Illinois State Fossil

Tully Monster

(Tullimonstrum gregarium)

Adopted in 1989.

Illinois State Geological Survey paleontologist Donald Mikulic lobbied the State Legislature for designation of the Tully Monster,( Tullimonstrum gregarium,) as Illinois state fossil, and a bill to this effect was passed in 1989.

Illinois State Fossil: Tully Monster

Tullimonstrum gregarium, colloquially known as the Tully Monster, was a soft-bodied invertebrate that lived in shallow tropical coastal waters of muddy estuaries during the Pennsylvanian geological period, about 300 million years ago. Examples of Tullimonstrum have only been found in the Mazon Creek fossil beds of Illinois, United States.

It is a soft bodied animal. It preserves as outlines and flattened forms in nodules of ironstone from several areas in Illinois. It lived in the ocean that covered much of Illinois during the Pennsylvanian Period (about 300 million years ago). It was probably an active, swimming carnivore.

The flexible body was probably round or oval in cross section. It may have been segmented, but some recent work suggests that it was not. The tail had horizontal fins and a dorsal fin; all three of these fins were triangular.

The Tully Monster had a long proboscis. At the end was a jaw that contained eight small, sharp teeth. There is no evidence that the throat went down the proboscis. It seems more likely that the proboscis was a muscular organ used to pass food to the mouth. Near the middle of the body was a transverse bar that passed through the body. The bar had swellings on the end. These may have been the animal's sensory organs. Scientists do not know to what other animals the Tully Monster is related. Some scientists have speculated that it is related to snails and other molluscs.

The Tully Monster was first found by Mr. Francis Tully in 1958. He took the specimens to the Field Museum of Natural History in Chicago. The specimen defied identification and became known as the 'Tully Monster.' The name stuck.

The Illinois Compiled Statutes

The law designating the ully Monster as the official Illinois state fossil is found in the Illinois Compiled Statutes, Government, Chapter 5, State Designations Act, Section 60.

GOVERNMENT
CHAPTER 5. GENERAL PROVISIONS.
(5 ILCS 460/) State Designations Act.
(5 ILCS 460/60) (from Ch. 1, par. 2901-60)

(5 ILCS 460/60) (from Ch. 1, par. 2901-60) Sec. 60. State fossil. The fossil Tullimonstrum gregarium is designated the official State fossil of the State of Illinois. (Source: P.A. 87-273.)

Taxonomic Hierarchy: Tully Monster

Kingdom: Animalia
    Subkingdom: Eumetazoa
Unranked: Bilateria
Phylum: incertae sedis
Genus: Tullimonstrum
Species: T. gregarium