Prehistoric Sea Monster That Once Roamed Cleveland Waters May Have Been Shorter, Chunkier Than Previously Thought

An armor-plated fish up to 30 feet long controlled the seas some 360 million years ago in the shallow subtropical waters around what is now Cleveland.

Dunkleosteus terrelli was Earth's first vertebrate superpredator during the Age of Fishes, also known as the Devonian Period, when North America was around the latitude of what is now Rio de Janeiro.

Size and Shape of Earth's First Vertebrate Superpredator Miscalculated

A new study, titled "A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira)" published in the journal Diversity, by a doctoral student from Case Western Reserve suggests that the length of the prehistoric sea monster might have been greatly exaggerated.

Russell Engelman, a Ph.D. student in biology at Case Western Reserve and lead author of a study, said that Dunkleosteus is a strange fish that turns out to be shorter and chunkier than previously believed, with a tuna-like torso. Due to that, some of his colleagues have called it "Chunky Dunky" or "Chunkleosteus."

Downsizing the famed Dunkleosteus may not be welcomed the news, according to Engelman, because the giant fish served as Cleveland's mascot regarding paleontology. Dunkleosteus even had a Twitter account for a few years. Being a native Clevelander, he expressed similar sentiments.

The majority of Dunkleosteus study is based on specimens from the Cleveland Museum of Natural History, which holds the world's biggest and finest quality collection of Dunkleosteus remnants. It was discovered by a local company owner named Jay Terrell and a former museum curator named David Dunkle.

Dunkleosteus is such a local landmark that the Ohio General Assembly designated the prehistoric sea monster as the state fossil fish in 2020. Despite this, Engelman said that little study on the fish had been conducted since the 1930s and nearly 150 years since its fossilized remains were discovered on the shores of Lake Erie in 1867.

As Engelman said, there is not much more to say about the species scientifically due to a lack of research. The outdated length estimations were an example of something that is merely passed under everyone's radar since many expected it to be well-studied.

A Fresh Take on Dunkleosteus

The current study estimates the length of Dunkleosteus based on the 24-inch-long head minus the snout. The press release via EurekAlert! reports that Engelman and colleagues considered a way to measure the fish used in groups of living fishes and the smaller relatives of Dunkleosteus. Based on that, the team said the fish could be only 11 to 13 feet long.

Engelman added that after reconstructing the Dunkleosteus, they believe it could have been chunkier as well. They said an 11-foot Dunkleosteus weigh just the same as a 15-foot great white shark. The new calculations on its possible size essentially gave it a tuna-like body and a mouth as wide as a great white shark.

These revised size estimates also assist in placing Dunkleosteus in a larger scientific context. It is part of a bigger tale in which vertebrates evolved from little, inconspicuous bottom-dwellers to gigantic monsters.