Gasteropelecus is one of the classic hatchetfish genera, family Gasteropelecidae, instantly recognizable for the deep, keeled chest that houses an oversized set of pectoral muscles. The atlas' 3 species - the silver hatchetfish (G. levis), spotted hatchetfish (G. maculatus) and common hatchetfish (G. sternicla) - range across the Amazon, Orinoco and other river systems of Brazil, Colombia, Ecuador, Peru, French Guiana, Guyana, Panama and Paraguay, living near the surface of slow, often blackwater forest streams.
That keeled chest lets hatchetfish do something almost no other freshwater fish can: burst clear of the water and glide, pectoral fins whirring, for a stretch of the surface to escape predators - a genuine adaptation, not just a swimming style. In the aquarium, all three species are long-established, peaceful schooling fish for the top of a softwater, densely planted tank, best kept in tightly lidded aquariums (they will jump) and fed small floating foods. Sizes run from about 1.5–3 in, and conservation status is reassuring - two species Least Concern, one not yet evaluated.