Ordovician

The Ordovician is the second period of the Paleozoic era and the Phanerozoic eon. It lasted from about 485.4 million years ago (mya) to 443.4 mya.^[1] It follows the Cambrian period and is followed by the Silurian period.

The Ordovician was named after the Welsh tribe of the Ordovices. It was defined by Charles Lapworth in 1879. He recognized that the fossils in the disputed strata were different from those of the Cambrian or the Silurian. Therefore, he reasoned, they should be placed in a period of their own.

Recognition of the Ordovician period was slow in Britain, but elsewhere it was quickly accepted. In 1906 it was adopted as an official period of the Paleozoic era by the International Geological Congress.

The Ordovician ended with a series of extinction events that, together amount to the second greatest extinction of the Phanerozoic. This was the End–Ordovician extinction event.

1. ↑ Gradstein, Felix M; Ogg J.G. & Smith A.G. 2004. A geologic time scale 2004. Cambridge: Cambridge University Press. ISBN 0-521-78673-8