Scientists Say: Ichnology

Rather than study organisms themselves, this field looks at marks they left behind

A scientist places her hand alongside a fossilized dinosaur track, an example of a trace fossil.

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Ichnology (noun, “ICK-nawl-uh-jee”)

Ichnology is a branch of science that studies tracks, burrows and materials left behind by living things. These left-behind clues are called traces.

Ichnology doesn’t study the bodies of living things. Nor does it study the fossilized remains of past life, such as bones. Instead, ichnology looks at the way those living things changed their surroundings. Such changes may include tracks through the mud or burrows in sediment.

A scientist who studies traces is called an ichnologist. Many ichnologists study fossilized traces. Fossil traces can tell us about the environment in a particular region when the fossils formed. Trace fossils might tell us whether a region was once a marsh or a deep ocean basin. That’s because different living things inhabit these two places. And they each leave behind their own clues. These clues can tell us about the past water depth, salinity, light level and more.

Other ichnologists study modern traces. This information can help scientists better understand the past as well as the present. Here’s an example. Marine animals, such as clams, live in burrows they dig in the ocean floor. If the environment changes — the temperature cools, or food becomes less available — they may dig a deeper burrow or move to a new spot. We can’t directly measure things like temperature or food availability hundreds of thousands of years ago. But comparing patterns in fossilized burrows with clam burrows today may give us clues about the environment those ancient animals lived in.

Ichnology goes back a long time. Consider the ancient humans who hunted animals by looking at their tracks. They were already using the science of ichnology.

In a sentence

To figure out that the duck-billed dinosaurs called hadrosaurs lived in herds, scientists looked to the field of ichnology and studied fossilized dinosaur tracks.

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Katie Grace Carpenter is a science writer and curriculum developer, with degrees in biology and biogeochemistry. She also writes science fiction and creates science videos. Katie lives in the U.S. but also spends time in Sweden with her husband, who’s a chef.

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