Dinosaurs adapted to the cold before mass extinction, say scientists

Fossil hunters have traced the rise of the dinosaurs back to the freezing winters the beasts endured while roaming around the far north.

Footprints of the animals and stone deposits from north-west China suggest that dinosaurs were adapted to the cold in polar regions before a mass extinction event paved the way for their reign at the end of the Triassic.

The dinosaurs were better able to cope with a covering of fuzzy feathers to keep them warm, and to take advantage of new territories when brutal conditions wiped out great swaths of more vulnerable creatures.

The key to their eventual dominance was very simple, said Paul Olsen, lead author of the study at the Lamont-Doherty Earth Observatory at Columbia University. They were fundamentally cold-adapted animals. When it got cold everywhere, they were ready, and other animals were not. The first dinosaurs are thought to have emerged in the temperate south more than 230 m years ago when most of Earth s land made up a supercontinent called Pangaea. The dinosaurs were initially a minority group, living mainly at high altitudes. Other species, including the ancestors of modern crocodiles, dominated the tropics and subtropics.

More than three-quarters of land and marine species were wiped out in a mysterious mass extinction event that sent much of the world into cold and dark at the end of the Triassic, about 202 m years ago. The devastation set the stage for the reign of the dinosaurs.

An international team of researchers wrote in Science Advances how mass extinction may have helped the dinosaurs rise to dominance. They began by examining dinosaur footprints from the Junggar Basin in Xinjiang, China. These findings showed that dinosaurs lurked along shorelines at high latitudes. The basin was well within the Arctic Circle, about 71 degrees north of the late Triassic.

The scientists also found small pebbles in the fine sediments of the basin, which once held several shallow lakes. The pebbles were identified as ice-rafted debris, meaning they were carried away from the lakesides on sheets of ice before falling to the bottom when the ice melted.

The evidence shows that the dinosaurs did not only survive in the polar region, but thrived despite freezing conditions. After adapted to the cold, the dinosaurs were poised to take over new territories as dominant, cold-blooded species perished in mass extinction.

Stephen Brusatte, a professor of paleontology at the University of Edinburgh, who was not involved in the research, said dinosaurs were often typecast as beasts that lived in tropical jungles. He said that the new research showed that they would have been exposed to snow and ice at high latitudes.

Dinosaurs would have had to deal with snow and frostbite and all the things that humans living in similar environments have to deal with today, even though they would have lived in these frigid, icy areas. Their secret was their feathers, he said.

The feathers of these first primitive dinosaurs would have provided a downy coat for keeping them warm in the high-latitude chill. It seemed that these feathers came in handy when the world suddenly changed and giant volcanoes began to erupt at the end of the Triassic, plunging much of the world into cold and dark during repeated volcanic-winter events.