Trilobita is an extinct class of marine arthropods that thrived during the Paleozoic Era, approximately 521 to 252 million years ago. They are characterized by their three-lobed body structure, which includes a central axial lobe and two pleural lobes on either side. Trilobites varied in size and shape, with some species reaching lengths of over 70 centimeters. These creatures inhabited various marine environments and were among the first animals to develop complex eyes. Fossils of trilobites are commonly found, providing valuable insights into early life on Earth and the evolution of marine ecosystems.