In the summer of 1955, when Francis Tully set off on a fossil-collecting jaunt some 50 miles south of Chicago, he had no idea that his name was about to go down in paleontological history. A pipe-fitter by trade, Tully was just an amateur collector, but a skilled one. He knew that the coal miners of Mazon Creek had discarded vast piles of shale that contained fossils galore. And as he sifted through the fragments, he found two rocks that had cracked open and that held something incredible between them.
It looked like … an obese foot-long earthworm with a trunk and a spade-shaped tail? “I knew right away. I’d never seen anything like it,” Tully later said. “None of the books had it. I’d never seen it in museums or at rock clubs.” He took it to the Field Museum in Chicago, where it came to the attention of Eugene Richardson, curator of fossil invertebrates. He had no idea, either. He couldn’t work out what the creature was related to, and he couldn’t assign it to any of the major animal groups—a “serious and embarrassing matter,” he wrote.
Whatever it was, it was clearly an abundant part of its ancient ecosystem, some 300 million years ago. Collectors quickly found one specimen after another. Hundreds ended up at the Field Museum. Many more lined shelves in rock shops and private collections. The creature became affectionately known as the Tully monster, and the name became so popular that Richardson felt compelled to formally describe it in 1966. For lack of a better alternative, he simply Latinized the nickname into Tullimonstrum gregarium. (“Darned right,” said Tully.)