A trilobite is an extinct marine arthropod that lived during the Paleozoic Era, approximately 521 to 252 million years ago. These creatures are characterized by their three-lobed body structure, which includes a central lobe and two side lobes. Trilobites were diverse and thrived in various marine environments, making them important indicators of geological time. Trilobites had a hard exoskeleton, which helped protect them from predators. They are often found as fossils, providing valuable information about ancient ecosystems. Their unique features and evolutionary history make trilobites a significant subject of study in paleontology, the science of ancient life.