Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Cambrian
Eon Overview
The Cambrian Explosion
The Burgess Shale Fauna
"Age of Trilobites" and the Cambrian Fauna
Plate Tectonics at the Start of the Paleozoic
Ottoia prolifica
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Burgess Shale fossils
Cambrian algae
Archaeocyath reef
Cambrian rocks
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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Cambrian 542 - 488 mya
Defining Characteristics:
  • • Cambrian Explosion
  • • skeletonized animals
  • • early animal diversification
  • • Map of the Cambrian World
Secondary Characteristics:
  • • diversification of trilobites
  • • Burgess Shale fauna
  • • warming climates
  • • Plate tectonics

The Cambrian was first defined by Adam Sedgwick in England (Cumbria) and Wales; Cambria is the Roman name for Wales. Since then, Cambrian-age rocks have been found on every continent; they occur throughout North America, where the Burgess Shale, in British Columbia, Canada, is an especially significant deposit of Middle Cambrian rocks that preserve soft-bodied organisms. Lower Cambrian rocks in Yunnan, China, preserve the famous soft-bodied Chengjiang biota. In Antarctica, Upper Cambrian rocks in the Ellsworth Mountains preserve a highly varied shelly fauna. Cambrian-aged shelly fossils occur widely throughout Australia, Europe, the Lena and Aldan River areas of Siberia, and in North Africa.

Cambrian rocks were deposited between 543 and 490 million years ago, and they are now defined as the first period of the Paleozoic Era; it is at this time that animals having shells (exoskeletons) become widespread in the fossil record. Before the Cambrian, in the late Neoproterozoic Era (often called the Vendian), Earth had multicellular life; however, the organisms were soft bodied. This Vendian soft-bodied biota occurs in the famous Ediacaran beds of South Australia and now has been found in many other parts of the world. Before the Vendian, life was largely represented by single-celled organisms such as Archaea, filamentous microorganisms, algae, and other organisms that are studied by using microscopes.

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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