by Mary Caperton Morton Thursday, July 14, 2016
In 1958, an amateur fossil collector named Francis Tully found a strange fossil in a quarry near Morris, Ill., southwest of Chicago. Thousands more of the worm-like Tullimonstrum gregarium, better known as the “Tully monster,” were recovered from the same deposit — now a National Historic Landmark called Mazon Creek fossil beds. But the creature’s full appearance and just what sort of animal the Tully monster was have remained mysteries. In a new study, researchers have now finally identified it as a jawless fish, similar to modern lampreys.
Tully monsters lived roughly 307 million years ago along a swampy shoreline at the edge of a shallow inland sea. The odd-looking, soft-bodied animals were tube-shaped, with eyes at the end of short stalks, like a snail, and a long toothed snout that it might have used to probe for prey in the mud. Its peculiar shape led scientists to suggest over the years that Tully monsters belonged variously to families of worms, gastropods, arthropods or eel-like conodonts.
The examination revealed that “the monsters are related to the jawless fishes that are still around today by a unique combination of traits, including primitive gills, rows of teeth, and traces of a notochord, the flexible rod-like structure along the back that’s present in chordate animals — including vertebrates like us,” said Paul Mayer, the Field Museum’s Fossil Invertebrates Collections Manager and a co-author of the study, in a statement.
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