Tullimonstrum

Tullimonstrum, colloquially known as the Tully monster or sometimes Tully's monster, is an extinct genus of soft-bodied bilaterian marine animal that lived in shallow tropical coastal waters of muddy estuaries during the Pennsylvanian, about 310 million years ago. A single species, T. gregarium, is known. Examples of Tullimonstrum have been found only in sediments deposited far from the palaeocoast (formally termed the Essex biota), in the Mazon Creek fossil beds of Illinois, United States. Its classification has been the subject of controversy, and interpretations of the fossil have likened it to molluscs, arthropods, conodonts, worms, tunicates, and vertebrates. This creature had a mostly cigar-shaped body, with a triangular tail fin, two long stalked eyes, and a proboscis tipped with a mouth-like appendage. Based on the fossils, it seems this creature was a nektonic carnivore that hunted in the ocean’s water column. When Tullimonstrum was alive, Illinois was a mixture of ecosystems like muddy estuaries, marine environments, rivers and lakes.