The ghost knifefishes consist of the family Apteronotidae, which are ray-finned fishes in the order Gymnotiformes. These fish are native to Panama and South America. They inhabit a wide range of freshwater habitats, but more than half the species in the family are found deep in rivers (typically deeper than ) where there is little or no light. The genus Apteronotus is "artificial" and some of the species do not actually belong in it; it is polyphyletic. It has been claimed that Apteronotus magdalenensis is up to , These nocturnal fish have small eyes, and some species may exhibit sexual dimorphism in their snout shape and jaws. However, after a number of recent taxonomic advances, Eschmeyer's Catalog of Fishes recognizes 94 species in 16 genera and 2 subfamilies.

  • Subfamily Apteronotinae <small>Jordan, 1923</small>
  • Genus Adontosternarchus <small>Ellis, 1912</small>
  • Genus Apteronotus <small>Lacépède, 1800</small>
  • Genus Compsaraia <small>Albert, 2001</small>
  • Genus Megadontognathus <small>Mago-Leccia, 1994</small>
  • Genus Melanosternarchus <small>Bernt, Crampton, Orfinger & Albert, 2018</small>
  • Genus Parapteronotus <small>Albert, 2001</small>
  • Genus Pariosternarchus <small>Albert & Crampton, 2006</small>
  • Genus Platyurosternarchus <small>Mago-Leccia, 1994</small>
  • Genus Porotergus <small>Ellis, 1912</small>
  • Genus Sternarchella <small>Eigenmann, 1905</small>
  • Genus Sternarchogiton <small>Eigenmann, 1905</small>
  • Genus Sternarchorhynchus <small>Castelnau, 1855</small>
  • Genus Tembeassu <small>Triques, 1998</small>
  • Genus Tenebrosternarchus <small>Bernt, Fronk, Evans & Albert, 2020</small>
  • Subfamily Sternarchorhamphinae <small>Albert, 2001</small>
  • Genus Orthosternarchus <small>Ellis, 1912</small>
  • Genus Sternarchorhamphus <small>Eigenmann, 1905</small>

<gallery class="center" mode="nolines" widths="200" noborder="no" caption="Members of Apteronotidae">

File:Adontosternarchus balaenops.jpg|Adontosternarchus balaenops

File:Apteronotus albifrons.jpg|Apteronotus albifrons

File:Compsaraia samueli.jpg|Compsaraia samueli

File:LatPT2 gray.tif|Melanosternarchus amaru

File:Orthosternarchus tamandua.png|Orthosternarchus tamandua

File:Sternarchorhynchus oxyrhynchus.jpg|Sternarchorhynchus oxyrhynchus

File:Tenebrosternarchus preto.jpg|Tenebrosternarchus preto

</gallery>

The following cladogram is based on a 2019 phylogenetic study analyzing both mitochondrial and nuclear gene sequences of Apteronotidae:

References