Which era ends with the Permian-Triassic extinction event?

• A. Mesozoic
• B. Paleozoic
• C. Cenozoic
• D. Precambrian

Answer: (B)

This event marks the boundary between two major intervals in Earth’s history. It ends the Paleozoic era and begins the Mesozoic era. About 252 million years ago, the Permian-Triassic extinction was the largest mass extinction in the planet’s history, wiping out a huge share of species and reshaping ecosystems. Because of that dramatic turnover at the end of the Permian period, we define the end of the Paleozoic as the boundary, with the Triassic starting the Mesozoic. The Paleozoic spans roughly 541 to 252 million years ago and saw major diversification of marine life and the emergence of land vertebrates, ending with this mass extinction. The Mesozoic comes after and lasts until about 66 million years ago, followed by the Cenozoic. The Precambrian lies before the Paleozoic, so it doesn’t fit the boundary described.