About 252 million years ago

The end-Permian extinction

Earth’s most severe extinction. Volcanic heat released vast amounts of greenhouse gas, and the aftermath lasted a very long time.

Deep history See it on the atlas

What happened

At the end of the Permian period, enormous volcanic activity in what is now Siberia coincided with the largest known collapse of life on Earth, on land and in the sea.

What the evidence shows

The extinction began when the Siberian Traps shifted from mainly surface lava flows to sheets of magma intruding into sediments. Heat from those sills probably released the huge volumes of greenhouse gas that drove the crisis.
In the Early Triassic aftermath, many animals in southern Africa dug burrows. One burrow preserves Thrinaxodon, a small animal of the mammal line, curled up beside an injured amphibian.

What is uncertain

That Thrinaxodon was dormant is an interpretation, based on its curled posture.
The burrow comes from after the extinction. It is not evidence that our own ancestor survived the boundary in a burrow.

Sources

Burgess, Muirhead & Bowring 2017. Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction. Nature Communications. (opens the publisher’s site)
What it supports: The timing of Siberian Traps magma intruding into sediments, a proposed trigger for massive greenhouse-gas release at the start of the end-Permian extinction.
Fernandez et al. 2013. Synchrotron reveals Early Triassic odd couple: injured amphibian and aestivating therapsid share burrow. PLOS ONE. (opens the publisher’s site)
What it supports: A Thrinaxodon, a mammal-line animal, curled in a burrow from the harsh Early Triassic aftermath of the extinction. The dormancy is an interpretation.

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