Fossils of Wisconsin

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.

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.

A slab of gray rock that has been cut to show its layers.

Bivalve mollusks

Bivalves are aquatic mollusks that possess two valves that protect the soft body parts.

Side view of a bivalve mollusk fossil

Gastropod mollusks: Snails

Gastropods are the most abundant mollusks: There are approximately 40,000 living species and 50,000 fossil species.

A circular whorled snail shell fossil

Cephalopod mollusks: Squid and octopus

Cephalopods are a group of swimming mollusks, including the living squid, octopus, and the chambered Nautilus.

A cephalopod mold fossil with visible shell chambers

Trace fossils

Trace fossils are the preserved paths of animals that crawled on and bored or burrowed into the seafloor.

A large stone with several fossilized animal trails

Miscellaneous fossils

There are a variety of rare and little-known fossils that have been found in Wisconsin.

Seven drawings of assorted types of fossils found in Wisconsin