Sean McMahon / Yale University

The Ancient Tully Monster No Longer Totally Defies Classification

After extensive scanning and computer analysis, researchers say Tullimonstrum gregarium was probably most closely related to today's lamprey eels.

By Evan Thomas | March 16, 2016

No, this isn't a collection of spare parts. It's an ancient water-dwelling creature called Tullimonstrum gregarium.

Scientists call it the Tully monster for short, after fossil hunter Francis Tully, who found the first specimen in 1958.

It's thought to have roamed proto-Illinois some 307 million years ago, back when the region was largely underwater. Researchers say its stalked eyes and mouth full of teeth probably mean it was a predator.

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Other details have been harder to pin down. Since it was discovered, there's been some understandable confusion over where the foot-long Tully monster fits, evolution-wise.

"With dinosaurs, we're pretty certain they look like lizards. But the Tully monster looks like a ton of different things. It looks like a fish, it looks like a snail, it looks something like a worm," said Yale University's Erin Saupe.

But researchers at Yale University have now created digital records of thousands of fossilized Tully monsters, and they say Tullimonstrum has a rudimentary spinal cord, meaning it's technically a vertebrate. They're more closely related to today's lampreys and other jawless fish than molluscs or worms.

So there's that burning evolutionary question answered. The team's findings are published in the journal Nature.

This video includes clips from Argonne National Laboratory and David Hewlett / CC BY 3.0 and images from Sean McMahon / Yale University and Paul Mayer / Field Museum of Natural History.

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