Triassic

The early Triassic was a time of ecological recovery after the mass extinction that ended the Permian. Life was slow to rebound, but by the middle Triassic, ecosystems had begun to stabilize. Reptiles diversified and filled many of the ecological niches vacated by the extinction, leading to the evolution of early dinosaurs, marine reptiles like ichthyosaurs and plesiosaurs, and the first pterosaurs (flying reptiles).

Amphibians were still abundant during the Triassic, particularly large, crocodile-like species. However, the true evolutionary stars of the period were the reptiles. The therapsids, a group of “mammal-like reptiles,” gave rise to the first true mammals during this time, although these early mammals were small, nocturnal creatures that did not compete with the dominant reptiles.

The Earth’s continents were still fused into the supercontinent Pangaea, and as the Triassic progressed, the first signs of its breakup appeared. This breakup would continue into the Jurassic and Cretaceous periods, gradually shaping the modern continents. The climate was generally hot and dry, particularly in the interior regions of Pangaea, where vast deserts stretched across much of the supercontinent.

The Triassic ended with the Triassic-Jurassic extinction event, around 201 million years ago, which wiped out many large amphibians and reptiles, allowing dinosaurs to dominate the Earth during the Jurassic period.