Today, animals living in Earth’s coldest regions require insulation, whether it’s a layer of fat, fur or feathers—and there’s growing data that shows dinosaurs needed that same protection, too. Now, researchers have identified the first fossil evidence that dinosaurs donned feather coats to weather the Cretaceous-era climate in the South Pole.
The conversation about which dinosaurs had feathers, which had scales or which had a mix of both is complicated. Definitely not all of them had feathers, Tyrannosaurus rex was probably at least a little scaly, but some certainly had gorgeous, occasionally colorful plumage. Finding fossilized feathers is rare because soft tissues only stand the test of time in highly specific circumstances, which is partly why the new find is so exciting.
The ten new fossilized feathers were first found in the 1960s during road construction on a hill near the Koonwarra Fossil Bed in southeastern Australia. Initially, scientists took them as evidence of ancient birds, but detailed analysis was not done until now.
“Fossils feathers have never been found in polar settings before,” lead author and paleontologist Benjamin Kear of Uppsala University in Sweden tells John Pickrell at National Geographic. The discovery “shows for the first time that a diverse array of feathered dinosaurs and flight-capable primitive birds inhabited the ancient polar regions.”
About 118 million years ago, Australia was a part of the southernmost land mass with Antarctica. However, the dinosaurs and ancient birds living at that time wouldn’t have faced the same extreme weather that the South Pole experiences today. Even still, they would have needed to survive long periods of cold and darkness in winter, according to a pre-print paper in review for the journal Gondwana Research.
The researchers analyzed feathers for morphological and chemical data, according to an Uppsala University statement. Only one of the feathers resemble the type that modern birds use for flight. True feathers have veins that are practically zippered together by barb-like structures, which is why it takes some force to push them apart. The fossil finds also included a proto-feather, which lacks those barbs, making it more hair-like and fluffy. They weren’t near any skeletal fossils, and probably fell into the Koonwarra Lake while the creature was molting.
The feathers were probably dark colored, which was unexpected in a polar region and might mean that the animals changed colors with seasons, reports Pickrell. And even though the feathers may not have been used to fly, they were probably used for warmth.
“It makes perfect sense that these feathers would have helped to keep dinosaurs and primitive birds warm at high latitudes during the Cretaceous,” Ryan McKellar, fossil feather expert who an author of the paper, tells National Geographic. “The report provides a really important snapshot of early Cretaceous polar plumage.”
The largest feather was just over half an inch long, and the smallest—which resembles bird hatchlings’ down feathers—was under a quarter inch in length. Because the majority of feathers weren’t fit for flight, they may have belonged to small, flightless carnivores from the dromaeosaur group. The Koonwarra Fossil Bed holds hints at what they might have eaten: it’s also full of fossilized fish.