High Quality Content by WIKIPEDIA articles Trilobites ( /ˈtraɪləbaɪt/, /ˈtrɪləbaɪt/; meaning "three lobes") are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (526 million years ago), and they flourished throughout the lower Paleozoic era before...