Exploration HQ Highlight: Dunkleosteus Jaw


Exploration HQ Highlight: Dunkleosteus Jaw 

By: Michael Fouts

If you visit the Ohio History Center anytime this February you can stop by our hands-on Exploration HQ station to see a life sized reproduction of a Dunkleosteus jaw plate and many other amazing fossils! Check out my previous blog post about the Dunkleosteus for an overview on this spectacular creature. In this post I’m going to go into more detail about this amazing predatory fish.  

Dunkleosteus was a genus of the now extinct class of armored plated fish known as Placoderms (a name which literally means, “plate-skinned”). The largest species of this genus, Dunkleosteus terrelli, was an apex predator that swam in the subtropical Devonian waters that covered much of Ohio about 359 million years ago. Dunkleosteus ruled over a kingdom filled with tasty prey. From fossil evidence we know that the seas of this period were full of life. Sometimes dramatically referred to as the “Age of Fishes,” many fossilized sharks and ray-fined fish have been found in Ohio’s Devonian deposits. Without a doubt the largest of those fossils found in the area belong to Dunkleosteus.

A 1972 Placoderm display at the Rocky River Nature Center. (Image: Cleveland State University Library Special Collections)

D. terrelli was an intimidating animal that reached lengths of up to 20 feet and is estimated to have weighed in at about one ton (2,000 pounds!). So far the only remains that have been found of this fish have been their massive skulls made up of multiple bony plates. Popular reproductions of Dunkleosteus often depict these bony plates on the outside like a suite of armor, but they were actually covered by skin. Their estimated length, weight and overall body shape have come from studies based on the dimensions of their skulls and the more complete fossil remains of other related fish.

Aside from its massive size, perhaps the most terrifying aspect of Dunkleosteus were its razor sharp jaw plates that it used to shred apart its prey. The two lower jaw plates were about as long as an adult human forearm and were tipped by protruding, pointed cusps that were used for gripping and holding prey. Dunkleosteus did not have traditional teeth that we see in fish today. Instead, parts of the exposed upper and lower jaw plates came together to form a scissor-like cutting edge that would also self-sharpen every time the jaws opened and closed.

Dunkleosteus had sharp bone plates inside of their mouths rather than traditional teeth. (Image: The Jesse Earl Hyde Collection, Case Western Reserve University Department of Geological Services) 

Not only did the Dunkleosteus have razor sharp mouth plates, but they also had an interior muscle design that gave them some surprising advantages while hunting. Opening its mouth muscles on the head contracted moving the skull along with the upper jaw backwards and up. The hinged lower jaw was also pulled by muscles back and downwards. As a result, the mouth could snap open to as wide as 45 degrees in less than a second. This action would effectively create a vacuum that would bring in any unfortunate victim closer to its waiting jaws. The muscular structure of its head not only created a unique suction effect, but the force of the bite created by Dunkleosteus was estimated to be about 80,000 pounds per square inch at certain points of the jaw.

Fossil evidence suggests that Dunkleosteus had a habit of cannibalizing on its own kind. (Image: Lee Hall, Cleveland Museum of Natural History)

The reign of the Dunkleosteus, of course, did not last forever. At the end of the Devonian Period, around 359 million years ago, there was a massive extinction. Around 70 percent of all species on earth perished and the Dunkleosteus was no exception. Today, you can see the actual fossilized remains of Dunkleosteus at the Cleveland Museum of Natural History on display in the Kirtland Hall of Prehistoric Life. The genus name Dunkleosteus was given in honor of the former curator of Vertebrae Paleontology at the Cleveland Museum of Natural History, Dr. David Dunkle, who, in 1867, helped discover the first fossils of the long extinct fish genus.     

If you would like to learn more about these amazing creatures stop by the Ohio History Center and visit Exploration HQ any time this February to see a life size reproduction of a Dunkleosteus jaw plate. And if you would like to learn more about these amazing prehistoric predators right now, check out this blog from the Cleveland Museum of Natural History!
 

Posted February 1, 2019
Topics: All Topics

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