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The fossil bed found by Jean-Bernard Caron’s team in Kootenay National Park is the biggest and most diverse in decades.ROM

What intrigued Jean-Bernard Caron was the way the dark stone sparkled in the sunlight. What thrilled him was the reason: every sparkle was the glint of an ancient eyeball shining back at him across half a billion years of time.

The abundance of those eyes, along with the preserved remains of thousands of specimens that come with them, speaks to the spectacular richness of a newly documented fossil site in the Canadian Rockies.

"This is a new motherlode," said Dr. Caron, a paleontologist with the Royal Ontario Museum, and leader of the international team that made the discovery. A description of the find is scheduled for publication Tuesday in the journal Nature Communications.

According to Dr. Caron, the find promises to rival or even surpass the Burgess Shale, located less than 50 kilometres away. That formation, discovered more than a century ago, was the first to reveal a strange and vibrant stage in the emergence of animal life.

Like the Burgess Shale, the new find dates back to the Cambrian Period, some 505 million years ago and it has yielded some of the same bizarre creatures. But Dr. Caron's teams also found fossil types that had previously only been seen in Asia, along with others never encountered by scientists anywhere.

"This kind of diversity hasn't been seen in decades," said Douglas Erwin, a curator with the Smithsonian Institution in Washington, D.C. who was not involved in the discovery. "They're not simply getting things have already shown up."

The fossil bed was discovered in 2012, in a section of Kootenay National Park in British Columbia that cannot be accessed by trails. Although the team is not sharing the site's precise location – to protect it from pillaging by would-be fossil hunters – Dr. Caron said it was near a scenic feature called Marble Canyon.

"It's on the side of a mountain like any other mountain," said Alex Kolesch, a manager with Parks Canada. "To be able to discern what's there, you would really need to know what you're looking for."

The team first stumbled upon the site while looking for exposed sections of rock similar to that found in the Burgess Shale. One evening, they came to a place where it seemed that fossils were littering the ground. Upon closer inspection, they realized it was no fluke, but the eroding edge of a significant deposit that previous expeditions had missed. Within days, there were pulling out high-quality specimens of ancient marine life in stunning numbers.

The fossils are remarkable for the degree of preserved detail in some of the specimens, including features related to eyes, joints and nerves that should shed light on the early evolution of animal life.

Initial highlights from the site include distant relatives of today's insects and crustaceans, as well as a hitherto rare fossil type called Metaspriggina, a limbless, eyeless creature that nevertheless represents a distant precursor to all animals with a spine, including humans.

All the specimens found at the site lived on the ocean bottom and were later covered with a muddy silt, which gradually became a fine-grained rock. When carefully split open, the rock reveals the remains of the specimens locked within, including their soft tissues – crucial for studying animals that otherwise would leave few if any trace behind.

Animal fossils of the period are of interest because they capture a moment when life seemed to explode with variety, giving rise to the main divisions of existing animal species along with others long since passed into oblivion.

"There's a lot more to come," said Dr. Caron, who added that the new site, which seems to be far larger in extent than the Burgess Shale formation, promises to give a "more complete view" of a world that vanished long before dinosaurs were around.

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