Xenurobrycon

Mendonça, Marina Barreira, Peixoto, Luiz Antônio Wanderley, Dutra, Guilherme Moreira & Netto-Ferreira, André Luiz, 2016, A new miniature of Xenurobryconini (Characiformes: Characidae) from the rio Tapajós basin, Brazil, Neotropical Ichthyology (e 150057) 14 (1), pp. 1-8 : 7

Key to the species of Xenurobrycon

1a. Adipose fin present......... X. pteropus (rio Solimões basin)

1b. Adipose fin absent......................................................... 2

2a. Jaws teeth unicuspid, bicuspid, and tricuspid ................ .......................... X. heterodon (Upper rio Amazonas basin)

2b. Jaws teeth exclusively conical ...................................... 3

3a. Infraorbitals 4 and 5 present ......................................... 4

3b. Infraorbitals 4 and 5 absent .......................................... 5

4a. Anal-fin hooks of mature males larger posteriorly ........ .................................. X. polyancistrus (rio Mamoré basin)

4b. Anal-fin hooks of mature males similar in size or decreasing posteriorly..... X. macropus (rio Paraguai basin)

5a. Posterior half of both caudal-fin lobes darkened; hooks on last unbranched plus 9-12 anal-fin rays; infraorbital 1 present ..................................... X. varii (rio Tapajós basin)

5b. Posterior half of both caudal-fin lobes hyaline; hooks on anal-fin rays only on last unbranched and 4 th- 5th branched rays; infraorbital 1 absent ............................... ................................ X. coracoralinae (rio Araguaia basin)