for National Geographic News
Most of us think of dinosaurs as roaming grassy plains and savannas in semi-tropical temperatures. But dinosaurs ranged all over the planet, and a small group of scientists is working to build the fossil record and introduce the world to the dinosaurs that lived at the top and bottom of the world.
The first indication that there even was such a thing as polar dinosaurs came in 1960 when footprints were found at Spitsbergen, an island that lies about half way between the coast of Norway and the North Pole. Since the initial discovery, the study of polar dinosaurs has slowly gained momentum.
"The biggest misconception we face is that people don't know they even exist," said Thomas Rich, a paleontologist at Museum Victoria, Australia. "Yes, the dinosaurs lived in steaming swamps and howling deserts, and on the plains, but they also got to high latitudes, and did very well, thank you very much."
Questions about polar dinosaurs abound: Did the animals migrate to warmer climes during the worst of the winter, did they hibernate, or did they remain active close to the poles even during the coldest part of the year? How cold was it? It's not that easy to establish a region's mean annual temperature 150 million years ago.
Writing in a recent issue of the journal Science, Rich and colleagues sum up the evidence known so far and conclude that the dinosaurs living in the polar regions were quite well adapted to their environment.
One of the puzzles polar dinosaur specialists face is establishing how cold it was, at what time period, where. The supercontinent Gondwana began to break up around 200 million years ago, creating new, smaller land massesAntarctica, South America, Africa, India, and Australasia. During the Cretaceous, 145 to 65 million years ago, the world climate was warmer than it is today, and the continents were still shifting; southeastern Australia lay within the Antarctic Circle.
Rich and his wife Patricia, a vertebrate paleontologist at Monash University in Victoria, Australia, and co-author of the report, have uncovered dinosaur fossils from about 105 to 115 million years ago, buried in sediment layers marked by ice wedges, permafrost, and hummocky ground. By looking at fossil pollen samples from sediment layers laid down over thousands to millions of years, they have been able to get an environmental snapshot of southeastern Australia during that time period.
"The mean annual temperatures (MAT) ranged between -6 to +3 degrees Celsius (21 to 37 degrees Fahrenheit)," said Rich. "For comparison, the MAT for Fairbanks [in Alaska] today is -2.9 degrees Celsius."
Roland Gangloff, a paleontologist at the University of Alaska Museum and co-author of the report, points out that mean annual temperatures are an average for the whole year. "If the temperature drops below -3 degrees Celsius in the winter, you're in frigid temperatures, and looking at everything that goes along with that," he said.
What goes along with frigid temperatures are ice and frozen ground, long periods of darkness, and a reduced food supply.
Almost half of the dinosaur fossils found in southeastern Australia are hypsilophodontids, small, speedy dinosaurs that ran around on two feet. The smallest probably stood somewhere between 18 inches to two feet (40 to 60 centimeters) tall, said Rich. Hypsilophodontids flourished for 100 million years and have been found all over the world, but were still somewhat rareexcept in Australia.
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