Trilobite

Trilobites were small marine animals that lived in ancient seas hundreds of millions of years ago. They appeared early in the history of life on Earth and existed for a very long time. Trilobites are now extinct, which means no living members remain. Scientists know about them from fossils found in rocks around the world.

Trilobites first appeared during the Cambrian Period, about 520 million years ago. They lived through several geological periods and disappeared at the end of the Permian Period, about 252 million years ago. A geological period is a long span of time in Earth’s history marked by changes in life and environment. Trilobites lived much earlier than dinosaurs.

The body of a trilobite was divided into three main parts. These parts are the head, the middle body, and the tail. The name trilobite means "three lobes" because the body is divided lengthwise into three sections. Many trilobites had hard outer shells made of mineral material. This hard shell helped protect their bodies and is why their fossils are often well preserved.

Trilobites lived on the sea floor. Some crawled along the bottom, while others swam just above it. They likely ate small plants, tiny animals, or bits of organic matter. Organic matter means material that comes from living things. Different species of trilobites had different shapes, which suggests they lived in different ways.

Trilobites had eyes made of calcite, a type of mineral. Some species had large eyes with many lenses, while others had very small eyes or none at all. This suggests that trilobites lived in a range of light conditions, from shallow water to deeper, darker seas. Their eyes are among the oldest known complex eyes in the fossil record.

Today, trilobite fossils are important to scientists. They help show how early animals lived and changed over time. Because trilobites evolved quickly and were widespread, their fossils are also used to help date rock layers. This means scientists can learn the age of rocks by finding which trilobite species are inside them.