Hobbies And Interests
State Fossil
The Tully monster (Tullimonstrum gregarium) was named the Illinois state fossil in 1989. This animal, named after amateur fossil hunter Francis Tully who discovered the creature in 1959, is not only unique to Illinois but apparently is unrelated to any other animal phylum. The fossil remains of this creature were discovered in the Mazon Creek shale deposits in the area where Grundy, Will and Kankakee counties meet. The shale beds contained nodules of the mineral siderite (ironstone) that held fossils of Tully's monster and other Carboniferous plant and animal organisms. The shale beds were first discovered in the 1850s but large areas were exposed in the 20th century by strip mining operations for the coal lying underneath the shale.
Appearance
The Tully monster was a soft-bodied marine invertebrate that averaged about a foot long. Its elongated segmented body resembled a fat cigar, tapered down at both ends. The front end had a long proboscis tipped by a pair of jaw-like pincers studded with eight tiny teeth. An eye on a transverse stalk projected from each side of the body near where the proboscis joined the body. The other end of the body tapered to a tail that had two horizontal triangular rippled fins that are believed to have propelled this animal through the water, and a dorsal fin for steering. The pincers, streamlined shape, widely spaced eyes and apparent swimming ability indicate this animal was a predator that attacked small marine animals like shrimp or jellyfish. Paleontologists differ on whether the proboscis was used to suck vital juices from prey or was used like an elephant's trunk to convey food to a mouth.
Mazon Creek Deposits
The Mazon Creek deposits are renowned among paleontologists for having preserved delicate leaf structures of plants and the structures of soft-bodied animals. Generally, plants decay before they can fossilize, and only the hard shells or bones of animals are normally preserved as fossils. But conditions along the shorelines of Illinois' prehistoric seas apparently were perfect for making fossils, with dead plants and animals buried in mud before scavengers or decay destroyed them.
Other Illinois Fossils
Illinois doesn't have the spectacular dinosaur fossils of the Triassic, Jurassic or Cretaceous Eras. But it has an abundance of Carboniferous Era fossils in the Mazon Creek deposits including giant prehistoric relatives of modern horsetails, ferns, club mosses and ginkoes. All told, more than 400 species of Carboniferous Era plants have been identified. But none are unique to Illinois. The Mazon Creek deposits also have yielded fossil remains of Carboniferous jellyfish, worms, snails, clams, scallops, shrimp, fish, giant insects, millipedes, centipedes, giant spiders, scorpions and horseshoe crabs. Again, none of these fossil animals are unique to Illinois.