The Triassic period was the first period of the Mesozoic era, following the Permian-Triassic extinction which wiped out 96% of marine genera and 70% of terrestrial genera. Pangea and Panthalassa dominated the world, with a hot and dry climate. Reptiles thrived on land, while modern corals and ammonites flourished in the oceans. Gymnosperms dominated the forests.
The Triassic period is the first period of the Mesozoic era, which lasted for about 180 million years. Mesozoic means “middle life”, the time between the ancient Paleozoic and the modern Cenozoic. The Triassic itself dates back to about 251-199 million years ago.
The Triassic period marked an unusual time: life was recolonizing the Earth after the largest mass extinction ever, the Permian-Triassic extinction, during which 96% of marine genera were wiped out, 70% of terrestrial genera and 99.5% of individual organisms. The precise cause of the Permian-Triassic extinction is not known, but it was so devastating that biologists informally call it “the great death.”
During the Triassic period, the world was defined by a supercontinent, Pangea, and a supersea, Panthalassa. At the center of Pangea was a gigantic desert, the largest the Earth has ever seen. The general climate was very hot and dry throughout, presenting a challenge for colonization.
In the oceans, modern corals first appeared, resuming the extensive reef-building activities that had ceased during the Silurian nearly 150 million years earlier. Ammonites flourished, diversifying from a single line that had survived the Great Death. A number of fish and reptile-like fish flourished in the sea, including ichthyosaurs, plesiosaurs, and many others. At the end of the Triassic period, some of these, especially the ichthyosaurs, developed to dinosaur proportions. Echinoderms evolved in the seas.
On land, the real winners of the Triassic, as well as all the rest of the Mesozoic, were the reptiles. This is why the Mezoic is often referred to as the “Age of Reptiles”. Truly modern insects, such as dragonflies, first evolved in the Triassic. Among dinosaurs, archosauromorphic (cold-blooded) reptiles thrived the most on their endothermic (warm-blooded, mammal-like) relatives, probably because cold-blooded reptiles were better adapted to arid environments. The great continent Pangea was mostly desert, dotted with oases and a thin ring of coastal life.
The Paleozoic swamp-like trees and ferns that gave rise to the largest coal deposits on Earth needed moisture to thrive and therefore didn’t do so well during the dry Triassic. Evergreens, such as conifers and other gymnosperms, dominated the forests of the Triassic Period.
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