Placodermi

The armored fish – or placoderms – derive their name from the numerous bony plates that form an armor on their head and upper body. The abdomen and tail were either covered with scales or remained naked. Placoderms ruled the water during the Early Paleocene. With a body length between six and eight meters, Dunkleosteus was one of the largest placoderms. Its jaws, which showed jagged rims with sharp cutting edges instead of teeth, reveal it as a dangerous predator.