Paleozoic

The Paleozoic Era is the first major division of the Phanerozoic Eon. The term ‘Paleozoic’ means ‘ancient life.’ It is the longest era of the Phanerozoic and is divided into six periods, listed from oldest to youngest: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

The Paleozoic represents a time of remarkable geological, climatic, and evolutionary changes. One of the most notable features of Paleozoic life is the sudden appearance of nearly all major groups of invertebrates in great abundance at the beginning of the Cambrian. The first vertebrates emerged as primitive fishes, which diversified significantly during the Silurian and Devonian periods.

While macroscopic plants first appeared in the early Paleozoic, plants remained mostly aquatic until the Silurian, around 420 million years ago, when they began to colonize land. The first animals to appear on land were arthropods.