Autapomorphies of Hyphessobrycon luetkenii:

1. Subtemporal fossa (18): (1> 0) medially extended to middle exoccipital. Paralleled in node 211.

2. Length of laterosensory canal of dentary (79): (0> 1) reduced or absent. Paralleled in node 279 and in Aphyocharax nattereri, Bryconamericus rubropictus, Hyphessobrycon elachys, Nantis cf. indefessus, and Thayeria boehlkei.

3. Number of branched pelvic-fin rays (258): (1> 0) six or less. Paralleled in the Aphyocharacinae, in nodes 220, 236, 280, and 302, and in Axelrodia lindeae, Cheirodon interruptus, Cyanocharax alburnus, Hollandichthys multifasciatus, and Hoplocharax goethei . Some trees: Paralleled in Hasemania nana and Hyphessobrycon elachys .

4. Pelvic-fin bony hooks in adult males of species bearing hooks on fins (309): (1> 0) absent. Paralleled in Creagrutus anary, Hyphessobrycon eques, Phenacogaster tegatus, Pseudocorynopoma doriae, and Stethaprion erythrops . Some trees: Paralleled in Markiana nigripinnis and Psellogrammus kennedyi .

5. Pectoral-fin bony hooks in adult males of species bearing hooks on fins (310): (0> 1) present. Paralleled in node 268 and in Astyanax cf. asuncionensis, A. lineatus, Bario steindachneri, Bryconamericus cf. iheringii, B. rubropictus, Hyphessobrycon socolofi, and Phenacogaster tegatus .

6. Dorsal-fin bony hooks in adult males of species bearing hooks on fins (311): (0> 1) present. Paralleled in nodes 248 and 268 and in Astyanax cf. asuncionensis, A. lineatus, Bario steindachneri, Bryconamericus rubropictus, Hyphessobrycon socolofi, Nematocharax venustus, and Probolodus heterostomus .

7. Caudal-fin bony hooks in adult males of species bearing hooks on fins (312): (0> 1) present. Paralleled in node 268 and in Acrobrycon tarijae, Astyanax cf. asuncionensis, A. lineatus, Bario steindachneri, Hyphessobrycon socolofi, and Probolodus heterostomus .

8. Position of anal-fin bony hooks of adult males (316): (0> 2) asymmetrically disposed and irregularly arranged. Some trees: Paralleled in node 295.