Sternopygus

Sternopygus is a genus of glass knifefishes found in tropical and subtropical South America (south to the Río de la Plata Basin), and Panama. They inhabit a wide range of freshwater habitats, from fast-flowing rivers to essentially static waters in floodplains, and shallow habitats to the bottom of deep rivers. S. macrurus will even visit brackish mangrove to feed.

They are medium to large knifefish, with a maximum total length of 23–140 cm (0.8–4.6 ft) depending on the exact species. They feed on invertebrates, small fish and fruits. Most members of Gymnotiformes are nocturnal, but Sternopygus are both nocturnal and diurnal.