Prehistoric Life in Southern Illinois

Paleocene Foraminifera from the Porters Creek Formation of Southern Illinois

Fossils in Illinois were preserved during times of geologic deposition, roughly from the Cambrian to the Carboniferous Period of the Paleozoic Era (540-323 million years ago) and from the end of the Cretaceous Period (66 million years ago) to modern times. During the time of the dinosaurs from the Permian to the end of the Cretaceous, Illinois was above ground and preserved no fossils.