About a dozen species have been identified under this endangered genus, Dunkleosteus. These terrifying fish, with their powerful jaws, head, body, and heavy armor, roamed the oceans 358-382 million years ago. The biggest feature was the jawbones, which closed very quickly. Fossils. Fossils have been found in North America, Belgium, Poland and Morocco. Of these, the terrelli is thought to be 8.8 m long. Instead of teeth, it had two large beak-like blades.