A giant, flightless bird with a horse-sized head roamed the winter landscape of the high Arctic approximately 53 million years ago, researchers from the University of Colorado at Boulder confirm in a new study. This is the first fossil evidence -- comprised of only a single toe bone -- of the massive "Gastornis" to be found in the Arctic.

Weighing several hundred pounds, Gastornis -- formally Diatryma -- stood about six feet tall. 

"We knew there were a few bird fossils from up there, but we also knew they were extremely rare," Jaelyn Eberle, co-author and associate professor of geological sciences at CU-Boulder, said in a news release.

Although the Gastornis fossil was originally collected from Ellesmere Island above the Arctic Circle in the 1970s, the recent study marks the first time it has been examined closely. The fossil toe bone is nearly identical to those discovered in Wyoming that date to the same time period. Similar fossils have also been discovered in Europe and Asia.  

The toe fossils were dated to be about 53 million years old, from a time period known as the Eocene Epoch. While Ellesmere Island is considered one of the coldest and driest places on Earth today, 53 million years ago the environment was much more similar to the cypress swamps seen in the southeast U.S. Other fossil evidence found on the island suggests turtles, alligators, primates, tapirs and even large hippo-like and rhino-like mammals lived among Gastornis.

Previously, the massive bird was thought to be a fearsome carnivore; however, the study indicates Gastornis was likely a vegan and used its huge beak to tear apart foliage, nuts, seeds and hard fruit.

In their hunt for Gastornis, researchers also discovered a single fossil humerus, or upper wing bone, belonging to a second Ellesmere Island bird from the early Eocene. Presbyornis, as it has been named, closely resembles modern ducks, geese and swan, but with longer, flamingo-like legs. 

When comparing casts of Presbyornis bones excavated in ancient Wyoming to the single bone from Ellesmere Island, co-author Thomas Stidham of the Chinese Academy of Sciences said: "I couldn't tell the Wyoming specimens from the Ellesmere specimen, even though it was found roughly 4,000 kilometers (2,500 miles) to the north."

In addition to revealing the early biodiversity of Ellesmere Island, the study warns of the dangers surrounding a rapidly warming Arctic, which is largely a result of greenhouse gases being pumped into Earth's atmosphere by human activity. 

"Permanent Arctic ice, which has been around for millennia, is on track to disappear," Eberle added in the university's release. "I'm not suggesting there will be a return of alligators and giant tortoises to Ellesmere Island any time soon. But what we know about past warm intervals in the Arctic can give us a much better idea about what to expect in terms of changing plant and animal populations there in the future."

Their study was recently published in the journal Scientific Reports

Related Articles 

Two New 'Big-Mouthed' Fish: Discovery Triples Known Species

Ancient Wildebeest Ancestor Had Nose Of Duck-Billed Dinosaur

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

-Follow Samantha on Twitter @Sam_Ashley13