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.

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.

locality unknown

Suborder Illaenina

Suborder Harpina

Suborder Trinucleina

Order Phacopida

Suborder Cheirurina

Gabriceraurus sp.

Middle Ordovician
Canada, Ontario, Bowmanville

Pliomera fischeri

Russia, St. Petersburg area

Suborder Phacopina

Dalmanites limuloides

USA, New York, Lockport

Ductina vietnami

China, Hunan

Phacops rana

USA, New York, Geneseo

Suborder Calymenina

Flexicalymene niagarensis

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.