The Burgess Shale: Evolution’s Big Bang

A storied trove of fossils from a Canadian paleontological site is yielding new clues to an explosion of life on earth

The rich fossil repository known as the Burgess Shale was first discovered a century ago. (Siobhan Roberts)
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The helicopter put down near Stanley Glacier, where Caron and Gaines joined the rest of the crew, who were already prospecting for fossils. It did not take long to hit pay dirt. On the first afternoon, Loxton found a fossil of a species fondly known as Creeposaurus (until it can be properly studied, identified and given its scientific name). Caron called out: "Champagne!" Only three other specimens of this tentacled, bottom-dwelling animal had ever been collected.

"Creeposaurus is a new species, but it's important for another reason as well," Caron explained. "It's helpful in understanding two animal lineages—one is like a starfish, an echinoderm, and the other is a plankton-like organism, a hemichordate. Creeposaurus may be a common ancestor and has the potential to unite these two animals that we know today."

The Stanley Glacier valley, which is shaped like an amphitheater, turned out to be the scene of a paleontological pageant. As the glacier melted, over the past few thousand years, it exposed a fresh outcrop of loose rock stretching for a mile and a half. "Extraordinary, amazing, to find so many animals here, lying around untouched from hundreds of millions of years ago," said Caron.

Over the next two weeks, he and his crew, occasionally using a diamond-bladed rock saw, would collect several hundred specimens, including what they believe to be four new species. One of them, an arthropod, was found in such profusion—appendages here, carapaces there—by so many crew members that it became a sort of site mascot the group dubbed "Stan Animal." "A very scary animal," Caron said of a specimen with spiky legs and multiple rows of teeth. "You don't want to have it in your sleeping bag at night."

After the end of the field season, Caron returned to the Royal Ontario Museum, where he swapped his worn and grubby hiking duds for laboratory whites. In the collections room, he flipped through a notebook, trying to make sense of the cans and crates full of rock that sat in a jumble at his feet. "It's a treasure chest waiting to be opened," he exulted.

Siobhan Roberts lives in Toronto. She is the author of King of Infinite Space.


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