Period· The columns of time

Permian

299 Ma → 252 Ma

The period of a single continent, when the relatives of mammals ruled the land, closed by the worst extinction in the history of life.

What the evidence shows

Pangaea is assembled, and its interior lies a thousand kilometres from any coast, so almost no rain reaches it: the middle of the world is desert. For some twenty million years the large land animals are synapsids, the branch that mammals come from, tusked dicynodont herbivores moving in herds and sabre-toothed gorgonopsians hunting them, and whole basins in South Africa and Zambia are made of their bones. It ends twice. Around 262 to 259 million years ago an enormous volcanic province erupts through what is now South China, and the shallow tropical seas lose their large foraminifera and their lime-secreting algae. Then, at 252 million years, volcanoes in Siberia burn through coal beds and vent carbon for perhaps a million years: the sea warms, loses its oxygen and turns acid, and something like nine marine species in ten die.

Bounds and conventions

Its top is among the most precisely dated boundaries in the Phanerozoic, the extinction interval bracketed to within a few tens of thousands of years by uranium and lead in volcanic ash. The proportion of species lost, on the other hand, is an estimate drawn from the fossil record of shelly marine animals and carries a wide margin, and how much of the dying to lay on warming, on the loss of oxygen and on acidification is still being weighed.

Sources

1. Cohen, K. M., Finney, S. C., Gibbard, P. L., Fan, J.-X. (2013). The ICS International Chronostratigraphic Chart. Episodes 36(3), 199–204, mise à jour continue, voir Cohen et al. (2025), Episodes.
2. Shen et al. (2011), Science · Calibrating the end-Permian mass extinction
3. Burgess et al. (2014), PNAS · High-precision timeline for Earth's most severe extinction
4. Penn et al. (2018), Science · Temperature-dependent hypoxia explains biogeography and severity of end-Permian marine mass extinction
5. Wignall et al. (2009), Science · Volcanism, mass extinction, and carbon isotope fluctuations in the Middle Permian of China
6. Kammerer et al. (2022), Journal of African Earth Sciences · The earliest gorgonopsians from the Karoo Basin of South Africa