Sternopygus
Sternopygus is a genus of glass knifefishes found in tropical and subtropical South America, and Panama. It is the only extant extant member of the subfamily Sternopyginae, with the related fossil genus Humboldtichthys also known from Bolivia.
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 mangroves to feed.
They are medium to large knifefish, with a maximum total length of 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.