A massive beaver jaw preserved underground for about 50,000 years is believed to be from an ancient relative roughly the size of a bear or large football player that weighed as much as 300 pounds.

The rare fossil was discovered in late September by a worker at a southeastern Manitoba gravel pit who brought it into the Manitoba Museum. Graham Young, the curator of geology and paleontology at the museum, said the men who found it figured it was from a pig, because of what appeared to be a tusk.

“They were actually quite flummoxed when we said, “No, that is actually an extinct giant beaver,” he told CTV Winnipeg on Thursday.

The tusk is most likely a Castoroides ohioensis tooth.

Young said the ancient animal isn’t exactly a giant version of the woodland creature on the nickel, but there are some striking similarities. No big flat tail, and probably no dam building, but it may have lived in a lodge, and likely spent a lot of time in the water.

“This was a big relative that diverged from beavers quite a long time ago, and sadly like so many other ice age things, became extinct,” he said.

Young said the find is particularly noteworthy because it is the first of its kind in the province, and one of only four found in Canada.

“In terms of occurrences in Canada, this is a very rare fossil,” he said.

The fact that it remained relatively intact over tens of thousands of years is also a major stroke of luck, he explained.

Identifying its exact age isn’t easy, but pieces of spruce found in the clay layers of local gravel pits have been dated to about 44,000 years. Young said this piece is almost certainly from the last 100,000 years.

“This is something that dates before the last part of the ice age, before the last push of glaciers over southern Manitoba,” he said. “It’s miraculous when you think about all the things it could have been through.”

Young said the species was likely wiped out slowly, along with North American horses and lions, mastodons, short-faced bears, giant ground sloths and other ancient relatives to modern animals. The changing landscape, climate change, and declining food were most likely to blame. The spread of humans across the continent also shrunk the populations of some large mammals.

“If you killed a beaver the size of a bear, you could feed your family for quite a while,” Young said.

The fact that a jaw piece was found made the identification process easier for scientists at the museum.

“It’s cool to find a jaw, because you know right away what you have. You can imagine with a human skeleton, if you find a rib or if you find a vertebrae or a piece of a leg bone. How do you know what kind of a creature it is?” Young said. “You find a human jaw and you know right away that’s a person.”

The museum would like to put the giant beaver jaw on display for the public, but Young feels it’s too risky. He said it has to be kept moist, and dried very slowly to avoid deterioration. Right now, they are storing it in a special humidified room to keep it stable.

“They are very sensitive things,” Young said. “This is the only one in Manitoba, so we really have to care for it with extreme caution.”

With a report from CTV Winnipeg’s Gabrielle Marchand