What's A Tully Monster? Now We Know.

Mar 16, 2016

The Tully Monster Mystery has been solved. New research published in the journal "Nature" sheds light on Illinois' state fossil.

Tully Monster fossil
Credit Illinois State Museum

It’s been about 300 million years since the strange creature known as the Tully Monster swam in the salty waters of central Illinois. The mystery of just what it was has been brewing since a fossil hunter discovered it near Morris in 1955.

The foot long soft-bodied creature earned the name “monster” because it was, well…just so weird-looking. It had tailfins at the back of its soft body, its eyes were perched at the ends of a horizontal bar, it had a long, thin nose with teeth. But it couldn’t be classified, so it ended up in a category known as “problematica.” But new research on Field Museum fossils using Argonne Laboratory technology has placed the Tully Monster into its proper biological category: vertebrate. Researchers were finally able to see its primitive backbone, and could draw a link to today’s lampreys.

The Tully Monster has only been found, and in great numbers, in the Mazon Creek area in Grundy and Will counties.