Gymnotus, Linnaeus, 1758

Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, Neotropical Ichthyology 16 (2), pp. 1-111 : 56

Gymnotus

1. Body elongated (subcilindrical); light-beige transverse bars narrow and distant from each other along the side of the body.............................................................. G. pantanal

1’. Body deep (knife-shaped); light-beige transverse bars narrow and close to each other along the side of the body ............................................................................................. 2

2. Transversal series above lateral line with 11 or 12 scale rows (to the mid dorsum); two to seven light-beige transverse bars along the side of the body, some of them forming an inverted Y .................................. G. paraguensis

2’. Transversal series above lateral line with 6 to 9 scale rows (to the mid dorsum); light-beige transverse bars along the side of the body not forming Y ........................... 3

3. Head lenght contained 8.3 to 11.1 times in total length; interorbital contained 2.3 to 2.4 times in head length........ .................................................................. G. inaequilabiatus

3’. Head lenght contained 7.1 to 8.2 times in total length; interorbital contained 2.6 to 2.7 times in head length........ ................................................................................ G. sylvius