Geologic Time Scales
Dating 544-245mya, the Paleozoic Era, as all Eras, began and ended with a vast change in the nature of life on Earth. Beginning with the "Cambrian Explosion", the Paleozoic ending was marked by just as an abrupt change in Earth's diversity, a vast extinction of most of those forms of life, called The Great Dying, due to a comet or metor crashing into Earth. The Cambrian Explosion was latter seen to be less of a sudden increase in families, and marked more by extraordinarily good conditions for the formation of fossils. Still, during this period when trilobites, Earth saw its first great experiments in life. Trilobites saw with eyes as advanced as those with which we humble humans see today, yet made with very different materials. The advent of the Predator, totally changing the interactions that ruled animals. Animals that crawled, burrowed, and swam moved within these early, shallow seas.
The Paleozoic is divided into five periods, the Cambrian, Ordovician, Silurian, Devonian, and Carboniferous periods.