When the Triassic Period began, all of the major continents of the world were joined into a single colossal opportunity to migrate back and forth from continent to continent. Pangaea was surrounded by Pan-thalassa, the ancestral Pacific Ocean, and was composed of two landmasses: Laurasia in the north, and Gondwana in the south. A narrow bay of the Tethys Sea, comparable to the present Mediterranean, lay between Indo-Africa and Eurasia. Today, the former position of the Tethys is marked roughly by the Alpine-Himalayan mountain belt. One of the most remarkable features of the Triassic was the widespread emergence of continents and the subsequent recession of seas from the continents, as well as the extensive spread of nonmarine deposits, composed largely of redbeds. These redbeds were deposited in a complex river-deltaic-lake system in many parts of the world. Today, they are known from India, Argentina, Brazil, South Africa, East Africa, Germany, Great Britain, China, the United States, and Canada, and have produced a rich record of Triassic vertebrate fauna.
The unity of Pangaea was short-lived. At the end of the Triassic, Pangaea began to break apart, and the continents ultimately shifted to their present positions on the globe. During this initial fragmentation, a rift was opened in the southwest Indian Ocean, moving South America and Africa away from Antarc-
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