The Tully Monster is an eel-like sea creature that lived about 300 million years ago during the Pennsylvanian Epoch of the Carboniferous Period of geologic time. This sea creature had a torpedo-shaped body and a jointed trunk-like snout that ended in a claw-like proboscis having two rows of teeth. Its eyes were set on the ends of a long rigid bar extending sideways from the head.

Its fossilized remains were first discovered in 1958 by an amateur fossil hunter by the name of Francis Tully. He was unable to identify the fossil and took it to paleontologists at the Field Museum of Natural History in Chicago. They too were unable to identify the specimen and referred to it as the Tully Monster. The name stuck when Dr. Eugene Richardson formally described the new sea animal as Tullimonstrum gregarium.

The fossil is fairly common in the Mazon Creek fossil beds of Illinois in outcrops known as the Francis Creek shale. In 1989, the Tully Monster was designated as the state fossil of Illinois.

Recent studies have concluded that the sea creature was an ancient lamprey. See the article in the Scientific American. https://www.scientificamerican.com/article/tully-monster-mystery-solved-scientists-say/

More Info: www.museum.state.il.us