Fossil hunters trace the rise of dinosaurs to the freezing winters the beasts endured as they roamed the far north.
Animal footprints and fossils from northwestern China suggest that dinosaurs adapted to the cold of the polar regions before a mass extinction event paved the way for their dominance at the end of the Triassic period.
Fuzzy feathers helped them stay warm, allowing dinosaurs to cope and exploit new territories when brutal conditions wiped out large swaths of vulnerable species.
“The key to their eventual dominance is very simple,” said Paul Olsen, lead author of the study at Columbia University’s Lamont-Doherty Earth Observatory. “They’re essentially cold-adapted animals. When it got cold everywhere, they were ready, and other animals weren’t.
The first dinosaurs are thought to have appeared in the temperate south about 230 million years ago, when most of Earth’s land mass formed a supercontinent called Pangea. Dinosaurs were initially a minority group, living mainly at high altitudes. Other species, including the ancestors of modern crocodiles, dominated the tropics and subtropics.
But at the end of the Triassic, about 202 million years ago, more than three-quarters of land and sea species were wiped out in a mysterious mass extinction event associated with vast volcanic eruptions that sent much of the world into cold and darkness. This extinction set the stage for the reign of the dinosaurs.
to write Scientific advances, an international team of researchers explains how the mass extinction helped dinosaurs dominate. They began by examining dinosaur footprints from the Junggar Basin in Xinjiang, China. These show that dinosaurs lurked along coastlines at high latitudes. By the late Triassic, the basin was well within the Arctic Circle, about 71 degrees north.
But the scientists found small pebbles in the plain sediments of the valley, which once contained many shallow lakes. The pebbles were identified as “ice-rafted debris,” meaning they were carried from lakeshores on ice sheets before falling down as the ice sheet melted.
Together, the evidence suggests that dinosaurs not only lived in the polar region, but also thrived despite the freezing conditions. Adapting to the cold, the dinosaurs were ready to conquer new territories as the dominant, cold-blooded species died out in the mass extinction.
Stephen Brussate, professor of paleontology at the University of Edinburgh, who was not involved in the research, said dinosaurs were often typecast as animals that lived in tropical forests. New research showed they were exposed to snow and ice at higher latitudes, he said.
“Dinosaurs lived in these cold, icy regions, and had to deal with snow and frost and everything that humans living in similar environments have to deal with today. So how did dinosaurs manage to do that? Their secret was their feathers,” he said.
“The feathers of these first, primitive dinosaurs would have provided a downy coat to keep warm in the high-latitude cold. These feathers seem to have come in handy when the world changed suddenly and unexpectedly, and giant volcanoes began erupting at the end of the Triassic, leaving much of the world cold and dark during repeated volcanic-winter events. overwhelmed.
