Devonian << duh VOH nee uhn >> Period was a time in Earth‘s history that lasted from around 419 million to 359 million years ago. The period takes its name from the county of Devon in southwestern England, where rocks of this age were first identified. Other well-known samples of Devonian rock come from the Finger Lakes region of New York and the desert mountains north of Las Vegas.
During the Devonian Period, plants and animals continued to spread onto land. The first tree-sized plants appeared, forming forests that housed the first insects and tetrapods (four-legged animals). These plants and animals probably could not survive far from the damp conditions found along riverbanks and in swamps. Away from such areas, the land most likely remained barren.
Sea creatures also evolved (developed gradually) into new forms during the Devonian Period. The first ammonites appeared. These distant relatives of the squid produced tightly coiled shells. Fossil collectors prize ammonite shells for their beauty. Many new types of fish also evolved during the Devonian Period, including modern-looking sharks and Dunkleosteus, a giant predatory (hunting) fish with an armored skull.
Much of Earth’s land during the Devonian Period formed two large continents. A narrow ocean near the equator separated the two land masses.
