The Tully Monster is an enigmatic creature that lived in a muddy estuarine environment during the Carboniferous Period, about 307 million years ago. It is known only from the Mazon Creek fossil beds, a rich deposit in northeastern Illinois that records a diverse forest, river, and estuarine ecosystem. Fossils from Mazon Creek are found in nodules made of siderite (iron carbonate), and they often preserve delicate soft parts that do not usually fossilize.
Since its discovery in 1955, scientists have debated what type of animal the Tully Monster is. It has been interpreted in many different ways, including as a mollusk, worm, and arthropod. Most recently, it has been identified as a primitive relative of lamprey fish, based on its preserved eye structure. The Tully Monster is named after its discoverer and is the state fossil of Illinois. It probably used its long proboscis to probe for small prey and edible matter in the mud.
- Measures 12"