river basins across tropical South America - the atlas's countries span Brazil, Guyana, Suriname, Colombia, French Guiana, Peru, and Venezuela. Atlas species run 5–15 in and share the classic silver-dollar body plan: a deep, laterally compressed, disc-shaped body built for maneuvering through flooded forest and open water alike. Unlike their piranha relatives, Myleus species are predominantly herbivorous and omnivorous, grazing on fallen fruit, seeds, plant matter, and some invertebrates rather than hunting fish.
Several Myleus species are genuinely popular in the aquarium trade under the silver dollar name, prized for their calm schooling behavior and shimmering flanks - M. setiger, the sailfin red hook silver dollar, is especially sought after for its striking red-and-black hooked anal fin, and the blue-tinted M. micans (pacu azul) is another trade staple. They are large, active fish that need a big planted-safe or hardscape tank and a mostly vegetable-based diet as adults. Conservation status is mixed rather than alarming across the six atlas species, with Data Deficient and Not Evaluated results outnumbering confirmed Least Concern, reflecting how little targeted assessment silver dollars have received relative to their popularity.