Cambrian–Ordovician extinction events

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K-T

Tr-J

P-Tr

Late D

O-S

Millions of years ago

Marine extinction intensity through time. The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized. The labels of the "Big Five" extinction events are clickable hyperlinks; see Extinction event for more details. (source and image info)

The Cambrian–Ordovician extinction event occurred approximately 488 million years ago. It was the first major extinction event in the Phanerozoic eon and it eliminated many brachiopods and conodonts, and severely reduced the number of trilobite species. The Cambrian–Ordovician event ended the Cambrian period, and led into the Ordovician period in the Paleozoic era.

[edit] Theories of Cambrian-Ordovician extinction event

• Glaciation
• Depletion of oxygen in marine waters

[edit] See also

• Geologic time scale
• Furongian
• Early Ordovician

[edit] Further reading

• Gradstein, Felix, James Ogg, and Alan Smith, eds., 2004. A Geologic Time Scale 2004 (Cambridge University Press).
• Hallam, A. and Paul B. Wignall, 1997. Mass extinctions and their aftermath (Oxford University Press).
• Webby, Barry D. and Mary L. Droser, eds., 2004. The Great Ordovician Biodiversification Event (Columbia University Press).

[edit] External links

• Early Ordovician Climate