March 28, 2023

New research reveals true size of ancient monster fish “Dunk” | Biodiversity

A 360-million-year-old sea monster once thought to be as big as a bus was actually less than half as long, but just as sturdy, according to a new study.

the boneless fish dunkleosteus terrelli, nicknamed “Dunk,” was one of several top predators that roamed the oceans during the Devonian period (419 million to 358 million years ago). This huge armored fish had blade-like jaws that could close with 8,000 pounds of force. Its first fossils D. terrelli they were discovered 150 years ago on the shores of Lake Erie near the city of Cleveland, and the largest known specimen is in the collections of the Cleveland Museum of Natural History in the United States.

Unlike modern fish, which have a cartilage or bony skeleton, D. terrelli it had a bony, armored skull attached to a cartilaginous skeleton. The skull was nearly 85cm tall and resembled the title character of the movie “Alien”.

It turns out that only the skulls of these creatures were fossilized. Thus, early researchers exaggerated its size D. terrelli from the relationship between the size of a shark’s skull and its body length. Over the next 150 years, the species would become a local symbol of paleontology, even prehistoric fish official of the state of Ohio, USA. Despite this, very little scholarly work has focused on the species.

During the pandemic, Russell Engelman, a PhD student at Case Western University in Cleveland, found himself unable to do his usual laboratory research. Instead, he went to the Cleveland Museum of Natural History to ponder some research questions. When examining samples of D. terrelli, Engelmann ran into a problem. “Everything in biology is affected by body size,” he told Live Science. “I tried to use some of the old measurements and biologically they didn’t make sense.”

Try as he might, Engelman could not reconcile the skull with a 30-foot-long body. All of his reconstructions required strange, unrealistic body proportions that looked nothing like the original designs. Naturally, he decided to learn how the original researchers determined the size of fishand that’s when the real problem appeared.

“I looked through the literature and found that most of the previous authors who talked about this were basically just looking,” Engelman said. He then measured the dimensions of several fish skulls and compared them to their body proportions. He found that skull size and shape were highly correlated with body proportions.

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When applied to D. terrelli, this analysis not only excluded the most extreme size estimates, but rejected them all. Rather than being 9 meters long, the fish was probably no longer than 4 meters, Engelman wrote in a study published in the journal Diversity.

Engelman’s analysis looked at many suspect factors, but ultimately came down to height versus skull width. Fish with a longer skull tend to have a more elongated body, while fish with a smaller skull have a shorter body. His relatively short head D. terrelli suggests that it had a short, broad body, more like a tuna than a shark.

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