That's a big beaver bone: Ice age giant-beaver jaw 1st of its kind found in Manitoba

Museum curators are accustomed to taking excited phone calls from people who think they've come across an ancient fossil, only to find on closer inspection the bone belonged to a common barn animal.

That's why Graham Young was so surprised when he first laid eyes on the "massive" tooth and jawbone of a giant beaver that would've weighed more than the average black bear.

"It's beautiful," said Young, the paleontology curator at the Manitoba Museum in Winnipeg. "The teeth are all there — not just that one big tooth, but the grinding teeth are also there. [They] seem to show a lot of wear and tear on them, so I think it was an old beaver when it died."

Exactly how old remains to be seen, but bits of petrified wood from the same area where the Castoroides fossil was recently found have been shown to be 44,000 years old, Young said.

The fossil is on a wait list to be radio carbon dated, which should yield a more precise age estimate.

The discoverer, who has chosen to remain anonymous, unearthed the bone in a gravel pit in southeastern Manitoba.

The person brought the bone into the museum over one lunch hour, freely admitting it might just be from a pig because it had a big "tusk-like tooth on it," Young said.

He met the person, who then unwrapped a series of bones that included a partially intact giant-beaver jaw. It had a vaguely familiar tooth still stuck at the end — only this one was ridged and thick, sharp, and much larger than the tooth of an average modern beaver.

"They recognized it was an odd creature. They had never heard of giant beavers," Young said. "Sometimes you just get very odd things brought into the museum."

He said one of the reasons why the discoverer didn't immediately see it for what it is relates to a problem of scale. Though it shares many of the same characteristics of a present-day beaver, the size discrepancy might make it hard for the average Canadian to make the connection.

"I was very excited," Young said, adding he and others at the museum quickly reached a consensus that this was from a giant beaver.

A review of paleontological records revealed this to be just the fourth such giant-beaver bone discovered in Canadian history — and a first for Manitoba.

"I knew that we had none in our collection from Manitoba, genuine ones, because when we wanted to do an exhibit we had to buy copies," Young said.

"So clearly it was a new thing to our collection and therefore I thought it was probably a new thing to Manitoba, because ... most of the ice age things that have been collected in Manitoba are in the collection of this museum."

Paleontologists generally believe giant beaver species ranged between 90 to 135 kilograms (200 to 300 pounds), Young said. Estimates put the average length of the extinct rodent at nearly two metres (greater than six feet long).

To put that into perspective: the average weight and height of Canadian men has been pegged at five feet 10 inches and 191 pounds, according to Statistics Canada. And the modern North American beaver — the largest rodent on the continent — tips the scale at between 10 and 32 kilograms (or 20 to 70 pounds).

Scientists believe the last group of giant beaver species went extinct near the end of the last ice age, about 10,000 years ago.

A close relative of the beavers that are now a fixture of the Canadian landscape existed at the same time as their comparatively massive cousins.

"This is such a rare and utterly unique fossil," Young said.

As for the Manitoba specimen, Young says it became saturated during the thousands of years it rested beneath the water table. 

The fossil is being slowly aired out in a climate-controlled environment right now to ensure it's around and on public display for generations to come.