Key to the species of subgenus Gymnotus (Tigrinus)

1A: band pairs replaced by large, irregular dark brown blotches over entire body … G. (T.) onca

1B: band pairs present … 2

2A: pale interbands rarely extend above lateral line on anterior 50% of body (except in upper Madeira populations) … G. (T.) coropinae

2B: pale interbands extend vertically past lateral line and meet at middorsum … 3

3A: 11 unpaired, straight dark bands, roughly equal in width to pale interbands … G. (T.) melanopleura

3B: 13–24 dark band pairs, greater in width than pale interbands … 4

4A: pale interbands wider dorsally on anterior 50% of body, up to 50% width of dark band pairs (vs. 25% in ventral portion of same band) … G. (T.) coatesi

4B: margins of bands roughly parallel … 5

5A: narrow pale interbands (25% width of dark band pairs) anteriorly and 5–8 partially divided, often H-shaped dark band pairs posteriorly … G. (T.) javari

5B: color pattern occasionally variable, but always consisting of narrow pale interbands (~25% width of dark band pairs) over entire body, dark band pairs infrequently partially divided and never H-shaped … 6

6A: 15–17 dark band pairs; endemic to the Amazon basin … G. (T.) jonasi

6B: 18–23 dark band pairs; endemic to the Orinoco basin … G. (T.) stenoleucus

Phylogenetic revision of Gymnotidae (Teleostei: Gymnotiformes), with descriptions of six subgenera
Jack M. Craig , Lesley Y. Kim, Victor A. Tagliacollo, James S. Albert
Published: November 7, 2019 https://doi.org/10.1371/journal.pone.0224599