Paleontology in Illinois
Illinois has a reputation for rocks bearing large numbers of trilobite fossils, often of very high preservational quality.
At the time the state was home to creatures like giant beavers, mammoths, mastodons, and stag mooses.
Paleontology has a long history in the State of Illinois, stretching at least as far back as the 1850s, when the first Mazon Creek fossils were being found.
Early in the ensuing 20th century a Silurian age fossil reef system was discovered in the state.
The Pennsylvanian species Tullimonstrum gregarium ("Tully Monster") is the Illinois state fossil.
Over time this sea would be inhabited by animals like brachiopods, clams, corals, crinoids, snails, sponges, trilobites.
[3] 500 million years ago, during the Cambrian, the seas of Illinois resembled those of the modern Bahamas.
[1] In other areas of Illinois Cambrian trilobite fossils have only been found in core samples drilled from deeply buried rocks.
Most of the state's cystoid fossils are preserved in deposits that formed in that place and time[7] Jaws left by marine worms are even more common from the Silurian of northeastern Illinois than they were back in the Ordovician.
[7] Illinoisan trilobites diversity and abundance suffered further losses after the end of the Silurian Period.
[7] Other inhabitants included the Tully monster, as well as animals recognizably related to modern life like shrimp, jelly fish, sharks and squid.
The fossils they left behind include casts, molds, compressions, and even entire plant preserved in nodules.
[11] Some early vertebrates preserved in the Mazon Creek's concretionary nodules have fossilized soft tissue.
[2] However, one notable local event following the Pennsylvanian was the meteor impact that occurred near modern Des Plaines.
[2] [14][15][16] Likewise, there are few rocks dating back to the ensuing Tertiary period of the Cenozoic era.
[10] The area where modern Peoria is situated was home to the Mississippi river two million years ago.
At the same time, the area where the modern University of Illinois Urbana-Champaign stands was home to the Mahomet River.
[18] The melting glaciers transported large amounts of sediment that filled in the original course of the Mississippi River, which took on its modern course.
During cold spells Illinois was home to animals like mammoths, mastodons, stag mooses, and giant beavers.
Early in the 20th century, J. H. Bretz and H. A. Lowenstam studied the Silurian fossil reef systems of the Chicago area following a decline in scientific attention paid to the famous fossil reefs of similar age near Milwaukee, Wisconsin.
[21] Later, during the 1920s, strip mining for coal south of Braidwood generated piles of waste rock that would later become popular sites for fossil collection.
In 1966, Eugene Richardson, the Curator of Fossil Invertebrates of the Field Museum formally named the Tully monster Tullimonstrum gregarium.
[23] Finally, in 2016, scientists after reviewing over 1,000 fossilized Tully Monsters placed it in the same phylum as, and possibly related to, lampreys.
