Dunkleosteus terrelli was a fish of the placoderm class that terrorized the Earth’s oceans during the Late Devonian Period, between 382 and 358 million years ago. Characterized by thick bony armor around its skull (which would probably have been covered by skin in life), this carnivorous fish could bite its prey with a force ranging between 1,349 and 1,664 lbs. Estimates of its body length used to run as long as 33 feet, but more recently have been scaled down to around 13 feet.
Actually the idea of Dnkleosteus being a giant predator and a “terror of the seas”is now outdated. New research revealed that it was much smaller than previously believed. It was around the size of a great white shark. So although it was a ferocious predator it was not a giant sea monster at all.