Today, the state of Ohio is hundreds of miles away from any ocean. But during the Late Devonian Period, approximately 360 million years ago, our local landscape—and the rest of the Earth, for that matter—looked vastly different.
Dinosaurs wouldn’t appear for 130 million years. It would be another 230 million years before the first flowering plants bloomed. And the area we now know as Ohio was located south of the equator, covered in a tropical sea teeming with ancient marine life.
This ecosystem was diverse, and ancient species thrived in the warm, shallow waters. Vertebrates such as placoderms (an extinct group of fish with armored skulls), early sharks, and many other types of fish lend the Devonian Period its nickname, the Age of Fishes. But they shared the waters with invertebrates, too—from crustaceans to snails to brachiopods.
The ruler of those waters, however, was a giant armored fish known as Dunkleosteus terrelli.
A visitor observes the immersive Dunk exhibit in the new Evolving Life Wing.
Dunk was a fierce predator—so fierce, it required no teeth to hunt. Instead, Dunkleosteus had blade-like jawbones that sharpened themselves when the fish opened and closed its mouth. This was made possible by a hinge at the top of Dunk's head, allowing both its upper and lower jaws to move—and enabling the fish’s mouth to open to a startling 45-degree angle. (For comparison, when a human opens their mouth, only the lower jaw moves, while the rest of the skull stays still.)
These characteristics make Dunkleosteus terrelli an arthrodire, a member of a group of animals that went extinct at the end of the Devonian Period. While many arthrodires lived during this period, Dunk was the apex predator both of this group and on Earth—meaning it was at the top of the food chain.
Visitors look up at casts of Dunkleosteus in the Visitor Hall.
Millions of years later, the fierce fish is now a star among the specimens featured in the transformed Cleveland Museum of Natural History. In the Museum's Visitor Hall, in an exhibit sponsored by Tammy and Dennis Matecun, casts of Dunk fossils are connected to silhouettes that represent scientists’ estimates of the species’ full size, helping you to imagine what a living Dunkleosteus may have looked like.
In the Sears Dynamic Earth Wing, you can see multiple Dunk fossils of different sizes, as well as a full-scale model that appears to swim overhead.
And if you wander into the Dunk in Action area of the Evolving Life Wing, you'll find yourself surrounded by fossils and stunning visuals in an immersive, media-enhanced exhibit that illustrates and animates the true size and power of the apex predator.
Why, you might wonder, is the Cleveland Museum of Natural History such a treasure trove of Dunkleosteus fossils? It all ties back to a geologic formation known as the Cleveland Shale. Millions of years ago, this layer was made up of mud on the seafloor. When Dunkleosteus and other animals died and sank to the bottom of the sea, they were eventually covered by these muddy sediments. Over the course of millions of years, more and more sediments piled up and hardened to become shale, a type of sedimentary rock. This process helped to preserve Dunkleosteus and many other Devonian species as fossils.
Today, Dunkleosteus fossils can still be found in the Cleveland Shale throughout Northeast Ohio. Fossils of Dunk’s armored head are typically found in pieces—requiring a painstaking process to assemble them into their original, three-dimensional form. And while Dunk’s skull bones preserved well as fossils, its body—which was composed of cartilage, like a shark’s—did not.
To this day, no Dunkleosteus body has been found, and paleontologists have spent the past 150 years trying to determine what this body would have looked like. Estimates of the fish's length range from 9.8 to 33 feet (3 to 10 meters).
The first Dunkleosteus fossils ever found were discovered in 1867 by amateur fossil collector Jay Terrell in the cliffs along Lake Erie. Museum scientists including Peter Bungart, Dr. David Dunkle, and Dr. Jesse Earle Hyde discovered additional fossils, including some in the Rocky River Reservation. And many more fossils were unearthed during the expansion of Interstate 71 in the 1960s by Dr. Bill Hlavin, the Museum’s former Associate Curator of Vertebrate Paleontology and a current Board member.
Paleontologist Peter Bungart is pictured with an early reconstruction of Dunk fossils.
Thanks to these efforts, the Cleveland Museum of Natural History is now one of the foremost places to study Ohio’s Late Devonian ecosystem. It houses such a diverse collection of Dunkleosteus fossils that paleontologists can study the variations among them. And while you can now find fossils and casts of Dunkleosteus terrelli and its relatives in museums around the world, the Museum's collection is the largest and best preserved. In 2020, the Ohio General Assembly passed a bill declaring Dunkleosteus terrelli the state fossil fish in honor of its significance to our region.
Curious to learn about the other life in ancient Ohio? In addition to its many Dunk fossils, the Museum’s Cleveland Shale collection includes invertebrate, paleobotany, and other vertebrate specimens—and you can see many of them on view throughout the Museum’s new wings. Plan your visit today!
