About 202 million years ago, a mass extinction event wiped out three-quarters of the planet’s species, including many large reptiles. Yet the dinosaurs somehow survived and thrived.
The secret of his survival?
Fossil hunters have traced the rise of the dinosaurs back to the frigid winters the animals endured as they roamed the far north. Footprints and stone deposits from northwestern China suggest that dinosaurs adapted to the cold in the polar regions before a mass extinction paved the way for their reign at the end of the Triassic.
The key? The feathers, which would have helped the dinosaurs to keep warm, so they could cope with the cold and take better advantage of the new territories.
“Dinosaurs were there during the Triassic under the radar all along,” said Paul Olsen, a geologist at Columbia University’s Lamont-Doherty Earth Observatory and lead author of the study published in the journal Science Advances. “The key to their eventual dominance was very simple. They were fundamentally cold-adapted animals. When it was cold everywhere, they were ready and other animals were not .”
Thus, the dinosaurs’ warm layers of feathers could have helped the creatures weather relatively brief but intense episodes of volcanic winter associated with massive eruptions. The study authors say that during the extinction, cold snaps that were already occurring at the poles spread to lower latitudes, killing cold-blooded reptiles. The adapted dinosaurs survived the evolutionary bottleneck and dispersed thanks to rudimentary feathers that helped dinosaurs thrive in these occasionally inhospitable areas, providing insulation from the cold.
This is the conclusion of work based on recent excavations in the remote desert of northwest China’s Junggar Basin .
A more feasible scenario
Dinosaurs are thought to have first appeared during the Triassic Period in southern temperate latitudes about 231 million years ago, when most of the planet’s land coalesced into a giant continent geologists call Pangea. Until the mass extinction in 202 million years, the larger intermediate tropical and subtropical regions were dominated by reptiles, including relatives of crocodiles and other fearsome creatures. Then, in the Triassic extinction event, Pangea began to break apart, opening up what is now the Atlantic Ocean and separating what are now the Americas from Europe, Africa, and Asia.
Among other things, the eruptions would have caused atmospheric carbon dioxide to skyrocket beyond its already high levels , causing deadly temperature spikes on land and making ocean waters too acidic for many creatures to survive.
“Through their adaptation to low temperatures , dinosaurs were able to survive volcanic winters and thus expanded to dominate terrestrial communities for the next 135 million years,” the scientists say.
Having adapted to the cold, dinosaurs were poised to seize new territory as dominant cold-blooded species perished in mass extinction, taking over niches vacated by less hardy reptiles.
Feathers are probably just one of the many reasons dinosaurs rapidly diversified and spread throughout the world at the beginning of the Jurassic.
“There’s a stereotype that dinosaurs always lived in lush rainforests, but this new research shows that higher latitudes would have been frozen and even covered in ice for parts of the year,” said Stephen Brusatte, professor of paleontology and evolution at the University of Edinburgh. “It turns out that dinosaurs living in high latitudes already had winter coats [while] many of their Triassic competitors went extinct.”
Referencia: Paul Olsen, Jingeng Sha, Yanan Fang, Clara Chang, Jessica H. Whiteside, Sean Kinney, Hans-Dieter Sues, Dennis Kent, Morgan Schaller, Vivi Vajda. Arctic ice and the ecological rise of the dinosaurs. Science Advances, 2022; 8 (26) DOI: 10.1126/sciadv.abo6342
