The world's northernmost dinosaur discovery is shedding light on prehistoric life in the far north during the Cretaceous period, according to a new study published in the journal Arctic.
A hadrosaurid vertebra found on Axel Heiberg Island in Canada's Nunavut territory adds to evidence that dinosaurs lived year-round in the far north during the Cretaceous, despite scarcity of daylight and food sources. The Cretaceous, an estimated 145 to 66 million years ago, followed the Jurassic period.
Though the dinosaur's vertebra was discovered decades ago -- in 1992 -- it is a prized find that continues to be analyzed by scientists.
Axel Heiberg Island, off eastern Canada's Ellesmere Island, is one of the northernmost spots of land on the Earth today. But in the Cretaceous period, when the animal that owned the preserved vertebra was alive, the island was at a more southerly latitude than the dinosaur-rich North Slope of Alaska, the study points out. The North American continent was in a different position at that time, tilted in a clockwise direction that sent what is modern-day Alaska farther north and modern-day Nunavut farther south, the study says.
What is important about the existence of a dinosaur bone at this site, said the study's lead author, is that is shows that this animal and others like it were able to live in isolation in the Far North without any migration south in the winter. "They obviously had no issues about the areas that are far north," said Matthew Vavrek, head paleontologist and curator at the Philip J. Currie Dinosaur Museum in Wembley, Alberta.
Remote Axel Heiberg Island was even more isolated in the Cretaceous period than it is now, according to the study.
What is now Nunavut was cut off for most of that period by a seaway running from the Arctic Ocean to the Gulf of Mexico, dividing North America into sections, Vavrek said. Water covered much of what is today's continental land, separating Nunavut from the rest of North America, he said.
"At various times during the Cretaceous, North America was probably 40 percent smaller, if not more, than it is today," he said.
The Far North -- including Nunavut and Alaska's North Slope -- was much warmer during the Cretaceous period, but it was far from tropical, according to paleontologists. The climate was more like that of the northern Rockies or the Pacific Northwest, they say. That means dinosaurs living on Axel Heiberg Island in the Cretaceous period, like those on the North Slope, had to function in relatively cold temperatures, Vavrek said. "There's no reason why they shouldn't have the ability to regulate their body temperatures," he said. However, there is still debate on what those temperatures were, he said. "There's no real consensus at this point as to the internal body temperatures of dinosaurs," he said.
Plenty of dinosaurs likely roamed what is today's Nunavut during the Cretaceous era, Vavrek said. But discoveries have far lagged those on Alaska's North Slope, which has proved to be an important region for polar dinosaur studies, he said.
Experts in Alaska paleontology recently announced discovery of a pygmy tyrannosaur, which followed analysis that in 2011 revealed existence another previously unknown species, now named Pachyrhinosaurus perotorum.
Nunavut's geology is not as favorable to preservation as that on the North Slope, Vavrek said. Most of the finds to date have been in marine rock and have been of ancient marine reptiles or fish, not dinosaurs, he said. The lucky paleontologists who have made dinosaur discoveries there have found fragments or chunks of bone that, long ago, somehow slipped into marine sediments that later became rock, he said.
"It's not that the animals weren't there. More than likely, it's that the animals weren't preserved," he said.
In contrast, the North Slope, and particularly the banks of the Colville River, which flows into the Arctic Ocean, has proved rich with relics that are preserved in sediments that covered the land -- and whatever dead dinosaurs happened to be there. "The area seemed to be a good spot for a lot of life, but it also seemed somewhat boggy," Vavrek said. The nearby mountains sent sediments down their slopes, providing a convenient preservation layer over the dinosaur relics, he said.
Another reason that discoveries on the North Slope have far outpaced those in remote parts of Nunavut is access by paleontologists, he said. There is some road access to the North Slope, and reasonable air access to study sites. By contrast, visitors to remote parts of Nunavut face very high travel costs for expeditions to remote areas, he said. Consequently, there have been about 10 times more man-hours devoted to North Slope dinosaur sites compared to Nunavut sites, he said. "Really, if you're not putting in the time, you're not going to be finding the things," he said.
Though the vertebra on Axel Heiberg Island is the world's northernmost dinosaur find, there have been discoveries on a Nunavut Island to its south. Expeditions to Bylot Island have resulted in discovery of remains of tyrannosaurs, probably related to other eastern North American tyrannosaurs; ornithomimosaurs, which are likened to modern ostriches; duck-billed hadrosaurs and some small carnivores, Vavrek said.
Contact Yereth Rosen at email@example.com
CORRECTION: The site of the Philip J. Currie Dinosaur Museum was wrong in a previous version of this story. It's in Wembley, Alberta.