The Paleozoic Era: Definition, Timeline & Events

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  • 0:00 What Was the Paleozoic Era?
  • 0:55 The Cambrian Explosion
  • 1:38 Trilobites
  • 2:09 Tectonics & The…
  • 3:04 Lesson Summary
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Lesson Transcript
Instructor: Jeff Fennell

Jeff has a master's in engineering and has taught Earth science both domestically and internationally.

The Paleozoic Era spans almost 200 million years from 542 to 251 million years ago. It is defined by great explosion of life at the beginning of the era and ends with the largest mass extinction in the history of our planet. This lesson will cover the important features of Paleozoic Era.

What Was The Paleozoic Era?

The Paleozoic Era started 542 million years ago with the emergence of complex life forms and ended 251 million years ago with the largest mass extinction the world has ever experienced. It is the oldest and longest era of the Phanerozoic Eon. The era is usually broken down even further to six main periods:

  • Cambrian: 542 to 488.3 million years ago
  • Ordovician: 488.3 to 443.7 million years ago
  • Silurian: 443.7 to 416 million years ago
  • Devonian: 416 to 359.2 million years ago
  • Carboniferous: 359.2 to 299 million years ago
  • Permian: 299 to 251 million years ago

The Cambrian Explosion

542 million years ago, simple life forms were thriving in the ocean environments, but the continents were still void of life. The Paleozoic Era would see an explosion of variety of diverse life forms in the ocean and eventually make the leap onto land. This rapid growth of diversity in animals is known as the Cambrian Explosion. By the Silurian Period, both plants and invertebrate animals had made their way onto land. Vertebrate fish had ventured out of the sea and become land dwellers by the Devonian Period. Once on land, life became as diverse as the sea. The Carboniferous Period saw the emergence of flight with winged insects.


Probably the most successful animal during the Paleozoic Era was the trilobite. A small arthropod, trilobites averaged in size between 1 and 4 inches. Trilobite fossils have been found worldwide in marine rocks, suggesting they never made the transition to land. Although now extinct, there were roughly 17,000 species of trilobites during their peak. Their abundance and variety in the fossil record have made trilobites important and useful in studying Earth's history.

Plate Tectonics and the Permian Extinction

Through most of the Paleozoic, there were a number of continents across the globe. By the end of the era, the continents had recombined to form the most recent supercontinent, Pangaea.

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