The tusks were illegally taken between Calgary and Yukon/Alaska border in 1960

A pair of mammoth tusks that had been illegally acquired by an American collector in 1960 have been returned to Canada.

The tusks were recovered during an FBI investigation into Indiana collector, Don Miller in 2014.

Miller told the FBI he had excavated the tusks on a trip he took between Calgary and the Yukon-Alaska border. He took the tusks across the border and transported them to his home in Indiana, where they remained until 2014.

The tusks are now in the care of the Canadian Museum of Nature’s national fossil collection in Gatineau, Que.

The 1.5-metre-long tusks appear to be in good condition, according to Kieran Shepherd, one of the museum’s curators.

“These are fairly well-preserved specimens, and we are grateful for the cooperation of the United States government and the FBI in ensuring these pieces of Canada’s fossil heritage have been returned,” Shepherd said in a news release.

Miller told the FBI he originally thought the tusks belonged to a mastodon — a similar-looking mammal but slightly smaller than mammoths.

Tests conducted by the museum’s fossil experts revealed the tusks indeed belonged to a mammoth. The test involved cutting a small fragment from the tusk and looking at patterns on the inner layer — similar to looking at growth rings in trees.

The patterns were examined by mammal expert Dr. Danielle Fraser.

“We could see that the inner layers of the tusks showed the ‘w’ pattern characteristic of mammoths. If the tusks belonged to a mastodon, we would expect to see a checkered pattern.”