Dinosaurs took over the planet thanks to their amazing ability to endure low temperatures, according to Alternative Science, citing LiveScience.
Dinosaur footprints, sealed in the sandstone and siltstone of ancient lakes in the Junggar Basin in northwest China, suggest that reptiles thrived in the polar regions more than 200 million years ago, although the subsequent ice age led to the mass extinction of ancient animals.
Dinosaurs first appeared in the temperate southern latitudes about 231 million years ago, during the Triassic period – 252 – 201 million years ago. Then the continents of the Earth were still united into one whole – the supercontinent Pangea.
30 million after their appearance, part of the dinosaurs migrated to the Arctic regions, but they were still an insignificant group compared to other inhabitants of the Earth – the ancestors of modern crocodiles that lived in the tropics and subtropics, scientists report in a new study.
At the time of Pangea, the Dzungar basin was located at about 71 latitude, quite far from the Arctic Circle.
A little later, during the Triassic-Jurassic extinction, a chain of powerful volcanic eruptions abruptly cooled the planet, destroying more than 75% of the species. The ecological niche was vacated, and the Jurassic period is considered to be the era of ancient reptiles.
The study was published July 1 in the journal Scientific Advances.
Dinosaurs Survived Well in the Cold Polar Regions
“Dinosaurs existed throughout the Triassic period,” says lead author Paul Olsen, professor of biology and paleoecology at Columbia University’s School of Climate.
“The key to their ultimate dominance was very simple. They were cold-adapted animals. When the cold came, they were ready, other animals were not.”
Paw prints along the shorelines of former shallow lakes have confirmed the rapid expansion of dinosaurs during prehistoric global cooling.
The researchers also found small pebbles in the usually fine-grained sediments, which they identified as rocky material left behind by ice floes during summer thaws.
“These regions were constantly freezing, but the dinosaurs were doing just fine,” said study co-author Dennis Kent, senior scientist and geologist at Columbia University’s Lamont-Doherty Earth Observatory.
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The data obtained by the researchers indicate that dinosaurs did not just survive in frosty weather – they thrived in it, which allowed them to become the undisputed rulers of the planet by the end of the Triassic period.
But how did it happen?
Previous research has shown that many groups of dinosaurs were warm-blooded and had high metabolisms. Also, many dinosaurs living on the African, European and American continents had a special type of thermal insulation – feathers.
“Severe winter periods during volcanic eruptions could bring low temperatures to the tropics, and it is there that the extinction of large, naked, non-feathered vertebrates seems to have occurred,” says Kent. “At the same time, our beautiful feathered friends, adapted to more cold temperatures in higher latitudes, coped with low frosts”.
The researchers’ findings refute the popular notion of dinosaurs as animals that could only survive in warm climates, Stephen Brusatte, professor of paleontology and evolution at the University of Edinburgh, who was not involved in the study, said in a statement.
“There is a stereotype that dinosaurs have always lived in lush tropical jungles, but this new study shows that it could get quite cold at higher latitudes,” Brusatte explains.
“It so happened that the dinosaurs that lived in high latitudes already had winter coats, while many of their competitors from the Triassic period died out.”
Now that the researchers have documented signs of survival in cold regions, they plan to look for harder-to-find fossils in regions that were once polar regions.
“Most paleontologists are attracted to the late Jurassic period – we hope to find a lot of large skeletons,” says Olsen. “The paleoarctic is practically ignored.”