The Paleozoic Era

The Era of the Ocean

How long?

The Paleozoic Era was approximately 300 million years long. The Paleozoic is divided into six periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Most of these names derive from locations where rocks of these ages were first studied. The Paleozoic is bracketed by two of the most important events in the history of animal life. At its beginning, animals underwent a dramatic change in diversity, and almost all living marine animals appeared within a few millions of years. At the other end of the Paleozoic, the largest mass extinction in history wiped out about 90% of all marine animal species.
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Life in the Paleozoic Era

At the beginning of the Paleozoic, life existed only in or near the ocean. Trilobites, shellfish, corals, and sponges appeared, followed by the first fish. Land plants appeared near the end of the Ordovician and for the first time we see the green of land plants in our global view. Huge forests and swamplands formed during the warm climate of the Mississippian and Pennsylvanian periods that later fossilized into the giant coal beds of the eastern United States. Animal life also moved onto the land, first the arthropods (spiders and insects to you), then the amphibians, and later the reptiles. The most abundant animals on land and sea during the Paleozoic were those like shellfish and insects that lacked backbones, so the Paleozoic is often called "The Age of Invertebrates."


The Paleozoic was a time of extreme evolutionary change and the foundations of life as we know it were set during this period. Right before the Paleozoic, there were few, if any animals with hard shells, and as far as we know, there were no land plants or animalswhatsoever. The largest early Paleozoic animal was probably no more than a few inches in length, as the earlier Ediacaran communities, which consisted of simple frond-like organisms up to a meter or so in length, had mostly died out.

In the Paleozoic Era, life diversified rapidly and fantastically on land and in the ocean. Life in the sea changed drastically during this time. Trilobites, mollusks, urchins, and star fish appeared at the beginning of the Paleozoic as part of the "Cambrian Explosion." Later, jawless fish evolved, then fish with jaws, and even sharks filled the seas by the end of the Paleozoic. Species diversification of vertebrates and invertebrates alike went quite wild, and some fairly bizarre creatures emerged: including an armored fish 30 feet long and many nightmarish-shaped invertebrates

The end of the Paleozoic Era

Pangea was shaped like a large “C.” It surrounded the Tethys Sea. The rest of the Earth was covered by a huge ocean named Panthalassa. Even though the ocean covered much of the earth, Pangea was so large that the interior did not benefit from the ocean waters. Deserts were places in the center of Pangea where the temperatures changed from very cold to very hot. In some places there was rarely or never any rain. Over all the earth was dry during the Permian Period.

The swamp land dried up and many of the plants that needed the water died out. New plants developed that were adapted to the dryer conditions. They were called gymnosperms. These plants had seeds. One of the earliest of these plants still exists today. It is called the Ginkgo. Most of the trees living during the Permian period were conifers. Conifers are trees with seeds in cones.