Paleozoic

From Palaeos

The Paleozoic Era of the Phanerozoic Eon:

542.0 to 251.0 million years ago

Devonian scene showing acanthodian fish (Kentuckia), rugose and tabulate (Favosites) corals, crinoids (only the stems are visible here), a trilobite and a gastropod

Early in the 300 million year history of the Paleozoic, atmospheric oxygen reached its present levels, generating the ozone shield that screens out ultraviolet radiation and allows complex life to live in the shallows and finally on land. This era witnessed the age of invertebrates, of fish, of tetrapods, and (during the Permian) reptiles. From the Silurian on, life emerged from the sea to colonize the land, and in the later Paleozoic pteridophyte and later gymnospermous plants flourished. The generally mild to tropical conditions with their warm shallow seas were interspersed with Ordovician and Permo-Carboniferous ice ages. Towards the end of the Paleozoic the continents clustered into the supercontinent of Pangea, and increasingly aridity meant the end of the great Carboniferous swamps and their unique flora and fauna. The Paleozoic was brought to an end by the end Permian mass-extinction, perhaps the most severe extinction the planet has seen.

The Paleozoic (also spelt "Palaeozoic") era lasted from about 540 to 250 million years ago, and is divided into six periods The 320-odd million years of the Paleozoic era saw many important events, including the development of most invertebrate groups, life's conquest of land, the evolution of fish, reptiles, insects, and vascular plants, the formation of the supercontinent of Pangea, and no less than two distinct ice ages. The Earth rotated faster than it does today so days were shorter, and the Moon being nearer meant stronger tides.

The six periods, followed by the time they began are:

Permian 299 Mya

Carboniferous 359 Mya

Devonian 416 Mya

Silurian 444 Mya

Ordovician 488 Mya

Cambrian 542 Mya

Palaeos com - Paleozoic

Credits (Paleozoic pages) - Kheper Site MAK980528, Palaeos com MAK020409, checked ATW020714, last modified ATW041219, transferred to Palaeos org MM060921, divided into several pages MAK060923.