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).