Tullimonstrum gregarium
From Palaeos
[edit] Discovery
The Tully Monster (Tullimonstrum gregarium) was first discovered in 1958 by amateur fossil hunter Francis Tully. It has only been found at the Mazon Creek Lagerstätten, and thus is limited to the Pennsylvanian. It has been named the state fossil of Illinois.
[edit] Description
The Tully Monster was a soft-bodied, nektonic organism that lived in the shallow tropical coastal environment of Palaeozoic Illinois. Its bauplan is at least somewhat unique - it had a diamond-shaped tail and a large rounded main body, ending in a long proboscis containing small teeth. Shortly aft of the proboscis in many specimens is a bar-shaped structure, interpreted by some as a support structure for its eyes. Shortly fore of this structure is a crescent shaped slit interpreted as a mouth. A small opening can be seen in some specimens where the body meets the tail that may be interpreted as an anus. Some reconstructions show the Tully Monster as segmented, but the structures interpreted as segmentation lines may just be the result of the decay of the creature prior to fossilization. Individuals ranged in length from 5 inches to over 1.5 feet.
