Autapomorphies of Knodus breviceps:

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 Coptobrycon bilineatus .

Some trees:

2. Contact between frontals anteriorly to frontal fontanel (21): (0> 1) present. (k9-11). Reversal of synapomorphy 4 of node 206. Paralleled in Bario steindachneri, Exodon paradoxus, Galeocharax humeralis, Hyphessobrycon pulchripinnis, and Odontostoechus lethostigmus .

3. Position of ventral margin of posttemporal (252): (1> 0) anterior to lateral margin of epioccipital. (k12-14). Paralleled in nodes 162, 285, and 301 and in Aulixidens eugeniae, Creagrutus anary, Diapoma speculiferum, Moenkhausia cf. intermedia, and Pyrrhulina australis . Some trees: Paralleled in node 247.

4. Scales covering caudal-fin lobes (328): (0> 1) covering onethird of their length. (k9-11). Paralleled in node 222 and in Aulixidens eugeniae, Distichodus maculatus, Markiana nigripinnis, and Nematocharax venustus .