The Trilobitomorpha is a subphylum of the Phylum Arthropoda that includes the trilobites. Originally a variety of peculiar forms, mostly from the lower Cambrian, were included as the Class Trilobitoidea. However, the many species—known only from fossils—do not appear to be closely related to the trilobites or, in many cases, to each other either, and are now generally placed in separate subphyla when classified at all.
