Trilobite Lesson for Kids: Facts & Fossils

Instructor: Diane Sieverson

Diane has taught all subjects at the elementary level, was the principal of a K-8 private school and has a master's degree in Measurement and Evaluation.

Trilobites were animals that lived millions of years ago but are now extinct. Come learn about these animals, who their modern relatives are, what they looked like and some other cool facts about them.

What Are Trilobites?

Imagine jumping into a time machine today and going back about 520 million years. When you get out, you find yourself swimming deep in the ocean, near the bottom. There are a lot of interesting creatures you've never seen before, but one catches your attention. It looks kind of like a big, alien bug with two antennae, but instead of crawling around on land it's shuffling along the sandy bottom of the ocean. You're looking at a trilobite!

Trilobite fossil
Trilobite fossil

A trilobite (pronounced TRY-low-bite) is a kind of animal called an arthropod, which has a hard outer casing, legs with joints and a body made up of separate sections. And although trilobites became extinct about 250 million years ago, you're probably familiar with some of their current arthropod relatives, including spiders, scorpions, lobsters, millipedes and insects like the praying mantis.

Tri means 'three', and trilobites got their name from the three long sections of their bodies. Scientists think there were about 20,000 different kinds of them, and their fossils have been discovered on every single continent.

What Were Trilobites Like?

Since trilobites are extinct, we can only look at their fossils, or hardened, preserved remains, to learn more about them. The biggest trilobite fossil known to scientists is about 28 inches long, which is around the same length as four-and-a-half one dollar bills lined up end to end. The smallest was less than half an inch long.

There were thousands of different kinds of trilobites.
There were thousands of different kinds of trilobites

As a trilobite grew, it shed its hard outer casing or exoskeleton for a new, bigger one. A lot of the fossils we have today are those exoskeletons that were shed and then left behind, not the actual animal.

Some trilobites had exoskeletons with long spikes; these probably helped to protect them from other animals that thought they looked like yummy snacks. Others could curl up, like roly-poly bugs, using their hard exoskeletons to protect them from danger!

And though you probably have pretty good eyesight, you only have one lens in each eye. Trilobites were the first kind of life form to have complex eyes. Some even had hundreds of lenses that made up each eye, like the ants we see today, which are also arthropods.

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