State Fossil of Illinois
Tully Monster (common name) Tullimonstrum gregarium (scientific name) STATUS Official  DESCRIPTION Tullimonstrum gregarium was a prehistoric species of marine invertebrate that lived during the Pennsylvanian epoch of the Carboniferous period, approximately 280 to 320 million years ago. Thought to be an active carnivore, the Tully monster lived in the hot, lowland swamps and shallow seas that once covered Illinois. Today, fossils of this creature are often preserved as compressed outlines. STATE SYMBOL The Mazon Creek area in Grundy and Will counties, Illinois, is important to paleontology because of the abundance of fossils of soft-bodied animals, insects, and plants that occur there. Normally, only hard portions of animals, such as teeth and bones, are fossilized. However, conditions were just right in this unique prehistoric environment, and dead creatures, includingTullimonstrum gregarium, were buried in sediment. Because they were buried quickly, decay and predators did not have a chance to destroy the organisms. These organisms were later cast in the mineral siderite and preserved as fossils. Since the late 1950s, over 100 Tullimonstrum gregarium fossils have been found in these siderite deposits in Illinois. So far, this species is unique to Illinois and has not been found anywhere else in the world. A committee from the Illinois State Geological Survey lobbied the state legislature, and in 1989, a bill passed designating the Tully monster Illinois’ official state fossil. The Mazon Creek area of Illinois is famous for a diverse array of plant and animal fossils. Well-preserved Tully monster fossils from this region are on display at the Illinois State Museum in Springfield and at the Field Museum of Natural History in Chicago. NAME ORIGIN The scientific name for this animal, Tullimonstrum gregarium, honors amateur collector Francis Tully, who first discovered it. The wordgregarium means "common," referring to the fact that the fossil is fairly common at the site where it was found in Illinois. Eugene Richardson, then-curator of fossil invertebrates at the Field Museum of Natural History in Chicago, gave the Tully monster its scientific name in 1966. BIOLOGY/ANATOMY The Tully monster was a marine invertebrate with a segmented body. Individuals normally ranged in size from approximately five inches to 1.5 feet (13 cm to 46 cm) in length. This soft-bodied, flexible animal had no shell and no backbone. The front end of this creature had something similar to a jaw with small teeth and is thought to have had two eyes. Tully monster may have used its teeth to puncture its prey, which perhaps consisted of shrimp and jellyfish. Most likely an active swimmer, Tully monster had three triangular fins: two horizontal fins and one dorsal fin. EVOLUTION/EXTINCTION Scientists do not know what caused the extinction of Tullimonstrum gregarium. MODERN DISCOVERY This invertebrate was named for amateur fossil collector Francis Tully. Tully found the first of this species in 1958. He made his discovery in a mine near Braidwood, Illinois, and took the fossil to the Field Museum of Natural History in Chicago. Since scientists were unable to correctly identify the creature, it was initially given the nickname, "Mr. Tully’s monster," and the name stuck. TRIVIA Scientists are not sure to what modern animals the unique Tully monster is related, but some have suggested snails and other mollusks. This creature has been placed in the pseudo-phylum "Problematica," referring to creatures of uncertain taxonomy.  A common theory among those who believe in the existence of the Loch Ness Monster is that this Scottish marine animal could be a surviving Tully monster.
	Click to enlarge an image Tully Monster Impression CLASSIFICATION Kingdom: Animalia Phylum: Eumetazoa Unranked: Bilateria Phylum: (Problematica) Genus: Tullimonstrum
	Author: World Trade Press