advertisement continue reading the main story “ the frustrating thing is that these morphological features are similar to eye stalks found in crabs and insects .
since 1955 , when amateur fossil hunter francis tully discovered the unlikely prehistoric creature in a coal mining area near morris , the thing that would be named the tully monster has presented one of the great puzzles in paleontology .
the tully 's renown stretched even to the illinois state legislature , which named it the official state fossil in 1989 , some 308 million years after it inhabited the shallow salty waters that turned into the state 's mazon creek geological deposits , in grundy county , one of the richest fossil troves on earth .
utilizing the synchrotron x - ray machine at argonne and the field museum 's collection of 2,000 tully specimens , a team from those two institutions , yale university and the american museum of natural history announced in a paper published in the journal nature wednesday that " the tully monster is a vertebrate . "
others assumed it was an arthropod like a snail .
the creature was named after francis tully , the amateur who discovered it in 1958 in the mazon creek in illinois .
to come to their conclusion , team members first pored over 1,200 tully monster specimens from museums .
below that headline , the paper describes since it was first uncovered more than a half a century ago , this kooky - looking creature known as the “ tully monster ” has puzzled paleontologists who , frankly , could not make heads , tails or claws of its fossilized remains .
now , a team of researchers from yale university say they have figured out the monster ’s identity : it ’s a vertebrate most closely related to the lamprey , an underwater bloodsucker .