Introduction to the Polymerida

The Polymerida, which make up 95% of all trilobites, are the trilobites that most people are familiar with. Unlike the agnostids, polymerid trilobites typically have more than two or three thoracic segments, and the pygidium is usually smaller than the cephalon. Unlike the blind agnostids, most polymerid trilobites had remarkably well-developed compound eyes. (A few, like Ductina, were blind, but this was a secondary evolutionary development.) Polymerid trilobites appear in the Early Cambrian Period, and the last ones went extinct at the end of the Permian.

There is currently no consensus as to how the major groups of polymerid trilobites are related to each other. In fact, it is possible that the group is paraphyletic; the last common ancestor of all polymerid trilobites may also have been ancestral to the agnostids as well.

The text below presents the polymerid trilobites as they are traditionally classified, with no evolutionary relationships indicated. For the moment, click on any of these in-line pictures for a full picture, to get an idea of trilobite diversity.

Order Redlichiida
			Suborder Redlichiina		Bergeroniellus spinosus Early Cambrian Siberia, Lena River
					Paradoxites sp. Cambrian Czechoslovakia, Jince Beds
			Suborder Olenellina		Nevadella sp. Early Cambrian USA, Nevada, Silver Peak Range
Order Corynexochiida
					Olenoides serratus Middle Cambrian Canada, British Columbia, Mt. Stephen
					Ogygiocarella debuchii Middle Ordovician U.K., Wales, Powys
Order Ptychopariida
			Suborder Ptychopariina		Elrathia kingi Middle Cambrian USA, Utah, House Range
			Suborder Asaphina		Megistaspidella sp. Lower Ordovician Russia, St. Petersburg
					Homotelus sp. Ordovician locality unknown
			Suborder Illaenina
			Suborder Harpina
			Suborder Trinucleina
Order Phacopida
			Suborder Cheirurina		Gabriceraurus sp. Middle Ordovician Canada, Ontario, Bowmanville
					Pliomera fischeri Ordovician Russia, St. Petersburg area
			Suborder Phacopina		Dalmanites limuloides Silurian USA, New York, Lockport
					Ductina vietnami Devonian China, Hunan
					Phacops rana Devonian USA, New York, Geneseo
			Suborder Calymenina		Flexicalymene niagarensis Silurian USA, Wisconsin, Milwaukee
Order Lichiida
Order Odontopleurida

We hope to fill in the gaps in this page with more images and more information as time goes on.

For more pictures of trilobites, including some of the most outrageous ever seen, visit Kevin's TRILOBITE home page, maintained by Kevin Brett at the University of Alberta. This excellent page also maintains links to many other trilobite pictures and information.

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