About 360 million years ago, present-day Cleveland was home to a fearsome predator. But this giant did not stalk prey on land. Instead, the 14-foot-long Dunkleosteus terrelli swam through the region's shallow Devonian sea. Covered in armor plates and featuring scalpel-sharp, bone blades for teeth, Dunkleosteus was an undisputed, ancient apex predator.
Most paleontologists have considered it an iconic representation of the long-extinct, shark-like group known as arthrodires for nearly a century. But according to a new anatomical study, researchers now believe those early Dunkleosteus depictions are wildly inaccurate.
"The last major work examining the jaw anatomy of Dunkleosteus in detail was published in 1932, when arthrodire anatomy was still poorly understood," Russell Engelman, a biologist at Ohio's Case Western Reserve University, said in a statement. "Most of the work at that time focused on just figuring out how the bones fit back together."
Engelman recently collaborated with an international team of researchers from Australia, the United Kingdom, and Russia to analyze the world's largest and most well-preserved collection of Dunkleosteus fossils at the Cleveland Museum of Natural History. Their results, published in The Anatomical Record, provide a much more accurate estimate of the creature's anatomy, particularly its head and jaws.
Surprisingly, it now appears Dunkleosteus was an "evolutionary oddball," compared to its fellow arthrodires. Almost half its skull was made of cartilage, including most muscle attachment locations and major jaw connections. And while most of its relatives grew actual teeth, Dunkleosteus and a few other similar species retained a mouth full of bony blades.
This mouth structure wasn't an evolutionary relic, however. It was actually a specialized feature that allowed them to thrive. It now appears Dunkleosteus boasted a head and jaw more reminiscent of a snapping turtle than a shark. This allowed them to tear off large chunks of their prey instead of attacking with smaller bites.
"These discoveries highlight that arthrodires cannot be thought of as primitive, homogenous animals, but instead a highly diverse group of fishes that flourished and occupied many different ecological roles during their history," explained Engelman.
The paleontological revisions to Dunkleosteus don't reduce its fearsome reputation. If anything, they may make the thought of encountering one even more terrifying. Luckily for Lake Erie's visitors, even an apex predator like Dunkleosteus ultimately succumbed to the end-Devonian extinction event roughly 358 million years ago.