There are many systems of classifying fish, some extremely complicated. The classification given here is basically the one adopted by the American Fisheries Society. Fish are grouped in the superclass Pisces, which consists of three classes:
The Agnatha:
lampreys and hagfishes. They have no jaws and have undeveloped backbones. They are the most primitive of all fish. Some biologists do not classify them as fish.
The Chondrichthyes:
sharks, skates, and rays. Fish in this class have no bones. Their skeletons are made of cartilage.
The Osteichthyes:
the bony fishes. They have skeletons composed partly or wholly of bone. This class is divided into two subclasses:
I. Sarcopterygii
fishes with lobed, fleshy fins, such as lungfishes and lobefins.
II. Actinopterygii
the higher bony fishes. This subclass consists of many orders, including:
1. Acipenseriformes.
2. Semionotiformes.
3. Amiiformes.
4. Elopiformes.
5. Anguilliformes.
6. Clupeiformes.
7. Salmoniformes.
8. Myctophiformes.
9. Cypriniformes.
10. Siluriformes.
11. Percopsiformes.
12. Batrachoidiformes.
13. Lophiiformes.
14. Gadiformes.
15. Atheriniformes.
16. Zeiformes.
17. Lampridiformes.
18. Gasterosteiformes.
19. Perciformes.
20. Pleuronectiformes.
21. Tetraodontiformes.