Fish

Fish belong to the Vertebrates. The oldest known fish fossils date from the Lower Cambrian period. The first fish belong to the jawless fish. At the beginning of the Silurian period, the jawed fish appeared. In the Devonian, the armored fish with external skin plates for protection emerged.  The Bony fish (Actinopterygii) and cartilaginous fish (Chondrichthyes) also appeared on the scene. The teeth, possible skin plates and vertebrae are regularly found as fossils. Complete fish are known from many places.