WGNHS
Wisconsin Geological and Natural History Survey

Trace Fossils

Trace fossils are the preserved paths of animals that crawled on and bored or burrowed into the seafloor. A variety of paths representing behaviors—such as feeding, moving, and resting—can be found in sedimentary rock. Certain burrowing behaviors are specific to certain environments, so paleontologists can reconstruct ancient environments from the shape of trace fossils. Trace fossils are common in the Paleozoic rock of Wisconsin and are still being formed in ocean sediments today.

Three drawings showing different types of trace fossils
Trace fossils. A) Large, worm-like feeding traces parallel to rock layers [as much as 1 cm in diameter]. B) Large, variably shaped borings perpendicular to rock layers [1 cm or more in diameter; 4 cm or more in length]. C) Long, thin burrows perpendicular to rock layers [less than 0.5 cm in diameter; up to 5 cm or more in length].

Trace fossil photos

A rock with worm burrow cast fossils
Worm burrows
A rock with fossilized worm burrows
Worm burrows
A large stone with several fossilized animal trails
Climactichnites trails: these tracks were left by giant slug-like animals
A large stone with a single fossilized animal trail going diagonally across the image
Large Climactichnites trail
A fossilized trilobite burrow
Trilobite burrow
Stone with two fossilized jellyfish impressions
Jellyfish impressions: jellyfish fossils are very rare because their bodies are made of mostly soft material

Learn more about fossils

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The text and illustrations on this page were adapted from Common Paleozoic Fossils of Wisconsin by Ross H. Nehm and Bryan E. Bemis (2002). The photos on this page are by Carol McCartney and Madeleine Haberman.