Rosmana A.P | Science | Scientific Facts

Around 400 million years ago, the first fishes were born. These fishes are protected by hard scales. These fishes still don't have any fins. Beside that, these fish are classified as a kind of "agnatha" fish due their "jawless" mouth. This kind of fish recently suck planktons and other nutrition from sea water around it. Even, some of them suck blood the other fish.

Actually, these fishes are classified as "Pteraspidomorphi". A family of ancient "jawless" fish. This fish family had been extinct due the development of a fish family which has jaws. With these jaws their food change and their body can grow bigger than before. A jawless fish which eats plankton will grow until it reach some pounds, but it will reach more than hundreds kilograms at a fish with jaws. It because this kind of fish use its jaws to hunts food espescially the other fish. But, no one know this kind of fish will be a sea monster at it's time.

This fish then grows and grows. Even it's species are increase rapidly at that time. Some of them adapted, so they have become a killer in the sea. Even, some of them are covered by not only scale, but also armor made from lisps. Even, this predator fish has mouth which contained sharp teeth which coated by some hard lisp. For example Coelacanth.

The largest carnivorous fishes are "Dunkleosteus". This fish body may grow into 9 meters long. Maybe this fish is the scariest fish in that ever live due it's sharp teeth that almost reach 1/2 meters. This fish is a terror at that time. But, in a short time, these fishes are extinct. No one know why this fish suddenly extinct.

Now, all kind of this primitive fish (pteraspidomorphi, placoderm, etc.) are extinct except Coelacanth, a lob finned fish that was already exist around 200 million years ago and still exsist until now. But, they had descent two kind of fish, Chondrichthyes a family of fish which has skeleton that constructed from cartilages and Osteichthyes a family of fish which has skeleton that constructed from hard bones. These fish are the fishes that were descended from carnivorous fish like "dunkleosteus".