TrilobitesTrilobites

Trilobites are an extinct taxon of marine arthropods. Their fossilized exoskeletons are widely dispersed geographically, and there are approximately 5000 known genera of trilobites. Earliest trilobite fossils are dated 540 to 520 million years ago. The name means "three lobes," and refers to the three longitudinal lobes their bodies may be divided into.