Dinosaurs Thrived During A Mass Extinction Event In Freezing Temperatures: Study

When we hear about mass extinction, the first thing that comes to mind is dinosaurs and how they were completely wiped off our planet.

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However, a novel study has now revealed that dinosaurs actually outlived other creatures during a large-scale extinction event preceding the period where they became dominant due to their ability to survive extremely cold temperatures.

Dinosaurs are thought to have first made their appearance during the Triassic Period across southerly latitudes roughly 231 million-years-ago. This was a time when the whole planet was joined together, like a massive continent dubbed Pangaea.

They travelled to the far northern region around 214 million-years-ago. Until the mass extinction that happened around 202 million-years-ago, the more expansive tropical and subtropical regions in between comprised majorly of reptiles.

During this era, (which also extended to the Jurassic period), the carbon dioxide concentrations ranged over 2,000 parts per million -- roughly five times the levels today. This means the temperatures during that time would be pretty intense.

There is no evidence of polar ice caps then. Moreover, excavations have shown that forests grew in the icy polar regions of today. However, some climate change models hint that high latitude regions were cold some of the time, even with such high CO2 levels. But no physical evidence has been revealed that showed that they froze.

When Triassic ended, a brief period of a million years saw the extinction of more than three-quarters of all terrestrial and marine species on Earth. This included shelled creatures, corals and all sizable reptiles.

Creatures like turtles, and animals living in burrows survived, among a few mammals. But it isnĄ¯t clear what exactly happened. Scientists link it to a series of massive volcanic eruptions which could have lasted hundreds of years, which was also the time the Pangaea started to split.

These eruptions could have also caused atmospheric CO2 to rise to exponential levels which were already too much, to begin with. This resulted in deadly temperature spikes on land and turned ocean water acidic, making it impossible for some creatures to survive.

Researchers cite a third factor -- in the fiercest phases of the eruptions, the creatures would have released sulphur aerosols that deflected enough sunlight to repeat global volcanic winters which would have overpowered high greenhouse gas levels. Such winters would have lasted over a decade, which could have killed uninsulated reptiles, keeping cold, adapted insulated dinosaurs to remain.

Also read: No Sunlight: How Dinosaur-Killing Asteroid Wiped Off 75% Of All Life On Earth

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They claim this based on their evidence -- fine-grained sandstone and siltstone formations left by sediments in shallow ancient lake bottoms in the Junggar Basin. The sediments were formed around 206 million years ago in the late Triassic period. At this time, before the Pangaea split, the basin was at around 7u1 degrees north -- over the Arctic Circle.

Footprints found by the authors reveal that dinosaurs were present along the shorelines. Moreover, in the lakes, researchers found abundant pebbles up to around 1.5 centimetres across within the normally fine sediments which was also way far away from a shoreline. The only plausible explanation would be that they were ice-rafted debris.

Study co-author Dennis Kent, a geologist at Lamont-Doherty explained, Ą°Severe wintery episodes during volcanic eruptions may have brought freezing temperatures to the tropics, which is where many of the extinctions of big, naked, unfeathered vertebrates seem to have occurred. Whereas our fine feathered friends acclimated to colder temperatures in higher latitudes did OK."

Stephen Brusatte, a professor of paleontology and evolution at the University of Edinburgh added, "There is a stereotype that dinosaurs always lived in lush tropical jungles, but this new research shows that the higher latitudes would have been freezing and even covered in ice during parts of the year. Dinosaurs living at high latitudes just so happened to already have winter coats [while] many of their Triassic competitors died out."

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