The bones are discoloured with age and broken into hundreds of pieces. But when laid side by side, the fragments reveal the outline of a mighty beast – a rhinoceros – that roamed Canada’s High Arctic roughly 23 million years ago.
Long before the caribou, polar bear and musk ox emerged as icons of Canada’s northern wilderness, the rhinos were there, munching their way across a surprisingly verdant landscape while aurora borealis danced overhead.
That’s the picture that emerges from the first comprehensive analysis of a rhinoceros skeleton unearthed in stages from the permafrost on Devon Island in Nunavut.
Epiatheracerium itjilik, as imagined in ancient Nunavut with other animals whose fossils have been found there. The seal-like mammal in the water, Puijila darwini, spent most of its time walking on land.Julius Csotonyi
Labels on the rhino’s remains note their origin on Devon Island, part of the Arctic archipelago.Dave Chan/The Globe and Mail
Details about the fossil, published Tuesday in the journal Nature Ecology and Evolution, show it to be a member of the rhino genus Epiaceratherium. However, it is a distinct species within that group, which researchers who conducted the analysis at the Canadian Museum of Nature in Ottawa have dubbed itjilik‚ an Inuktitut word that translates as “frosty.”
What could prove controversial about the find is the team’s conclusion that the rhino’s nearest known relatives lived in Europe – a result that implies its ancestors crossed into the Canadian Arctic using a North Atlantic land bridge during the early Miocene period.
While such a bridge is known to have existed at much earlier times, the conventional view is that the connection was severed tens of millions of years before the rhinos could have arrived by that route.
Modern rhinos come from Africa – like the eastern black rhino ancestors of this baby at a Cleveland zoo – or from Asia. Their ancient European cousins are long extinct.Sue Ogrocki/The Associated Press
“Immediately I thought, this doesn’t make any sense,” said Danielle Fraser, the museum’s head of paleobiology and the lead author of the study.
Yet, she said, after a detailed modelling of itjilik’s family tree and a review of current research, she found support for the possibility that a dry land connection between Europe and Canada “persisted longer than we thought.”
The result, she added, reflects the emerging importance of the region as a cradle of mammalian evolution at a time when the Arctic climate was significantly warmer than it is today.
“If you’re a biodiversity scientist, you think about the tropics as the area that’s so important for evolution,” Dr. Fraser said. “But when we look to mammals in the past, the Arctic just seems to be the centre for diversification and dispersal.”
Devon Island is so desolate that NASA scientists have done field expeditions there, like this one in 2000, to get a sense of what life on Mars might be like. Haughton Crater adds to the unearthly aura of the place.
Bob Weber/The Canadian Press
The story of itjilik begins many thousands to millions of years before the fossil itself, when a small asteroid slammed into Devon Island’s ancient shale bed, excavating a deep crater more than 20 kilometres across.
Today that depression, known as the Haughton impact crater, resembles a giant quarry in the midst of barren plains that cover the world’s largest uninhabited island. But when the strike happened, Devon Island was home to a temperate forest that would have looked more like the environs around Ottawa today. The crater became a lake with abundant wildlife hugging its shoreline.
It was in this setting that the rhino lived and died, leaving its bones buried in muddy silt that remained hidden as the land grew colder and drier. Eventually the planet descended into an ice age, and glaciers permanently covered the area for vast stretches of time.
The saxifrage on today Devon Island is a far cry from the greenery that existed here millions of years ago.Bob Weber/The Canadian Press
In 1984, Mary Dawson, a pioneering Arctic paleobiologist at the Carnegie Museum of Natural History in Pittsburgh, was exploring a small valley in the Haughton crater when she spotted what turned out to be a piece of rhinoceros tooth embedded in the sediment. Two years later she returned and collected a large number of bones, including parts of the skull and jaws from the same location.
Between 2007 and 2010, successive Canadian Museum of Nature expeditions led by Natalia Rybczynski collected more bones at the site while working alongside Dr. Dawson, who was then in her 80s. “It was like she was playing in her own backyard,” said Marisa Gilbert, who participated in the expedition and would later spend years assembling the rhino bone fragments back in Ottawa.
The repeat visits were crucial, Dr. Rybczynski said, because of the process known as cryoturbation, a gradual overturning of the soil due to the freeze-thaw cycle. “We can go back to the same spot and new bones will have grown up out of the sediment,” she said.
Mary Dawson and Dr. Rybczynski, prospecting for fossils at the Haughton Crater in 2010, would make many trips to Devon Island as the thawing earth gave up more bones.
Courtesy of Canadian Museum of Nature
Having a mostly complete skeleton means Marisa Gilbert and her colleagues have more details to compare against other species of ancient mammals.Dave Chan/The Globe and Mail
In total, about three-quarters of the rhino’s bones have been recovered, making it an unusually complete skeleton. This helped to locate it within the rhino evolutionary tree. The bones show the rhino was a mature adult that stood about 1.5 metres at the shoulder. Based on the tusks of the lower jaw, the specimen could have been a female, but that is not certain without a male fossil for comparison, Dr. Fraser said. Like most ancestral members of the rhinoceros family, there is no evidence the creature sported a nasal horn like those associated with African rhinos today.
A further trove of biological information was published earlier this year, when it was revealed that enamel proteins were successfully extracted from one of the rhino’s teeth.
But the key question is how the rhino came to be there, on the banks of a Canadian crater lake 23 million years ago, and whether its evolutionary story involves a bridge to Europe. Such an idea is “pure fantasy and conflicts with all geological evidence,” said Philip Sexton, a paleoceanographer and senior lecturer at Britain’s Open University in Milton Keynes who was cited in the Ottawa team’s study.
But other clues, including a study of ancient oak tree pollen in Iceland, suggest the idea may not be so far-fetched. What would counter the idea would be the discovery of related rhinoceros fossils in northern Asia, which could indicate an alternative pathway to North America via the Bering land bridge, which is known to have existed at that time.
Even more tantalizing is the possibility that something more definitive may await discovery in the Haughton crater and other High Arctic sites in Canada that have yet to be explored. “The interesting thing is that the only large mammal that we have from the crater is the rhino,” Dr. Fraser said, noting that the Miocene was populated by an abundance of large mammals, including camels and horses. “Where are they? I feel like they were there and I feel like we’re going to find them,” she said.
Dave Chan/The Globe and Mail
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