Fossil footprints tell stories of ancient life

When we think of fossils, we usually think of bones in a museum. But any evidence of prehistoric life is a fossil, and can tell us about the animals that walked the Earth in ages past.

Like detectives investigating a crime scene, scientists study footprints to learn about the creatures that made them. They may be able to learn:

• the size of the animal's foot
• the structure of the foot (round like an elephant, clawed like a cat, toed like a bird?)
• the length of the animal’s leg (for dinosaurs, roughly four times the length of the foot)
• the length of the body (roughly 10 times the length of the foot)
• the width of the body (from the width of the track way)
• the weight of the animal (from the depth of the footprint)
• how fast the creature was traveling (from the length of its stride)
• how many legs the animal had
• whether it dragged its tail
• whether the animal had claws
• whether it traveled in groups or walked alone
• when the animal lived (by the age of the rocks)
• where the animal lived (by the location of the tracks)
• what environment it preferred (by the type of rock)

In some cases the information may not be exact. But put it all together, and you start to get a pretty good idea of just who made these prints.

Some tracks even tell a story. For instance, the Permichnium footprints end abruptly, leading our curators to conclude it may have become lunch for Laoporus!

How do footprints become fossils?

Most of the time, they don’t. But sometimes, tracks made in soft, wet ground, like sand or mud, will dry out in the sun. If they get covered by another layer of material, they may be preserved. Over time, the layers turn to stone. Then, millions of years later, the top layer erodes, revealing the footprints underneath.

Dinosaur footprints in Utah. Photo courtesy of USGS.