Period· The columns of time

Permian

299 Ma → 252 Ma

The Permian, from 299 to 252 million years ago, was the period of the single continent, dominated on land by the close relatives of mammals, and it closed with the most severe extinction in the history of life.

Period of the single continent, dominated on land by the near relatives of mammals, and closed by the most severe extinction in the history of life.

What the evidence shows

Pangaea is assembled, and its interior lies a thousand kilometres from any coast, a distance exceeding the reach of oceanic rainfall: the centre of the continent is desert. For some twenty million years the large land animals are synapsids, the branch from which mammals proceed: tusked dicynodont herbivores living in herds, sabre-toothed gorgonopsians hunting them. Whole basins in South Africa and Zambia consist of their bones. The period ends in two stages. Between 262 and 259 million years, the Emeishan Traps erupt across what is now South China and the shallow tropical seas lose their large foraminifera and calcareous algae. Then, at 252 million years, the Siberian Traps pass through coal beds and vent their carbon for perhaps a million years: the sea warms, loses its oxygen and acidifies, and some nine marine species in ten disappear.

Bounds and conventions

Its top is among the best dated limits in the Phanerozoic: the extinction interval is bracketed to within a few tens of thousands of years by uranium-lead dating of volcanic ash. The proportion of species lost is by contrast an estimate drawn from the record of shelled marine animals and carries a substantial margin; the respective contributions of warming, deoxygenation and acidification remain to be established.