ROCKFORD, Ill. (WTVO) — Illinois is not among the greatest places to find ancient creatures, but the state’s fossil is surely among the most interesting.

Did you know Illinois had a state fossil? It’s Tullimonstrum, also known as Tully’s Monster. The creature has only been found in the Mazon Creek fossil beds of northeastern Illinois and a some spots in central Illinois.

Few creatures in the fossil record have perplexed paleontologists more than the Tully Monster, according to Scientific American. The monster possessed a “toothy, trunklike” snout and eyes set far apart on a rigid stalk like a slug.

Scientists have struggled to determine what exactly a Tully monster is. It’s been grouped with segmented worms, swimming slugs and primitive eel-like critters.

According to Illinois State Museum, Francis Tully found the first one in 1958. He took it to experts at the Field Museum of Natural History in Chicago for identification, but the scientists were stumped. Museum staff with a sense of humor nicknamed it the “Tully Monster.”

The monster was thought to hunt 300 million years ago, when Illinois was closer to the equator and covered in water.