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Tully Monster

Illinois State Fossil

Tully monster fossil and model at Chicago Field Museum; photo by Brian Smith (brianbrarian) on Flickr (noncommercial use permitted with attribution / share alike).

Official State Fossil of Illinois

The Tully monster (Tullimonstrum gregarium) was designated the official state fossil of Illinois in 1989. All State Fossils

The Tully monster was a soft-bodied prehistoric marine animal which lived 280 to 340 million years ago during the Pennsylvanian geological period. So far Tully monster fossils are unique to Illinois - more than 100 Tully monster fossils have been found in the state (amateur collector Francis Tully found the first in 1958).