Tully monster mystery SOLVED!
The Tully monster (Tullimonstrum gregarium) is a weird creature. It was first discovered by an amateur collector, Francis Tully, in 1955 and the original specimens ended up at The Field Museum. Only found in the Mazon Creek formation of Illinois, it quickly gained the affection of the public and scientists alike, and became the state fossil in 1989.
The only problem was that nobody knew what, exactly, the monster was. For decades, the Tully monster was classified as an invertebrate, perhaps related to annelid worms, or arthropods. But back in March, a paper co-authored by Field scientists was published in the science journal Nature, and it finally cracked the mystery: Tully monsters are vertebrates! and closely related to lampreys.
By: The Brainscoop.