Trilobites are an extinct group of marine arthropods that lived during the Paleozoic Era, known for their distinctive three-lobed, three-segmented body plan. They are significant in paleontology for understanding the evolution of early life, the diversity of ancient marine ecosystems, and the use of fossils in biostratigraphy.
Reference: Fortey, R. A. (2000). “Trilobite! Eyewitness to Evolution.” Vintage Books.