Dinosaurs ruled because they could withstand cold.

Ancient footprints indicate dinosaurs' capacity to withstand chilly conditions.

Dinosaur traces in sandstone and siltstone of ancient lake beds in the Junggar Basin of northeastern China imply the reptiles had acclimated to the arctic areas more than 200 million years ago

Dinosaurs originally arose in temperate southern latitudes during the Triassic epoch, when Earth's continents were still connected to create Pangea.

By 214 million years ago, dinosaurs had migrated to the Arctic, but they were still a tiny group compared to other animals, such as the progenitors of current crocodiles.

"Dinosaurs were present throughout the Triassic beneath the radar all the time," lead author Paul Olsen remarked

"Their supremacy was easy. Cold-adapted animals. Other animals weren't ready for the winter, but they were."