Devonian Period, a division of geologic time. It began about 395,000,000 years ago and lasted about 35,000,000 years. It is the fourth period of the Paleozoic Era. The Devonian Period is named after Devonshire, England, where rocks of this period were first studied.

Plants of the period included ferns, large horsetails, and club mosses. Land animals were small creatures such as insects, scorpions, centipedes, and tetrapods. Marine life included shellfish, coral, starfish, barnacles, lobsters, and crabs. Sharks and other large fish were common in lakes as well as oceans. The Devonian Period is sometimes known as the Age of Fishes.

The fossil remains of these plants and animals are found in sandstone, limestone, and slate that were formed during the Devonian Period. These rock formations are close to the surface of the earth in southwestern England, the Ardennes region of France, the mountains near the Rhine River in Germany, the Appalachian Mountains and the north-central United States, and the province of Ontario in Canada, and in Ghana and Bolivia.

Among the valuable products obtained from Devonian rocks are petroleum, natural gas, cement, phosphate, and building stone. The Devonian rocks near the Rhine contain large quantities of iron, tin, and copper.