Robert Gaines, a Pomona College professor of geology, was part of the team that has discovered a stunning new Burgess Shale fossil site in Canada's Kootenay National Park. The massive deposit may be the world's most important fossil discovery in decades. In a paper published today in Nature Communications, the team describes the new ‘Marble Canyon' fossil beds for the first time.

The original Burgess Shale locality, discovered by Charles Walcott in 1909, is one of the world's most important fossil sites and home to some of the planet's earliest animals, including a very primitive human relative. That site was designated one of Canada's first UNESCO World Heritage Sites in 1980. The Marble Canyon fossil beds appear to equal the importance of the original discovery, and may one day even surpass it.

Burgess Shale deposits date from the Cambrian Explosion and contain exquisite preservation of the whole fossil community – not just shells and bones, but soft parts. "Because most animals in the ocean don't have ‘hard' parts," says Gaines, "these fossils gives scientists unparalleled insight into the magnitude and patterns of the explosive origin of animals, because everybody – worms, jellyfish, soft arthropods, etc. – is preserved."

The find was made in the summer of 2012 by Jean-Bernard Caron (Royal Ontario Museum-ROM), Robert Gaines (Pomona College), Cédric Aria (University of Toronto), Gabriela Mángano (University of Saskatchewan), and Michael Streng (Uppsala University).

"We were already aware of the presence of some Burgess Shale fossils in Kootenay National Park," says Gaines. "We had a hunch that if we followed the formation along the mountain topography into new areas with the right rock types, maybe, just maybe, we would get lucky – though we never in our wildest dreams thought we'd track down a mother lode like this. It didn't take us very long at all to realize that we had dug up something special."

Once the team discovered the fossils, lying in loose talus that had collapsed off of the steep cliff above, it was up to Gaines to find the precise levels within the formation that had yielded the fossils. When they began to break into the fresh rock at the level that Gaines identified, the team was not disappointed. "I've never had the experience of putting my hammer into rock and splitting out magnificent specimens, time and time again," says Gaines.

In 15 days of fieldwork, the team recovered more than 3,000 fossils, with most preserved in stunning anatomical detail, even by Burgess Shale standards, says Gaines. In more than 100 years of research at the original Burgess Shale site, approximately 200 animal species have been identified.

"We have a total diversity of 55 species so far, and the number will grow with further collection," reports Gaines. Among the highlights, a startlingly large proportion of species (22%) are brand new to science. This is surprising because the Burgess Shale is so well-collected, with almost 200,000 known specimens. This means that our new site represents a slightly different environment that was inhabited by different critters."

Other highlights include a particularly abundant and diverse collection of arthropods including new species and several species previously known only from deposits in China that are approximately 10 million years older.

These species, says Gaines, were assumed to be extinct by the time of the Burgess Shale, and/or restricted to China. "This new find is important because it shows that the longevity of many Cambrian species may be severely underestimated. The same goes for their geographic ranges. We are reminded that absence of evidence of their presence in the fossil record is not true evidence of absence. We may need to re-think how we interpret patterns of animal evolution and extinction using unusually-well preserved fossil assemblages."

"Lots of us who are interested in exceptional fossil deposits have spent months, even years, working at sites discovered long ago, by scientists who have come before us," says Gaines. "We often wonder what it must have felt like for Walcott to walk across the slopes below his original Burgess Shale site and to find the first fossils laying under the sun, untouched or picked over by human hands. But these moments of discovery seem to belong to a bygone era. You never truly imagine that there's another mother lode lying out there undiscovered on a mountain's slope, never before seen by paleontologists. I will never forget that experience."

The original Burgess Shale site, located in Yoho National Park, attracts thousands of visitors each year for guided hikes to the restricted fossil beds from July to September. The new fossil site is protected by Parks Canada, with the exact location remaining confidential to protect its integrity, though future visitor opportunities have not been ruled out.

All the Burgess Shale fossil specimens in the Marble Canyon area of Kootenay National Park were collected under a Parks Canada Research and Collection Permit. The ROM holds the world's largest collection of Burgess Shale fossils, which are held in trust for Parks Canada.

According to the article's lead author, Dr. Jean-Bernard Caron, curator of invertebrate paleontology at ROM and associate professor at the University of Toronto, "This new discovery is an epic sequel to a research story that began at the turn of the previous century, and there is no doubt in my mind that this new material will significantly increase our understanding of early animal evolution."

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