Agnatha:
These are the most primitive, and the most scarce of all the classes. Agnatha fish have a circular mouth instead of a jaw. However, the presence of sharp teeth makes them a deadly predator.
Chondrichthyes:
This class has sharks, rays, and skates in it. Despite the lack of bony structure, cartilage holds the body together.
Only speaking of sharks, there are over 400 species. Talk about the variety!
These are the bony fish. They have more than 20,000 species making them the largest of the vertebrate groups!
Most of them have jaws and teeth. However, some bony are toothless.