| 1a. | Body oval-shaped and laterally compressed; lateral line arched high anteriorly | Family Lamprididae Opahs |
| 1b. | Body elongate; much longer than deep | 2 |
| 2a. | Anal fin absent; caudal fin long and at right angle to body | Family Trachipteridae Ribbonfishes |
| 2b. | Anal fin present; caudal fin not at right angle to body | 3 |
| 3a. | Two anal fins; three dorsal fins | Family Gadidae Cods |
| 3b. | One anal fin; 2 dorsal fins (anal and second dorsal may be deeply notched) | Family Merlucciidae Merluccid Hakes |