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Our luxury planet, teeming with life, developed slowly through billions of years. The changes were made in pulses, such as the rise and fall of mountains and sea level. The pauses between these dramatic changes divide the long story in five eras, each lasting hundreds of millions of years. The series of events in each era are divided into periods, each lasting ten of millions of years.

The Devonian Period is the third chapter in the Paleozoic Era of earth’s history. It began quietly some 300 million years ago and lasted 60 million years. In North America, the lofty mountains of the west and the east were still unborn. There were young mountains and volcanos in Alaska and along the north eastern shores and, as the period closed the northern arm of the Appalachians started to poke up its head.

Slowly, slowly the sea invaded the flat central area and then retreated. Vast beds of sedimentary rocks were formed by weathering and the retreating water, Much of New York was buried under muddy deltas washed down from the growing mountain slopes.

The Devonian Period was the Age of Fishes, for the seas teemed with life. There were hordes of ammonoids, the remote ancestors of the octopus. They left fossils of their flat, spiral shells, some three feet wide. There were corals and brachiopods, soft bodied bivalves somewhat like our clams. And there was a vast variety of backboned fishes, large and wall.

Life on land was still sparse, but in this period the soil and chemicals were prepared for the teeming land life which was to follow, When the period started, a few feeble plants were already established on land and the ancestors of the scorpion had left their watery cradle to join them.

When the Devonian Period ended, the Mississippi Valley and other areas were clothed with the earths first forests. The trees were giant ferns and horsetails 40 feet tall, ginkgos and ancient conifers with trunks five feet wide. There were prickly shrubs, velvety mosses and trailing club mosses. The plants provided oxygen and food for animals. The bold scorpions were joined by air .breathing scorpions.

Amphibians left the seas and became the first backboned animals to venture onto the land.

The long eras of earth’s history are named for the type of life they supported. The Paleozoic Era, meaning old life, lasted almost 400 million years. Many of the periods are named for localities. The Devonian Period is named for the English county of Devon where the rocky layers of this geological chapter were first discovered.

 

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