Earliest trilobites

The earliest-known trilobites are fossils dating back 540–520 million years ago to the early Cambrian, and include such species as Hupetina antiqua from Morocco, Serrania gordaensis from Spain, various species of the genus Fritzaspis from the western USA, and Profallotaspis jakutensis from Siberia, Russia. The trilobite lineage is thought to have originated in Siberia, but gradually radiated outwards until it became globally distributed in marine waters.

Trilobites were an immensely successful, morphologically diverse taxonomic class (and subphylum) of arthropods for many millions of years, and their fossils are readily recognizable by way of their characteristic three-lobed morphology, from which their name, "trilobite" ("three-lobed"), is derived. However, their numbers and diversity began to decline during the Devonian Period, with the last few species dying out during the mass extinction at the end of the Permian Period, around 250 million years ago.