Dunkleosteus – Giant Fish of an Ancient Ocean

Dunkleosteus terrelli Recreation

Dunkleosteus terrelli was one of the largest fish in the ocean, as large as an elephant, and the largest of the armored fish. Armored fish were covered in bony plates that protected them from attack. They had one of the most powerful bites of any fish, too, and the most powerful of any fish without teeth. Instead of teeth, they had a hard, sharp beak that was slightly ridged, giving Dunkleosteus the ability to bite, grab, and chew as well as any fish with teeth. The beak was also self-sharpening, because it was angled in such a way that every bite would sharpen the edges.


Fossil of Dunkleosteus terrelli Head Plates About 350 million years ago, Dunkleosteus lived in the shallow ocean which covered what is now the Northeastern and Midwestern United States. The climate at the time was subtropical, similar to the climate in Vietnam and Northern Mexico.

It was not the first discovery of Dunkleosteus, but the most recently important was in 1966, when an interstate highway was being built in Cleveland, Ohio. The highway was to go through land rich in shale deposits, and a team of researchers from the Cleveland Museum of Natural History helped the state clear them in order to find the countless fossils contained within the shale. One of those fossils was Dunkleosteus, which was classified a year later. It is named after a former curator of the Cleveland Museum of Natural History, David Dunkle, and the man who discovered the species in 1867, Jay Terrell.


In addition to Dunkleosteus terrelli, other Dunkleosteus species, all smaller but still mighty, have been discovered in other areas of North America, in Western Europe, and Northern Africa. There are 10 species known today. One of them, Dunkleosteus denisoni, is known from a dorsal plate which is structured the same but much smaller than Dunkleosteus terrelli. It could be possible that this truly was a different species, but I think it’s also possible that this was a juvenile specimen.

Something else out of the ordinary about Dunkleosteus was that it might have been one of the first fish to internalize the fertilization of eggs, rather than fertilizing them in the water.


Updated Body Shape Dunkleosteus terrelliThe overall shape of Dunkleosteus has had some scientific revision in recent years. In 2017, some new finds revised the back and tail shape to be less like other armored fish and more like a shark. Very few fossils remains have been found of the tail and the back half of the fish in general, and so most of the recreations were guesswork.


Dunkleosteus had the ability to very quickly open and close their jaws in less than a second, and had a bite strength big enough to punch through armor and bone. Because of these facts, it seems likely that Dunkleosteus fed on smaller armored fish. They also did not digest the bones of their prey but regurgitated them instead.

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