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Class Trilobita is an extinct class of marine arthropods distinguished by an exoskeleton, which is divided into three lobes; hence the name tri-lobe-ite. Nine orders are contained within this class. They appeared in the Early Cambrian, diversified, declined rapidly in the Late Palaeozoic, before finally going extinct by the end of the Permian. The order Phacopida arose in the Ordovician and went extinct in the Devonian. This order is subdivided into three morphologically diverse suborders. The origin of this order is uncertain.
Class Trilobita arose when the Schizoramia split into the Arachnomorpha and the Crustaccomorpha, which both arose from the Arthropoda. The cladogram below shows a simplified evolutionary history for Class Trilobita.
Author: Sarah Vinnell
Last updated: 21/11/05
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