Silurian << suh LOOR ee uhn >> Period was a time in Earth‘s history that lasted from about 444 million to about 419 million years ago. Geologists first identified rocks of this age in the border region between England and Wales. The period takes its name from the Silures, an ancient Celtic tribe that lived in the area. Geologists have also found Silurian Period rocks in many other places, including notable formations in North America and China.
The oceans featured a great diversity of life during the Silurian Period. Primitive sea animals thrived, including trilobites, brachiopods, graptolites, and crinoids. Coral reefs flourished, particularly near the equator. In addition to corals, the reefs housed large, heavy creatures resembling modern sponges.
Also during the Silurian Period, arthropods, such as millipedes, appeared on land for the first time. Land plants during the Silurian Period included mosses and other similar plants. They were short, probably reaching no more than 1 foot (30 centimeters) in height. They also required the damp conditions found along riverbanks and in swamps. Away from such areas, the land remained barren.
In the Silurian Period, most of Earth’s land lay in the Southern Hemisphere, but the land mass that is now North America straddled the equator. As the period progressed, a small continent collided with what is now the eastern edge of North America. Rocks along the collision zone crumpled and uplifted, forming the Appalachian Mountains.
