Silurian Reef Fossils
A warm, shallow, tropical sea covered the Chicago area 420 million years ago. During this time tropical reefs flourished and many marine animals lived here. These once living animals are preserved as fossils in the bedrock (mostly dolostone) around Chicago. Field Museum geologists have been collecting these fossils since the museum was founded over 100 years ago. There are over 4,000 specimen lots in the fossil invertebrate collection. The following photos represent just a few of the many thousands of specimens in the collection. Note: The yellow scale bar in each photo represents one centimeter.