Devonian Period
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Early tetrapods Acanthostega
(foreground) and Ichthyostega. Image: PBS
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The fourth oldest of the six periods of the Paleozoic
Era. The Devonian Period spans the time between the Silurian
and the Carboniferous, about 417 to
359 million years ago. During the Devonian, two major animal groups appeared
on land: the first tetrapods, or land-dwelling
vertebrates, and the first terrestrial
arthropods, including wingless insects
and the earliest arachnids. In the oceans,
brachiopods, crinoids
and other echinoderms, tabulate and rugose
corals, and ammonites
flourished, and many new kinds of marine and freshwater fish
appeared, including jawless fish and forerunners of today's fish (the Devonian
is sometimes called the Age of Fishes). The vegetation of the early Devonian
consisted primarily of small plants, the
tallest being only a meter tall. By the end of the Devonian, ferns,
horsetails and seed plants had also appeared,
producing the first trees and the first forests.
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