For almost six decades, paleontologists were troubled by the bizarre Tullimonstrum gregarium fossils. This creature did not fit into any known major animal group, until now.
Scientists finally believe they have solved the mystery behind the Tully monster and where it lies on the tree of life, according to a new report published in the journal of Nature
The fossils, discovered by the dozens in 1958 inside Illinois coalmines, were found in a 300-million-year-old rock.
The largest fossil stretched to only a foot long. Through reassessment of those ancient fossils, scientists were able to determine that the Tully monster was indeed a vertebrate because it had a rudimentary spinal cord.
Scientists analyzed 1,200 specimens to better understand the Tully monster's form.
Piecing together clues about the way the creature's muscles decayed and other characteristics, scientists were able to conclude that the animal was most likely an eel-like creature similar to the modern-day bloodsucking lamprey, a jawless fish with a funnel-like sucking mouth covered in sharp teeth.
Some of the Tully monster's features are similar to the lamprey, but the ancient creature still has some unique quirks to its anatomy, such as its tiny beady eyes attached to the stalk the runs across its head.
For years, scientists theorized because of the creature's wormlike body and other strange features that it may have been a segmented worm or a swimming slug.
There was even folklore conjured up that the Loch Ness monster
was actually a giant Tully monster, a claim that self-proclaimed monster hunter F. W. Holiday spread around. His theory was later retold by writer Richard Ellis in the book "Monsters of the Sea."
But those hypotheses have now been put to rest, ending a decades-long debate over the nature of the Tully monster and finally giving the creature an animal group it can call home.