Fossils are the preserved remains of deceased animals in rock. Those found throughout Wisconsin formed from creatures that lived in the warm, shallow seas that once covered the state.
The text and illustrations on these webpages were adapted from Common Paleozoic Fossils of Wisconsin by Ross H. Nehm and Bryan E. Bemis (2002). Photos were generously provided by the Milwaukee Public Museum unless otherwise noted.
Wisconsin fossil fundamentals
Types of Wisconsin fossils
Wisconsin is home to a rich variety of fossils. Visit the pages below to learn more about each type.
These layered and domed fossils formed from mounds of algae about 3 billion years ago.
Bivalves are aquatic mollusks that possess two valves that protect the soft body parts.
Gastropod mollusks: Snails
Gastropods are the most abundant mollusks: There are approximately 40,000 living species and 50,000 fossil species.
Cephalopod mollusks: Squid and octopus
Cephalopods are a group of swimming mollusks, including the living squid, octopus, and the chambered Nautilus.
Trace fossils are the preserved paths of animals that crawled on and bored or burrowed into the seafloor.
There are a variety of rare and little-known fossils that have been found in Wisconsin.