Piecing together Yukon’s dinosaurs, one fossil at a time

Truckloads of mammoth and bison bones arrive at the Yukon palaeontology unit every year, dug up by placer miners, adding to an impressive collection of Ice Age specimens.

Truckloads of mammoth and bison bones arrive at the Yukon palaeontology unit every year, dug up by placer miners, adding to an impressive collection of Ice Age specimens.

But the further back in time you go, the less evidence there is. When it comes to the age of dinosaurs, you can hold the entire collection in the palm of your hand.

That’s not to say that dinosaurs weren’t here. They just haven’t been found yet.

In the summer of 2010, Carleton University paleontology student James Campbell was examining the shale along the banks of the Road River, a tributary of the Peel east of Eagle Plains.

As an intern with the Geological Survey of Canada, Campbell was collecting microfossils to determine the age of the rock exposed on a cliff side when his trained eye was drawn to a larger fossil sitting among the shale.

Campbell’s specimen doesn’t look like much, to be honest: it’s rough and chipped and multicoloured. But he knew immediately it was a vertebra, a section of spine, most likely from a fish or a marine reptile.

How did he narrow it down on the spot?

Previous mapping had dated the rock in the area to the later part of the early Cretaceous period. At that time, much of northeast Yukon was underwater.

The Western Interior Sea covered Eagle Plains, the Peel watershed, Alaska’s North Slope, the Mackenzie Delta and most of the Great Plains of North America.

Knowing this, any specimen found from that era would likely be from an aquatic species.

Upon initial inspection, fish was ruled out.

“I was quite sure it was a marine reptile,” said Campbell. “Fish vertebrae are concave, this one had relatively flat surfaces.”

Further examination narrowed it down to some kind of Elasmosaur, a family of long-necked, paddle-finned reptile.

“It looks like what you’d imagine the Loch Ness monster to be,” said Campbell.

After the find, Campbell returned to Ottawa to finish his degree and didn’t have time to write up his findings until 2013.

At that point, Yukon paleontologist Grant Zazula brought a second fossil into the picture.

The vertebrae of an Ichthyosaur, a dolphin-shaped marine reptile, was discovered by a fur trapper named David McDonald near the Beaver River in southeast Yukon in 1998, and sat in Yukon’s collection for 15 years.

The Ichthyosaur fossil is polished by weather and time, and has a distinctive depression in the centre.

Finding the source of the Beaver River fossil proved to be more challenging, because the rock in that area comes from the Triassic period, at least 100 million years earlier.

With the help of University of Alaska Fairbanks paleontologist Pat Druckenmiller, an expert in marine reptiles, they figured out that the fossil didn’t match its surroundings, chronologically speaking. A Triassic Ichthyosaur would be tiny.

“There’s no way it could be from that period, it’s way too big,” said Zazula.

They found that the specimen is also of the late-early Cretaceous, the same as Campbell’s fossil.

An outcrop of Cretaceous rock was located about four kilometres upstream on the Beaver, and that is considered the origin point. It’s thought that either the river or glacial action moved the fossil to the spot it was found.

Putting all these pieces together can help scientists draw some conclusions about life at that time.

During the late-early Cretaceous period, in the Albian age (113 to 100 million years ago) the Western Interior Sea extended south to what is now Texas but did not connect to the Gulf of Mexico. This means these large marine reptiles entered into the sea from the north, the Arctic Ocean, and would have lived and evolved in Arctic waters during that era.

Zazula hopes these discoveries will tweak people’s thinking about evolution in the High Arctic. “You can have incredible biodiversity at high latitudes,” he said.

Campbell, Zazula and several other scientists submitted their findings to the journal The Canadian Field Naturalist, which will hopefully spark some interest in other fossil-finding expeditions in the territory.

As it is, the Yukon is largely unexplored. Campbell’s find may change that. “This is how areas get opened up for research, a scratch at the surface,” said Zazula. “Once you get people with rock hammers on the ground, that know what they’re looking for, I think more stuff like this will be found.”

Contact Ian Stewart at

istewart@yukon-news.com

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