A team of researchers have identified the teeth, which were found in the Yukon in the 1970s, as belonging to hyenas one million years ago.
Their findings were published on Tuesday in scientific journal Open Quaternary.
The discovery sheds new light on the evolution of the ferocious scavengers.
The two teeth were found during a paleontological expedition in Yukon’s Old Crow Basin in 1973.
Indigenous explorers have been working with scientists to plumb the treasures of the region for over a century, says Grant Zazula, a palaeontologist with the Yukon government. But out of more than 50,000 specimen collected, only two that could belong to a hyena have been found.
It took nearly 50 years to find out what they were and who they belonged to. The teeth wound up on display at the Canadian Museum of Nature in Ottawa, which is where Mr Zazula first saw them.
Scientists had long hypothesised that they could belong to hyenas, but the theory had not been confirmed.
Mr Zazula teamed up with Jack Tseng, an evolutionary biologist with a specialty in hyenas at the University of Buffalo and Lars Werdelin at the Swedish Museum of Natural History.
“A meeting of minds came together,” Mr Zazula told the BBC. “Because (Tseng) is so well-versed in hyena fossils he knew instantly right away what they were.”
More testing determined the age of the fossils to be between 850,000 and 1.4 million years old.
How did the fossils get there?
Although modern-day hyenas mostly live in Africa, fossils belonging to ancient genus have been found as far north as Mongolia and as far west as Mexico.
That’s a 6,000 kilometre gap.
These fossils help connect the dots, and confirm the hypothesis that they arrived to North America from Russia on the Bering Strait, Mr Zazula said.
They also suggest that ancient hyenas had a very different life than ones today.
“We’re so used to thinking of Hyenas living in places like Africa, where they’re running around the savannah, he said. “But to think of them living in snow and 24-hour darkness in the winter is totally different.”