Trilobite << TRY luh byt >> was a prehistoric sea animal. It lived throughout the Paleozoic Era, which lasted from about 540 million years ago to 250 million years ago. Trilobites lived in all parts of the world, and scientists have identified over 10,000 species from fossils.
A soft shell covered much of a trilobite’s body. Most trilobites were under 4 inches (10 centimeters) long. Two grooves divided the animal’s shell lengthwise into three lobes (sections). The name trilobite means three lobes. The body had three main parts: the head, the thorax, and the tail. The thorax had many segments, each bearing legs. The trilobite breathed through gills on the legs.
Although they were the most diverse and widespread animals of the Paleozoic Era, trilobites have no living descendants. Trilobites and most other types of Paleozoic life disappeared completely during a sudden event called the Permian extinction. Scientists believe this event was the most devastating extinction in Earth’s history.
