Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
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The Triassic
Extinction and Recovery
Origin of Mammals
Origin of the Dinosaurs
Climate and Plate Tectonics
Skull of Coelophysis
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Skull of Cynognathus
Skull of Buettneria
Bennettitalean 1
Bennettitalean 2
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Climate and Plate Tectonics
Pangea was maximally developed at the start of the Triassic, with Panthalassia (“all ocean”) occupying the other side of the globe, and the Tethys Ocean forming an enormous gulf on the eastern margin of Pangea. Even as the assembly of Pangea was completed, however, it began to rift apart. By the end of the Triassic, rifting in the center of Pangea had begun. North America began to pull away from Europe and Africa, and blocks of crust sank to create rift valleys. During the Late Triassic and Early Jurassic, these valleys were associated with the initial formation of the Atlantic Ocean. The sediments that filled these rift valleys are preserved along the eastern margin of North America and the western edges of Africa and Europe, and they contain important evidence of Late Triassic organisms and their environments.

Early Triassic climate was quite similar to that at the end of the Permian. Much of Pangea was warm and dry, and the interior of this supercontinent was particularly arid. These environments were often dominated by conifers and other gymnosperms. However, the Triassic also saw an increase in seasonality, as well as prominent monsoon weather cycles. Provincial biotas developed as well. In the north (Laurasia), these ecosystems included ginkgoes, bennettitalians, cycads, and tree ferns. In contrast, southern (Gondwanan) environments were dominated by seed ferns, most prominently one called Dicroidium.


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