Autapomorphies of Attonitus ephimeros:

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

2. Rhinosphenoid (47): (1> 0) absent.Reversal of synapomorphy 2 of the Characidae . Paralleled in nodes 207, 260, 280, and 298 and in Aphyocharax nattereri, Bryconamericus scleroparius, Brycon orbignyanus, Hollandichthys multifasciatus, Pseudocorynopoma doriae, and Salminus brasiliensis .

3. Position of opening on neurocranium communicating with laterosensory canal of sixth infraorbital (77): (0> 1) in frontal. Paralleled in nodes 193 and 249 and in Micralestes stormsi .

4. Ventral margin of horizontal process of anguloarticular (109): (1> 0) posteroventrally angled relative to laterosensory canal of dentary from medial view. Reversal of synapomorphy 1 of node 199. Paralleled in nodes 195, 280, and 298.

5. Form of anterior portion of ectopterygoid (157): (0> 1) slender and articulating only to lateral margin of palatine, and lacking ligaments to neurocranium. Paralleled in the Alestidae, in node 170, and in Agoniates anchovia .

6. Bony lamellae between second and third basibranchials (184): (1> 0) absent. Paralleled in the Serrasalmidae and in Axelrodia lindeae, Hollandichthys multifasciatus, Hoplocharax goethei, Jupiaba scologaster, Piabucus melanostomus, Pyrrhulina australis, Rhaphiodon vulpinus, and Xenagoniates bondi .

7. Posterior margin of cleithrum (235): (0> 1) with markedly concave margin, almost forming straight angle. Paralleled in nodes 162, 247, and 253 and in Agoniates anchovia, Characidium borellii, Iguanodectes geisleri, Moenkhausia cf. intermedia, Prionobrama paraguayensis, and Xenagoniates bondi .

8. Number of branched anal-fin rays (287): (1> 0) 17 or less. Reversal of synapomorphy 6 of the Characoidea . Paralleled in the Alestidae, in nodes 280 and 290, and in Prodontocharax melanotus . Some trees: Paralleled in Hasemania nana .

9. Longitudinal position of insertion of adductor mandibulae tendon on dentary (330): (1> 0) on vertical through posterior half of Meckelian cartilage. Reversal of synapomorphy 1 of node 241. Paralleled in nodes 237 and 298.

Some trees:

10. Rows of gill rakers on first ceratobranchial (192): (0> 1) two. (k12-14). Reversal of synapomorphy 3 of node 179. Paralleled in the Iguanodectinae, in node 280, and in Brycon orbignyanus, Bryconaethiops macrops, Carlana eigenmanni, Cheirodon interruptus, Hoplocharax goethei, Hyphessobrycon elachys, Odontostilbe microcephala, Parecbasis cyclolepis, Prodontocharax melanotus, and Rhaphiodon vulpinus . Some trees: Paralleled in node 249.