Fossils are evidence of the plants and animals that lived thousands of years ago. Scientists search for them in sedimentary rocks that are found on many continents. In this lesson, we’ll learn about fossils and where various types have been found.

Let’s Dig In

Have you ever left your footprint in the mud and then it hardened? Well, if it were filled with silt or clay and compressed, then it could become a fossil. It would be a trace fossil because the footprint is evidence of animal activity that is preserved.

Trace fossils of dinosaur footprints found in sandstone.
Trace Fossil

Another type of fossil is called a body fossil. It is the remains of a plant or animal that are trapped under dirt and preserved over a long period of time. Much of what scientists know about dinosaurs today is because of the fossils that have been found.

Body fossil of multiple trilobites
Body Fossil

While remains of any age may be found, scientists do not consider remains to be ‘fossils’ unless they are over 10,000 years old – otherwise, it is considered ‘recent.’ ‘Fossil’ comes from the Latin word fossilis, meaning ‘dug up.’ So, let’s dig in to learn more about where fossils are found.

What’s the Dirt on Fossils?

Most fossils are found in sedimentary rock. Sedimentary rock is formed by dirt (sand, silt, or clay) and debris that settles to the bottom of an ocean or lake and compresses for such a long time that it becomes hard as a rock. Limestone and sandstone are types of sedimentary rock that commonly have fossils.

Plants and animals get stuck in the layers of sediment for thousands of years and create fossils. However, the actual plant or animal is not in the fossil. After a plant or animal is under the sediment, minerals harden around the shape of it. Later, water washes away the remains that are left between the layers. What scientists find are the molds of the plants or animals created by the mineral deposits.

For example, in order to find a Tyrannosaurus Rex fossil, you will need to look where there are sedimentary rocks that are 67 million years old because that is when they lived.

What Are Amber Fossils?

Fly inside an amber fossil.
Amber fossil

Although fossils are most commonly found in sedimentary rocks, some fossils have been found in amber. Amber fossils are formed when resin (similar to sap) from trees is preserved with a plant or animal trapped inside it. Most amber fossils contain an insect that was caught in it when the resin was fluid and then later hardened.

Where Have Fossils Been Found?

High desert regions have had many fossil findings. Deserts have very little organic matter covering the ground so it is easier for scientists to find fossils in them. They have been found in many locations in the western part of the United States as well as Argentina and China.

Did You Say Fossil Poop?

Fossil poop is another type of fossil found throughout the world. Its scientific name is coprolite. Scientists study coprolite to see which animal it came from. They have discovered coprolite from many different animals such as dinosaurs, crocodiles, fish, insects, and humans. Many crocodile coprolites have been found in the state of South Carolina. In Wyoming, 50 million year old coprolites have been discovered from fish.

Lesson Summary

The two major types of fossils, which are molds of plants and animals that lived thousands of years ago, are trace fossils and body fossils. They are usually found in sedimentary rock that was formed during the time period they were alive. Fossils have been found on all continents, but mostly in North and South America, and Asia.