Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Cambrian
Contents
Eon Overview
The Cambrian Explosion
The Burgess Shale Fauna
"Age of Trilobites" and the Cambrian Fauna
Plate Tectonics at the Start of the Paleozoic
Evidence
Ottoia prolifica
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sample
Mollusks
Burgess Shale fossils
Hallucigenia
Trilobites
Cambrian algae
Archaeocyath reef
Wiwaxia
Cambrian rocks
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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The "Age of Trilobites" and the Cambrian Fauna
The most abundant and diverse animals of Cambrian time were the trilobites. Trilobites had long antennae, compound eyes, many jointed legs, and a hard exoskeleton like many of their modern arthropod relatives, such as lobsters, crabs, and insects. The Cambrian is sometimes called the "Age of Trilobites" because of their explosive diversification into all marine environments worldwide. In size, they ranged from a few millimeters (1 mm = 0.25 inches) to 45 centimeters (18 inches).

Following the Cambrian, trilobites remained an abundant and diverse element of Ordovician marine faunas, but other groups of organisms that had been more minor elements of Cambrian faunas diversified dramatically. These include snails, clams, brachiopods, cephalopods, corals, bryozoans, and the now extinct graptolites. This post-Cambrian radiation, the Paleozoic Fauna, would dominate marine life until the end of Permian time.




Overview | The Cambrian Explosion | The Burgess Shale Fauna
The "Age of Trilobites" and the Cambrian Fauna | Tectonics at the Start of the Paleozoic



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