Autapomorphies of Thayeria obliqua:

1. Form of anterior expansion of basihyal (191): (0> 1) expanded, with anterior margin with two-thirds or more of its length. Paralleled in Aulixidens eugeniae, Cyphocharax spilotus, and Prodontocharax melanotus .

2. Development of transverse process of neural arch of third vertebra (219): (0> 1) well developed and extending beyond anterior margin of tripus. Paralleled in node 302, and in Agoniates anchovia, Cyanocharax alburnus, Deuterodon langei, Engraulisoma taeniatum, Hemiodus cf. thayeria, and Roeboexodon geryi . Some trees: Paralleled in Microschemobrycon casiquiare and Parecbasis cyclolepis .

3. Process of scapula forming anterior border of scapular foramen (244): (0> 1) absent. Paralleled in nodes 193 and 252 and in Aphyodite grammica, Deuterodon langei, Hoplias cf. malabaricus, Hyphessobrycon herbertaxelrodi, Leporinus striatus, and Odontostilbe paraguayensis .

4. Dorsal-fin rays articulating with first dorsal pterygiophore (266): (1> 0) two. Reversal of synapomorphy 4 of node 203. Paralleled in Bario steindachneri . Some trees: Paralleled in Hyphessobrycon elachys and Paracheirodon axelrodi .