Fossil hunters Jean-Bernard Caron and Robert Gaines walk through the wreckage of a forest fire, cross a creek by balancing on logs, hike up loose mountain rocks and lateral moraines above the treeline – all to reach the bottom of an ocean.

Here, below the toe of Stanley Glacier in British Columbia's Kootenay National Park, they search for missing links – animal ancestors and fragments of our past. The professional rock-busters are after fossils, and have found about 10 creatures no one had ever seen before. They occasionally find fossils with prey trapped in the bellies of predators – last meals consumed 500 million years ago.

These rocks are similar to the Burgess Shale, one of the world's best-known fossil fields in Yoho National Park, just west of here. Finding new and well-preserved creatures increases the diversity of the animal kingdom, broadening what we know about our roots.

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"We're not collecting stamps here," says Prof. Gaines, chair of the geology department at Pomona College in California. "We're understanding the beginning of our family tree. It's grandma in here."

Finding ancestral graves, or at least the outer edges of the cemeteries, requires simple tools: a chisel, hammer, good eyes, perhaps a magnifying glass, and patience. Profs. Gaines and Caron – the latter is curator of invertebrate paleontology at the Royal Ontario Museum and a professor at the University of Toronto – pick out chunks of stone in the fossil-bearing rock band 32 metres high and hope history appears.

They chisel, chisel, chisel the length of the middle of a rock until they see a fracture. Then they do the same at the fracture until the grey rock splits in two. The researchers inspect the face of the split rock, and if nothing excites them, they toss it aside and repeat the process. The repetition can be dull until they find new shapes – forms of life last spotted half a billion years ago.

"Usually there is a swear word and everyone turns around," Prof. Caron says.

The fossils look like reflective blobs, rather than preserved bones associated with famous dinosaur finds. They are easy to miss if the light is not quite right or you don't know what you're looking for. The ancient mud captured the squishy stuff – think guts and eyes.

Their team's most important newfound fossil, Profs. Caron and Gaines say in unison, is the species named Stanleycaris hirpex. It was a predator with appendages like rakes, perhaps used to comb prey into its mouth.

This critter may have been the top of the food chain in this corner of the ancient ocean. While the find increases the diversity of predators in the Cambrian explosion – an era defined by a burst of life forms – it presents a problem. The fossil record here is rich in predators, short on prey. Finding missing links like the Stanleycaris highlights how many more links remain missing.

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"The mystery not yet resolved is we don't know the preys – we don't have many candidates," Prof. Caron says.

That may change shortly. Profs. Caron and Gaines are even more keen on another new fossil find. This new discovery, however, makes them cagey. They won't reveal its location, save for hinting it is near the Stanley Glacier site. The newest Burgess Shale-like discovery further increases diversity in this neighbourhood of the animal kingdom, they say, and the quality of the preservation makes them giddy.

Even at the Stanley Glacier site there is plenty more work to do. A German adventurer found the first fossil here in 1996 and reported it to authorities. Preliminary scientific legwork followed in 2007, and the first expedition, led by Prof. Caron, started chiseling away here in August, 2008.

Profs. Caron and Gaines believe that expedition only scratched the surface. They did not have permission to camp near the site, so they had to trek to the fossil find, about two hours each way. The daily hike meant they returned home with fewer fossils, and fewer inches around their waists – they dubbed it the Burgess Shale Workout.

Next time they are allowed back to the field – they need Parks Canada's permission to search for and remove fossils – the scientists would love to trade their chisels for jackhammers to get further inside the mountains. Prof. Gaines, who conducted his PhD research in western Utah, puts the potential in perspective.

"I found more animals in half a day here than I did in six years there," he says.