Tully Monster Mystery

Mystery Solved!

After 50 years of research and mystery, scientists finally pulled together enough evidence to solve the Tully Monster Mystery!

Scientists were able to use something called a synchrotron X-ray machine, which showed them the Tully monster’s physical features in a new way. Have you ever had an X-ray? What do X-ray machines help us do?

X-ray machines allow people, like scientists and doctors, to look inside something, like inside an arm to see if a bone is broken.

As you watch the video below, consider the following:

  • What challenges did scientists face when trying to learn about the Tully Monster?
  • What type of animal have scientists determined the Tully Monster to be?

So what exactly was the Tully Monster?

The Tully monster was a soft bodied creature that lived in the Pennsylvanian period about 300 million years ago. Fossils of this extinct species are found in Mazon Creek near Grundy, Illinois. Tully Monster’s classification has long been the subject of controversy, with some scientists arguing in favor of its classification as a vertebrate, and others as a non-vertebrate. As you learned in the video above, in 2016, the scientific community reached consensus, classifying Tully Monster as a vertebrate. How did scientists make this final determination?

Here's some more Tully Monster trivia!

Amateur paleontologist and fossil collector Francis Tully discovered the first Tully monster fossil in 1958, bringing it to the Field Museum where paleontologists wondered at its unusual structure.

This Tully Monster is the state fossil of Illinois.

Throughout this resource kit, you examined Tully Monster fossils, explored why it was so mysterious, and learned how scientists gathered the evidence they needed to determine what kind of animal the Tully Monster was. Great work!