Dunkleosteus was a large early fish known mainly for its armored skull and frontal area, because this is the only area that has been reliably preserved in fossils. This skull featured immensely strong jaws with the most powerful bite force of any living or extinct fish. Though it was toothless, it made up for its lack of teeth by having sharp-edged, blade-like armored jaw plates in its mouth.
The rest of the body of Dunkleosteus is still something of a mystery. Scientists have tried to imagine what its body looked like, by comparing it with more completely known related fish, as well as comparing measurements and proportions of other fish, both extinct and living.
Because of the incomplete nature of its fossils, size estimates for Dunkleosteus are wide ranging. Scientists think it could have been anywhere from 13 to 33 feet long. In any case, it was a large fish, and definitely one of the biggest things swimming around 350 million years ago.
Some reconstructions of Dunkleosteus show its body more elongated, with a tail similar to eels. Other, more recent reconstructions portray it with a shark-like tail. The most recent proposals have greatly adjusted its body size, giving it a much more compact, stout appearance.