Class Trilobita:

Order Phacopida


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.


Origin of Class Trilobita

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.

Simplified cladogram of the evolution of Class Trilobita


Author: Sarah Vinnell
Last updated: 21/11/05
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Websites produced by students on the MSc Palaeobiology programme in the Department of Earth Sciences at the University of Bristol for academic year 2005-6