Subclass
Petromyzoniformes Goodrich, 1909
Classification
| Organism group | Biota |
| Kingdom | Animalia |
| Phylum | Chordata |
| Subphylum | Vertebrata |
| Superclass | Agnatha |
| Class | Cephalaspidomorphi |
| Subclass | Anaspida |
| Galeaspida | |
| Osteostraci | |
| Petromyzoniformes |
| Organism group | Biota |
| Kingdom | Animalia |
| Phylum | Chordata |
| Subphylum | Vertebrata |
| Superclass | Agnatha |
| Class | Cephalaspidomorphi |
| Subclass | Anaspida |
| Galeaspida | |
| Osteostraci | |
| Petromyzoniformes |