Cambrian Period

The Cambrian Period is the first period of the Paleozoic Era spanning from approximately 540 to 500 million years ago. It was named in 1835 by the geologist Adam Sedqwick, after the region of Cambria in Southern Wales and England, where rocks of this age were first found. The name "Cambria" is a version of Cumbria, which is a latinisation of the Welsh word "Cymry" meaning countryman, or compatriot against the invading Anglo-Saxon tribes. The Cambrian period was a time of "evolutionary experimentation" and adaptive radiation, during which many body plans were tested, but only a few succeeded following natural selection events such as predation, competition, etc.

Events Marking Beginning and End of the Cambrian period

Beginning marked at approximately 540 Mya, Scientists believe that there was:

End was marked at approximately:

Climate and Ecological Communities



Continental drift

Continental Locations - Late Cambrian Period (514 Ma)

Extinction Events

Two Hypotheses for the effect glaciating could have had on existing organisms are:

1) Evidence of continental glaciating at the Cambrian-Ordovician boundary is hypothesized to be responsible for a decrease in climatic temperatures. It is speculated that glaciers would have:

2) The second hypothesis is that the:

Fossil Record

Rocks of Cambrian age are distributed in the Great Basin (the largest desert in the US) of the western United States, parts of the northeastern United States, Wales, Scandinavia and the Baltic region, Siberia, and China, among other places. These localities were not where they are now: the position of the continents was very different (see Continental Drift).

Burgess Shale Formations

The major authorities in primary literature on this geologic period:

Adaptive Radiation

At the beginning of the Cambrian period, about 570 million years ago,

Possible explanations for the Cambrian Explosion are:

I) Animal Diversity:

A) Hard-bodied

Trilobite fossil 1Trilobite fossil 2

B) Soft-bodied

C) Gastropods

D) Other Forms

II) Microbial Diversity

III) Plant / Algal Diversity

Glossary of terms

Adaptive radiation ­
The spread and diversification of organisms into newly opened ecological niches
Brachiopods -
A group of clam-like marine invertebrates separated into two categories based on shell morphology - Geologic Range: Cambrian to Recent.
Burgess Shale ­
Deposits of fine particulate sediment - dated to 520- 515 Mya ­ Large deposits near Alberta and British Columbia ­ First discovered by Charles D Walcott Probably the most famous type of fossil containing rock for this period.
Cambrian Explosion ­
Large "explosion" or radiation that gave rise to a seemingly spontaneous origin for a large majority of the Earthıs genera.
Chitin ­
Nitrogenous-sugar polymers comprising a hard exoskeleton.
Proterozoic ­
Division of the Precambrian eon from 2.5 to 0.56 Ga.
Rodinia ­
Late Proterozoic supercontinent.
Trilobites -
Marine arthropods with a chitinous or calcareous exoskeleton. Geologic Range: Cambrian to Permian.

Literature Cited: