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The birth of a mountain range in what is now South Africa may have helped to drive one of the most severe mass extinctions in Earth鈥檚 history.

The Permian extinction struck about 252 million years ago. It鈥檚 traditionally thought to have wiped out at least 80 per cent of species in the sea and on land. Massive volcanic eruptions are thought to have played a major role.

But in the last five years we have realised that another mass extinction happened not long before, roughly 260 million years ago . Between 75 and 80 percent of all land animals vanished.

It is still poorly understood, but the Capitanian extinction on land seems to have been far worse than the land die-off during the Permian extinction, says at the New Mexico Museum of Natural History. 鈥淭he ecological severity of the extinction of the end-Capitanian dwarfs what happens at the end of the Permian,鈥� he says. 鈥淚 think what we鈥檙e going to find out, and this is my best hunch, is that the really important extinction was the end-Capitanian.鈥�

In other words, the Permian extinction may have been mostly in the sea, with most of the land extinctions happening during the earlier Capitanian event.

The Capitanian event may also have ushered in the Permian disaster. It may have left ecosystems depleted, so life was still vulnerable when the volcanoes began erupting 6 million years later 鈥� helping to explain why the Permian extinction was so severe.

The trouble is, nobody knows what caused the Capitanian extinction.

Now palaeontologist at the University of the Witwatersrand in South Africa and his colleagues have found a clue. They studied the fossilised teeth of Diictodon feliceps: plant-eating mammal-like reptiles less than half a metre long that were common at the time. The fossils come from the Karoo region of South Africa 鈥� which at the time, along with all the other continents, was part of the supercontinent Pangaea.

The teeth contained chemical evidence that the Karoo area became extremely arid around the time of the extinction. However, there was no evidence in the teeth of an increase in temperatures. Normally, warmer and drier climates go hand in hand, says Rey. 鈥淭he temperature seemed to stay constant through the interval,鈥� he says.

The team puzzled over this, until they realised that the fossils date from the time of the rise of South Africa鈥檚 Cape Fold Mountains. This mountain range may once have been as tall as the Himalayas are today.

Rey says the new mountains would have stopped moisture from the sea reaching Pangaea鈥檚 interior. This led to drying 鈥� and ultimately die-offs 鈥� without a corresponding increase in temperature.

The great dying

While that is plausible, the Cape Fold Mountains did not span all of Pangaea, so it seems unlikely that they caused the global Capitanian extinction on their own, says Lucas. 鈥淚t鈥檚 a big planet,鈥� he says.

鈥淲e are saying it鈥檚 a local signal,鈥� agrees team member of the University of the Witwatersrand. 鈥淏ut it might well be a global signal.鈥� He says the rise of the mountains could have been part of a mosaic of extinction drivers occurring around the same time.

Researchers are eager to solve the Capitanian extinction, because this once-obscure event could turn out to be to one of the worst disasters ever to strike life on Earth.

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