Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Craniata Linnaeus, 1758 see Subphylum Vertebrata Cuvier, 1812
     Pisces
       Class Actinopterygii Woodward, 1891 - ray-finned fishes
         Order Gymnotiformes Rafinesque, 1810 - American knifefishes
           1 Family Sternopygidae - glass knifefishes
           2 Family Apteronotidae - ghost knifefishes
           3 Family Rhamphichthyidae - sand knifefishes
           4 Family Hypopomidae
           5 Family Gymnotidae Rafinesque, 1815 - nakedback knifefishes