The Chunky Dunkleosteus

Not as big as once believed but still very, very deadly.

With a bite that could split a shark in two, Dunkleosteus was one of the Earth's earliest apex predators, terrorizing subtropical seas 360 million years ago.

By some estimates, it was as long as a school bus. But a new study shrinks it quite a lot.

Russell Engelman, a paleontologist pursuing his Ph.D. at Case Western Reserve University in Cleveland recently compared the proportions of Dunkleosteus's armor clad-head with the skull sizes of hundreds of living and fossil fish.

In the journal Diversity, Mr. Engleman concluded that the ancient predator was only 13 feet long, or four meters, at most.

For the study, Mr. Engleman examined several Dunkleosteus terrelli specimens at the Cleveland Museum of Natural History. Many of these fossils had been discovered nearby, in cliffs along the Rocky River.

But because most of the creature's body seems likely to have been anchored to fragile cartilage that didn't fossilize, only the thick armor plates that encased its head and neck were preserved as fossils.

According to Mr. Engelman, head length is a reliable proxy for body size in fish : short fish species generally have shorter heads, and long fish species longer heads.

Extrapolating from his measurements of hundreds of fish, he arrived at a length generally a bit more than 11 feet. [ Jack Tamisiea ].


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