Autapomorphies of Coptobrycon bilineatus:

1. Anterior convergence of ventral diverging lamellae with nasal septum of mesethmoid (31): (1> 0) absent, or confluent near anterior end of nasal septum. Paralleled in Aulixidens eugeniae and Knodus breviceps .

2. Nasal (33): (0> 1) absent.Paralleledin Hyphessobryconelachys.

3. Maxillary teeth (134): (1> 0) absent. Paralleled in Aulixidens eugeniae, Iguanodectes geisleri, Parecbasis cyclolepis, and Stichonodon insignis . Some trees: Paralleled in Hyphessobrycon elachys and Psellogrammus kennedyi .

4. Number of maxillary teeth (135): (1> 0) only one, or absent. Paralleled in the Astyanax clade, in nodes 284 and 290, and in Aulixidens eugeniae, Cheirodon interruptus, Hyphessobrycon bifasciatus, and Iguanodectes geisleri . Some trees: Paralleled in Hasemania nana, Paracheirodon axelrodi, and Parecbasis cyclolepis .

5. Number of branched-rays on dorsal-fin (270): (1> 0) eight or fewer. Paralleled in the Stevardiinae and in Hoplocharax goethei, and Piabucus melanostomus .

6. Number of rays on last anal pterygiophore (291): (0> 1) one. Paralleled in Hasemania nana .

7. Horizontal line of chromatophores just dorsal to anal-fin base (344): (0> 1) present. Paralleled in the Heterocharacinae .