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How did the Permian mass extinction affect life at the start of the Triassic?
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Triassic Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Triassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The Permian mass extinction, the most extensive in Earth's history, profoundly shaped the biological landscape at the start of the Triassic Period. By the end of the Permian, approximately 85 to 95 percent of marine invertebrate species had vanished, and terrestrial life faced significant reductions in diversity, with only 30 percent of terrestrial vertebrate genera surviving into the Triassic.12
This crisis fundamentally altered the composition of life:
- Marine Ecosystems: Many dominant Paleozoic groups, such as trilobites, rugose and tabulate corals, and blastoids, went extinct. While ammonoids suffered a drastic reduction, the few surviving genera provided the foundation for an explosive adaptive radiation later in the Triassic.132
- Terrestrial Life: Plants and four-legged vertebrates experienced significant declines. During the subsequent recovery, reptiles increased in both number and diversity, eventually leading to the appearance of the first dinosaurs.1
The extinction is often attributed to disruptive environmental changes, such as oceanic anoxia and climatic shifts, which devastated ecosystems and cleared the way for the evolutionary changes that characterized the Mesozoic Era.41