Cleveland's cherished prehistoric sea creature turned out to be more turtle than shark

Approximately 360 million years ago, the area now known as Cleveland was ruled by a formidable hunter. Unlike land predators, this 14-foot-long Dunkleosteus terrelli dominated the waters of the shallow Devonian sea. Encased in armored plates and armed with bone blades instead of conventional teeth, it stood as an undisputed apex predator of its era.

For nearly a century, paleontologists have regarded Dunkleosteus as a classic example of the extinct, shark-like arthrodire fishes. However, a recent anatomical study has revealed that traditional depictions of this ancient giant may be far from accurate. The last detailed study on Dunkleosteus jaw anatomy dates back to 1932, a time when arthrodire anatomy was poorly understood, said Russell Engelman, a biologist at Case Western Reserve University in Ohio. Back then, the main focus was simply reconstructing how the bones fit together.

Engelman, along with a team of international researchers from Australia, the United Kingdom, and Russia, examined the largest and best-preserved Dunkleosteus fossils housed at the Cleveland Museum of Natural History. Their findings, published in The Anatomical Record, offer a refined view of the fishs anatomy, especially its head and jaws.

Contrary to previous beliefs, Dunkleosteus emerges as an evolutionary outlier among arthrodires. Nearly half of its skull was composed of cartilage, including key muscle attachments and jaw connections. While many of its relatives developed true teeth, Dunkleosteus and a few related species retained bony blade-like structures in their mouths. This adaptation was not a primitive holdover, but a specialized trait that enabled them to thrive.

New evidence suggests that Dunkleosteus had a head and jaw more similar to a snapping turtle than a shark, allowing it to remove large chunks of prey rather than taking smaller bites. These discoveries demonstrate that arthrodires were not uniform, primitive fishes but a diverse group that occupied a wide range of ecological roles, Engelman explained.

These updated findings do not diminish Dunkleosteuss fearsome reputation; if anything, they make the idea of encountering one even more daunting. Fortunately for visitors of Lake Erie, even this top predator ultimately disappeared during the end-Devonian extinction roughly 358 million years ago.

Reevaluating Dunkleosteus: A New Perspective on an Ancient Predator

The recent anatomical study of Dunkleosteus terrelli offers a groundbreaking revision of our understanding of this prehistoric apex predator. For decades, scientists have viewed it as a classic example of a shark-like arthrodire fish, but new evidence suggests a much more complex and specialized creature. The findings challenge traditional depictions, reshaping how we interpret the evolutionary history of ancient marine life.

Previously, Dunkleosteus was believed to have shark-like jaws, with a structure based primarily on bony plates. However, the latest study, led by Russell Engelman and his international team, reveals that nearly half of Dunkleosteus's skull was made of cartilage, a feature far more reminiscent of reptiles such as snapping turtles than typical fish or sharks. This change in perspective highlights the diversity within arthrodires, an ancient group of fishes that evolved a variety of ecological niches.

Additionally, the new research emphasizes Dunkleosteus's unique jaw mechanics, which allowed it to remove large chunks of prey with bone blades rather than the conventional biting action of sharks. This adaptation likely contributed to its dominance in the Devonian seas. The discovery reinforces that Dunkleosteus was not simply a primitive relic, but a highly specialized predator perfectly adapted to its environment.

While these new insights reshape our understanding, they do not lessen Dunkleosteus's terrifying reputation. On the contrary, they make it even more formidable in the context of prehistoric life. For modern-day observers, the realization that such an extraordinary creature once roamed the waters of what is now Cleveland adds a layer of awe and respect for the ancient oceans that shaped our planet.

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• Cleveland’s beloved ancient sea monster was more turtle than shark