Sphoeroides is a genus of pufferfish in family Tetraodontidae that is mostly marine and estuarine across the Atlantic and Pacific coasts of the Americas, but the atlas's 2 species are its South American freshwater-tolerant outliers, recorded from Brazil, Peru, Colombia, Ecuador, Venezuela, Guyana, Suriname, and French Guiana - essentially the Amazon and Guiana-shield river systems. Both share the family's unmistakable body plan: no scales, a fused beak-like set of tooth plates for crushing hard-shelled prey, and the ability to inflate the body with water as a defense against predators. Atlas sizes run 5–11.5 in.
The Amazon puffer (Sphoeroides asellus) and banded puffer (S. psittacus) sit at the freshwater edge of a genus better known from brackish estuaries and coastal flats, and they are far less established in the aquarium trade than the true freshwater puffers of Africa and Asia; care information specific to these two species is sparse. Both carry a Least Concern IUCN status. As with pufferfish generally, caution around handling and any consumption is warranted - many Tetraodontidae carry tetrodotoxin, and species-level toxicity in this pair is not something to assume either way without direct evidence.