Sean McMahon Reconstruction of the Tully Monster as it would have looked 300 million years ago, swimming in the Carboniferous seas. Notice the jointed proboscis, the multiple rows of teeth, and the dorsal eye bar. 4 more images in gallery The “Tully monster,” a mysterious animal that swam in the inland oceans of Illinois more than 300 million years ago, left behind a tantalizingly detailed map of its body in a well-preserved package of fossils. Unfortunately, nobody could figure out what the creature was for half a century—until now. Francis Tully found the remains of the tiny beast (it’s only about 10 centimeters long) in Illinois in 1958 and gave it the whimsical scientific name Tullimonstrum  (nickname: Tully monster). A long stalk extends from the front of its body, which ends in a toothy orifice called a buccal apparatus. Its body is covered in gills and narrows down into a powerful tail that it probably used for propulsion. Its eyes peer out from either end of a long, rigid bar attached to the animal’s back. The Tully monster lived during the Carboniferous period, when the North American Great Basin was an enormous inland sea. Trees were colonizing the land for the first time, transforming the soil and filling the atmosphere with higher levels of oxygen than Earth had known before or since. Giant arthropods, like the 8-foot-long millipede known as  Arthropleura , crawled through the new forests. It was a good time to be a weird animal, and the Tully monster probably fit right in. Read 3 remaining paragraphs | Comments

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307-million-year-old “monster” fossil identified at last