But Rich says that the lives of polar dinosaurs can help researchers understand why dinosaurs went extinct after the impact. The catastrophe had to have been long and severe enough to kill off the dark- and cold-adapted animals. "You can't just have it [darkness] for a month and do the job," he says.
But Fastovsky says that polar dinosaurs tell us nothing about the animals' demise because we don't know whether these particular species were even alive at the end of the Cretaceous period. Rich's Australian dinosaurs were long extinct by the time the asteroid hit. Whether the dinosaurs on the North Slope of Alaska were alive is uncertain, he says; researchers have found no fossil layers there from the very end of the Cretaceous period.
For polar dinosaurs to provide more definitive evidence on dinosaur metabolism and extinction, we'll need more fossils. This year Rich embarked on a dig on Alaska's North Slope, his first. It's expensive work, and it took him 18 years to line up the funding necessary to transport, on a single-engine Otter plane and snow machines, his field party and their equipment, which included rock drills, chainsaws, jackhammers and explosives.
Rich and his advance team prepared the site on the Colville River, about 375 miles north of Fairbanks, in late March and early April, when the temperatures sink to minus 40 degrees Fahrenheit. They hired a miner to drive a horizontal shaft into the riverbank just above a layer of dinosaur fossils. Working at that time of year sounds crazy, Rich admits, but it's actually easier to dig a tunnel when the ground is frozen solid.
In August, the full ten-member team walked into the tunnel and extracted fossils from the floor. They are still sorting the bones, but Rich has already identified one notable find: a type of pachycephalosaur, a plant-eating dinosaur with an unusually thick skull that has been found only once before, also in Alaska. It might be the first known dinosaur that lived exclusively in the Far North, more evidence that the ancient beasts endured even the coldest and darkest days.
Mitch Leslie was a dinosaur fanatic as a child and studied reptiles before becoming a writer. He lives in Portland, Oregon.
Dinosaurs of Darkness, by Thomas H. Rich and Patricia Vickers-Rich, Indiana University Press, 2000
Dinosaurs of Australia and New Zealand and other animals of the Mesozoic Era, by John A. Long, Harvard University Press, 1998
The Evolution and Extinction of the Dinosaurs, 2nd edition, by David E. Fastovsky and David B. Weishampel, Cambridge University Press, 2005