To say that paleontologists can’t make heads or tails of the Tully Monster would be untrue. The claw-tipped proboscis on the front end and the arrow-shaped rear fins at the posterior end can be easily identified in complete specimens. Beyond that, though, this 300 million year old invertebrate remains one of the most vexing fossil species ever found.

Tully Monsters first came to the attention of paleontologists in 1958. While looking for fossils among the mining pits of northeastern Illinois, collector Francis Tully stumbled across an assemblage of marine organisms unlike any found elsewhere in the area. Especially perplexing were six-inch, worm-like impressions found inside the numerous concretions that littered the pits. Soon other amateur fossil