More than 50 million years ago, a giant flightless bird that weighed several hundred pounds lived in the Arctic.

Based on a single toe bone first found in the 1970s, researchers from the Chinese Academy of Sciences in Beijing and the University of Colorado Boulder determined that the bird, named Gastornis, lived in the Arctic Circle on Ellesmere Island.  

"People thought there was a larger bird up there but the fossils had never been described," CU-Boulder’s Jaelyn Eberle, a co-author of a study on the bird that appeared in Scientific Reports, told FoxNews.com of the bone which was in the collection of the Canadian Museum of Nature.

"There are lots of wonderful discoveries we can make in the field," she said. "But I would say there are a lot of great discoveries that can be made in collections that have been hanging around for a while but, for whatever reason, hadn't been described. We knew there were birds but nothing had been described until this paper."

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Eberle and the lead author on the study, Thomas Stidham, then compared the bone to those of similar bird fossils found in other parts of the world. They concluded it may be of the same genus as giant birds found in mid-latitude locations.

"Gastornis has been known from mid-latitudes for a long time, from Wyoming, Colorado, Europe. What we were able to do was compare that fossil from the Arctic to all of these mid-latitude specimens," she said. "I think what is interesting is that the toe is virtually identifical to specimens from Wyoming. The difference is they are 4,000 kilometers (2,485 miles) apart. That is kind of strange."

Coming upon this bird would have been a terrifying sight and researchers initially believed it was a fearsome carnivore. It would have stood 6-feet-tall and been about the size of an adult male with a head about the size of a horse's head.

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But more recently, other researchers had found that it been a vegan, using its huge beak to tear at foliage, nuts, seeds and hard fruit. And unlike the harsh conditions of Ellesmere Island today where temperatures can drop to minus 40 degrees in winter, the bird’s environment about 53 million years ago would have been similar to cypress swamps in the southeast, Eberle said.

"It was still formidable but it was the plants that had to be fearful," Eberle said.

Fossil evidence indicates the island, which is adjacent to Greenland, hosted turtles, alligators, primates, tapirs and even large hippo-like and rhino-like mammals.

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And unlike modern day ducks and geese that migrate through the Arctic, Eberle said Gastornis was most likely a year-around resident. It would have had enough to plant material eat, she said, and probably wouldn't have had the energy to migrate elsewhere.

"We would hyphosize that a large bird, just like large mammals up there, could overwinter in the Arctic," she said. "Because this is a land dwelling bird, I think they were permanent residents. Part of it is because - this is the same argument we use for the mammmals up there -  it's energetically expensive for an animal that walks on land to travel from Ellesmere Island down the tree line each year."