Agnatha is Greek and means "no jaws". It is a superclass of jawless fish. They are cold blooded and has a cartilaginous skeleton, like the sharks and rays.
Recent genetic studies support the theory of a common ancestor to the approximately 100 species of agnathans living today. These are organized in two classes:
- Cephalaspidomorphi is the class of lampreys.
- Myxini includes the hagfish.