Paleozoic Era

The Paleozoic Era is a geologic era that lasted from about 541 to 252 million years ago. It is often referred to as the "Age of Invertebrates" because it was a time when many diverse forms of invertebrate life evolved. The Paleozoic Era is divided into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian.

Cambrian Period (541-485 million years ago)

During the Cambrian period, life exploded in diversity, with the appearance of many major groups of animals, including the first vertebrates and the first complex multicellular organisms.
Key events: Cambrian Explosion, first appearance of trilobites, brachiopods, and mollusks.

Ordovician Period (485-444 million years ago)

Continued diversification of marine life, including the appearance of the first fish and the first land plants.
Key events: Radiation of marine life, first land plants, first fish.

Silurian Period (444-419 million years ago)

Continued diversification of marine life, including the appearance of early jawed fish.
Key events: First jawed fish, colonization of land by plants and arthropods.

Devonian Period (419-359 million years ago)

Referred to as the "Age of Fishes," the Devonian saw the evolution and diversification of many types of fish, as well as the first forests and the first tetrapods (four-limbed vertebrates).
Key events: Diversification of fish, first forests, first tetrapods.

Carboniferous Period (359-299 million years ago)

Characterized by the formation of extensive coal swamps and the rise of large amphibians and early reptiles.
Key events: Formation of coal deposits, diversification of amphibians and early reptiles.

Permian Period (299-252 million years ago)

The last period of the Paleozoic Era, marked by the diversification of reptiles and the appearance of the first true mammals and the first flying vertebrates.
Key events: Diversification of reptiles, first true mammals, first flying vertebrates.

Study Guide

What was the "Age of Invertebrates"?
List the six periods of the Paleozoic Era in chronological order.
What major groups of animals appeared during the Cambrian period?
Which period saw the first colonization of land by plants and arthropods?
Why is the Devonian period referred to as the "Age of Fishes"?
What characterized the Carboniferous period in terms of geological formations and the rise of certain animal groups?
What significant events marked the Permian period?