Dinosaurs have adapted to cold weather, research on the risk of extinction discovered

A new study offers what it says is the first physical evidence that dinosaurs from the Triassic period regularly endured freezing conditions, allowing them to survive and eventually displace other species on the planet. .

The study, published in the journal Science Advances on July 1, looks at the circumstances surrounding the Jurassic Extinction 202 million years ago, which killed several large reptiles and led to the eventual takeover. end of the dinosaurs.

During the extinction event, researchers say cold snaps killed many cold-blooded reptiles.

By studying footprints and rock fragments in a remote desert in the Junggar Basin in northwest China, researchers say that the Triassic dinosaurs, a relatively small group of polar bears, inhabited the polar regions. of the Earth, survived the “evolution and spread bottleneck.”

“The dinosaurs were there during the Triassic under the radar all the time,” said Paul Olsen, a geologist at Columbia University’s Lamont-Doherty Earth Observatory and lead author of the study.

“The key to their eventual dominance is simple. They’re basically cold-adapted animals. When it gets cold everywhere, they’re ready, and other animals aren’t. .”

The researchers say dinosaurs are thought to have first appeared about 231 million years ago during the Triassic period in temperate southern latitudes.

At that time, most of the land on Earth was linked together into one giant continent known as Pangea.

Dinosaurs reached the north pole about 214 million years ago, and until the mass extinction, reptiles dominated the tropical and subtropical regions of the planet.

While concentrations of carbon dioxide in the atmosphere then equal to or higher than 2,000 parts per million or five times today’s levels resulted in “intense” temperatures, researchers say climate models show high latitudes Higher elevations have experienced seasonal temperature declines and will receive less sunlight throughout the year. .

At the end of the Triassic, researchers say large volcanic eruptions that could potentially last hundreds of years killed more than three-quarters of all terrestrial and marine life on the planet.

The eruptions would also cause carbon dioxide levels in the atmosphere to rise, creating deadly temperature spikes and making seawater too acidic for many life forms.

But the eruptions will also release sulfurous aerosols, potentially deflecting sunlight and triggering a repeating decade-long “global volcanic winter,” researchers say. century and possibly longer.

The researchers say evidence suggests that many non-avian dinosaurs also had primitive feathers that were used primarily as insulation. Many dinosaurs are also thought to have been warm-blooded and highly metabolic.

“There is a stereotype that dinosaurs have always lived in lush tropical forests, but this new study suggests that higher latitudes could have been frozen and even covered with ice in the past. times of the year,” said Stephen Brusatte, professor of paleontology and evolution at the University of Edinburgh.

“The dinosaurs that lived in high latitudes happened to have winter coats [while] many of their Triassic competitors died. “

For the physical evidence to support their study, the researchers looked at the fine-grained sandstone and siltstone formations left in the sediments of the shallow ancient lake bed in the Junggar Basin, shaped formed 206 million years ago during the Late Triassic. At that point, the basin will be on the Arctic Circle.

Footprints suggest dinosaurs were present along the shoreline, while boulders about 1.5cm wide, found well away from any obvious coastline, provide evidence of “debris” icebergs,” they said.

The debris formed from the ice sheets, the researchers say, as ice accumulates on coastal land and takes away pieces of rock below.

The tape eventually separates and drifts away. As it melts, the rock falls off and mixes with the sediment.

These pebbles can be picked up during the winter when the lake’s water freezes and drifted away as the weather warms, the researchers say.

Study co-author Dennis Kent, a geologist at Lamont-Doherty, said: “This shows that these areas were regularly frozen and that the dinosaurs were doing well.”

The researchers say more work is needed to find fossils in former polar regions, such as the Junggar Basin.

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