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It's almost impossible to discuss dinosaurs without mentioning the fact they're no longer with us (well, unless you count birds), having gone extinct at the end of the Cretaceous period when a massive asteroid struck the planet around 66 million years ago.
But long before that, the dinosaurs were the survivors of another extinction event that wiped out most of the planet's species around 202 million years ago. Occurring right at the end of the Triassic period, the Triassic-Jurassic extinction event was a series of enormous volcanic eruptions that significantly cooled the planet, dooming 75% of all land-dwelling and ocean-dwelling species. Prior to this event, large cold-blooded crocodilians were the dominant form of life, though dinosaurs had already begun to emerge around 231 million years ago.
Now, the discovery of footprints in the Junggar Basin in northwestern China provides indisputable evidence that dinosaurs were adapted to regularly freezing temperatures, explaining how they were able to survive the planet's dramatic cooling phase and eventually dominate the prehistoric landscape. In the Triassic, this region of Pangea was located firmly within the Arctic Circle, at about 71 degrees north. Many dinosaurs were warm-blooded and covered in insulating feathers, which kept them warm even in polar regions. So they were well-suited for the planet to experience a cooling event, unlike many other animals.
Dinosaurs in the snow:
- These footprints aren't the only evidence that dinosaurs lived in the paleo-Arctic, but researchers hope to find many more fossils that show how dinosaur species thrived even as their homes froze.
- The findings contradict our image of dinosaurs living in steamy jungles. And while dinosaurs did eventually inhabit tropical and subtropical regions, it was their adaptations to the cold that allowed them to survive the Triassic-Jurassic extinction event and spread across the globe.
- "The key to (the dinosaurs') eventual dominance was very simple. They were fundamentally cold-adapted animals. When it got cold everywhere, they were ready, and other animals weren't," said geologist and study lead author Paul Olsen of Columbia University's Lamont-Doherty Earth Observatory.