Fossil hunters have traced the rise of the dinosaurs back to the freezing winters the beasts endured while roaming the Far North.
Animal footprints and stone deposits in northwest China suggest dinosaurs adapted to cold in polar regions before a mass extinction paved the way for their reign in the late Triassic .
With a blanket of fuzzy feathers to keep them warm, the dinosaurs were better able to cope and take advantage of new territories when brutal conditions wiped out large swaths of more vulnerable creatures.
“The key to their eventual dominance was very simple,” said Paul Olsen, the study’s lead author at the Lamont-Doherty Earth Observatory at Columbia University. “They were basically cold-adapted animals. When it was cold everywhere, they were ready, and the other animals weren’t.
The first dinosaurs are believed to have appeared in the temperate south over 230 million years ago, when most of the landmass made up a supercontinent called Pangea. Dinosaurs were initially a minority group, living mostly at high altitudes. Other species, including ancestors of modern crocodiles, dominated the tropics and subtropics.
But at the end of the Triassic, around 202 million years ago, more than three quarters of land and sea species were wiped out in a mysterious mass extinction event linked to vast volcanic eruptions that plunged a much of the world in cold and dark. The devastation set the stage for the reign of the dinosaurs.
Writing in Science Advances, an international team of researchers explain how the mass extinction may have helped dinosaurs become dominant. They started by examining dinosaur footprints from the Junggar Basin in Xinjiang, China. These showed that the dinosaurs hid along the coasts at high latitudes. At the end of the Triassic, the basin was well inside the Arctic Circle, about 71 degrees north.
But the scientists also found small pebbles in the normally fine sediments of the basin, which once housed several shallow lakes. The pebbles have been identified as “glacial debris”, meaning they were washed from the shores of the lake over patches of ice before sinking to the bottom when the ice melted.
Taken together, the evidence suggests that dinosaurs not only lived in the polar region, but thrived despite the freezing conditions. Having adapted to the cold, the dinosaurs were on the verge of conquering new territories as the dominant cold-blooded species perished in mass extinction.
Stephen Brusatte, professor of paleontology at the University of Edinburgh, who was not involved in the research, said dinosaurs were often typecast as beasts living in tropical jungles. The new research showed they would have been exposed to snow and ice at high latitudes, he said.
“Dinosaurs would have lived in these freezing, icy areas and would have had to deal with snow and frostbite and all the things that humans living in similar environments have to deal with today. So how did the dinosaurs been able to do it? Their secret was their feathers,” he said.
“The feathers of these early primitive dinosaurs would have provided a fluffy coat to keep them warm in the cold high latitudes. And it seems these feathers later came in handy when the world suddenly and unexpectedly changed, and giant volcanoes began to erupt in the late Triassic, plunging much of the world into cold and darkness in repeated winter volcanic events.
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