The devonian period was as long as 410 to 360 mya it was so long ago that fish rule the seas reptiles did not even evolve yet! In the devonian the first sharks have apeared the sharks nickname was an ironing table because males had the dorsal fin shaped like one.          But this paticular shark was not yet ruling the seas, in                                                                                        
fact there was a much bigger preadator. That mysterios predator that Iam going to tell you in a sec is from the head plated family, does not have real teeth, is a canibal, eats everything he personaly thinks is alive is...
Dunkleosteus, Its so giant it weighs almost 4 tonnes and long up to 10.6 meters but I think it should be miles.
At that time it was known to humans that there was a big population of fish at the devonian which included the big predators such as Dunkleosteus And the shark.