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Paleontologists in Yale-Led Team Solve the Mystery of the Tully Monster

Sean McMahon/Yale University
Tully Monster
The creature belongs to a class of jawless fish that aren’t exactly charming.

Fossils of a sea creature found in the state of Illinois in 1958 have puzzled scientists for decades. But recently a Yale-led team of paleontologists were able to identify the 300-million-year-old animal, known as the Tully Monster.  

It’s been the state fossil of Illinois since 1989. U-Haul trucks and trailers started featuring its image, but nobody knew what it was. Turns out the oddly constructed creature — which grew to only a foot long — was a vertebrate, essentially a fish, according to Derek Briggs, Yale Professor of Geology and Geophysics.

"It looks a little fish-like, but it has a strange horizontal bar, which extends sideways, and the eyes are perched on the end of this," Briggs said. "And then it has a long, trunk-like projection out the front. So it looks like nothing that we’re familiar with."

Fossils of the Tully Monster have been found at only one location, southwest of Chicago. The creature is officially known as tullimonstrum gregarium. 

Briggs said it belongs to a class of jawless fish that aren’t all that charming. 

"Specifically [it belongs] to a group called lampreys, and the lampreys are parasitic," Briggs said. "Ironically, they’re a major pest in the Great Lakes, because they attack what you might call regular fishes by attaching to their sides and rasping away at tissues."

Researchers said there’s still more to learn. No one knows yet when the Tully Monster first appeared or when it became extinct.

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The independent journalism and non-commercial programming you rely on every day is in danger.

If you’re reading this, you believe in trusted journalism and in learning without paywalls. You value access to educational content kids love and enriching cultural programming.

Now all of that is at risk.

Federal funding for public media is under threat and if it goes, the impact to our communities will be devastating.

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