Giant camels roamed the Arctic 3.5 million years ago, Canadian and British researchers have discovered.
The discovery, by a research team led by the Canadian Museum of Natural History, is based on 30 fossil fragments of a leg bone found on Ellesmere Island, Nunavut, the northern-most Canadian territory.
The discovered fossils of the camels, believed to be 30 percent larger than the modern "ships of the desert", are the most northerly record for early camels, whose ancestors are known to have originated in North America some 45 million years ago.
The fossils were collected over three summers in 2006, 2008 and 2010, and are about 3.5 million years old, dating from the mid-Pliocene Epoch. Other fossil finds at the site suggest this High Arctic camel lived in a boreal-type forest environment, during a global warming phase on the planet.
The date is significant as the Earth was 2°C to 3°C warmer than today, and the Arctic was 14°C to 22°C warmer.
The research, by Dr Natalia Rybczynski, a vertebrate palaeontologist with the Canadian Museum of Nature, and co-authors including Dr John Gosse, from Dalhousie University, Nova Scotia, and Dr Mike Buckley from the University of Manchester, England, has been published in the online journalNature Communications.
"This is an important discovery because it provides the first evidence of camels living in the High Arctic region," Dr Rybczynski said.
"It extends the previous range of camels in North America northward by about 1200 km, and suggests that the lineage that gave rise to modern camels may have been originally adapted to living in an Arctic forest environment."
The camel bones were collected from a steep slope at the Fyles Leaf Bed site, a sandy deposit near Strathcona Fiord on Ellesmere Island. Fossils of leaves, wood and other plant material have been found at this site, but the camel is the first mammal recovered.
Determining that the bones were from a camel proved to be a challenge, Rybczynski said.
"The first time I picked up a piece, I thought that it might be wood. It was only back at the field camp that I was able to ascertain it was not only bone, but also from a fossil mammal larger than anything we had seen so far from the deposits."
Physical characteristics suggested the fossil fragments were part of a large tibia, the main lower-leg bone in mammals, and that they belonged to the group of cloven-hoofed animals known as artiodactyls, which includes cows, pigs and camels.
Minute amounts of collagen, the dominant protein found in bone, were extracted from the fossils. The collagen profile most closely matched those of modern camels, specifically dromedaries (camels with one hump) as well as the Yukon giant camel, which is thought to be Paracamelus, the ancestor of modern camels. The collagen information, combined with the anatomical data, led Rybczynski and her colleagues to conclude the Ellesmere bones belong to a camel, and is likely the same lineage as Paracamelus.
"We now have a new fossil record to better understand camel evolution, since our research shows that the Paracamelus lineage inhabited northern North America for millions of years, and the simplest explanation for this pattern would be that Paracamelus originated there," Rybczynski said.
"So perhaps some specialisations seen in modern camels, such as their wide flat feet, large eyes and humps for fat may be adaptations derived from living in a polar environment."