Autapomorphies of Acestrorhynchus pantaneiro:

1. Position of sphenotic spine relative to hyomandibula (11): (0> 1) displaced anteriorly relative to anterior margin of hyomandibula. Paralleled in nodes 162 and 211 and in Piabina argentea, Salminus brasiliensis, and Serrasalmus maculatus .

2. Position of sphenotic spine relative to the orbit (12): (0> 1) distinctly posterior to orbital margin. Paralleled in nodes 193 and 299 and in Attonitus ephimeros, Cynopotamus argenteus, and Gymnocharacinus bergii .

3. Anterior region of laterosensory canal of frontal (83): (0> 1) opens into a chamber limited. dorsally by frontal and ventrally by lateral ethmoid.

4. Ectopterygoid teeth row (159): (0> 1) present. Paralleled in nodes 168 and 300 and in Distichodus maculatus, Hoplias cf. malabaricus, Serrasalmus maculatus, and Xenagoniates bondi .

5. Rows of gill rakers on third and fourth ceratobranchials (194): (1> 0) one.

6. Total number of transitional vertebrae (228): (0> 1) three or fewer. Paralleled in node 205 and in Characidium rachovii, Cyphocharax spilotus, Micralestes stormsi, and Triportheus pantanensis .

7. Number of branched anal-fin rays (288): (1> 0) 24 or less. Reversal of synapomorphy 5 of the Characidae . Paralleled in nodes 200, 277, and 300 and in Iguanodectes geisleri .

8. Humeral spot (341): (0> 1) horizontally-ovate. Paralleled in node 259 and in Brycon orbignyanus, Jupiaba mucronata, and Roeboides microlepis .

Some trees:

9. Length of medial bony ridge of opercle (170): (1> 0) 60% or greater than opercular length. (k11-14). Paralleled in the Serrasalmidae, in node 210, and in Astyanax abramis, Creagrutus cf. taphorni, Hoplias cf. malabaricus, and Roeboides microlepis . Some trees: Paralleled in Salminus brasiliensis .