Fish are generally covered in scales and have fins and a propulsive tail. There are several classes, Agnatha without jaws, the extinct Placodermi, modern Osteichthyes with a bone skeleton and Chondrichthyes with a cartilage skeleton.

The fish fossil shown in the picture is Osteolepis macrolepidotus. It is a Devonian coelacanth from the Orkney Islands, Scotland.