Cambrian–Ordovician extinction event
The Cambrian–Ordovician extinction event occurred approximately 488 million years ago (m.y.a.). This early Phanerozoic Eon extinction event eliminated many brachiopods and conodonts, and severely reduced the number of trilobite species.
See also 
- End Botomian extinction event, circa 517 m.y.a.
- Dresbachian extinction event, circa 502 m.y.a.
- Geologic time scale
- Furongian, Late or Upper Cambrian period
- Early Ordovician period
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).
Millions of years before present
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