In 1958 fossil collector Francis Tully made a peculiar discovery south-west of Chicago, Illinois. Dating from 307 million years ago, the unusual creature seemed to have fins like a cuttlefish, a long tube-like structure with teeth at the end and widespread eyes like a hammerhead shark. Nobody knew whether it was a vertebrate, a mollusc, a type of worm or something entirely different. It was named the Tullimonstrum gregarium and has puzzled palaeontologists for decades.
Now however, after analysing over 1200 specimens of this bizarre creature, British palaeontologist Victoria McCoy and her colleagues from Yale university have shed light on the 58 year old mystery. They’ve determined that the Tully monster was a kind of early vertebrate called a chordate (pronounced KOR-date). Instead of a solid backbone it had a cartilage like structure called a notochord (pronounced NO-toh-kord). It measured roughly 35 centimetres in length, its teeth were made from keratin and it had crescent-shaped nostrils. It’s unclear whether it was a predator or a scavenger but it was almost certainly a distant ancestor of the lamprey.
The Tully monster would have fed by grasping other creatures with its mouth and scraping off bits with its tongue, much as the modern lamprey feeds. It was definitely an odd-looking creature, but now it can take its proper place in palaeontological textbooks.