An extraordinary collection of ancient feather fragments preserved in amber has opened a window into a lost world, one that now appears populated by dinosaurs covered in plumage as rich and varied as that of modern birds. The feathers date to the end of the Cretaceous, about 85 to 70 million years ago. At that time, the forerunners of birds were well on their way to taking wing; dinosaurs like Epidexipteryx and Limosaurus, discovered in China in the last decade and dating to approximately 160 million years ago, possess relatively bird-like bone structures and hints of what might have been feathers. Those hints have been interpreted -- and given life in eye-popping artist renditions -- as feathers, an interpretation that was plausible but still inconclusive. But the latest fossils, found in Alberta and described Sept. 16 in Science, leave little doubt. The age of dinosaurs was a feathery one. "These lovely specimens of significantly older, smaller dinosaurs from China have got some sort of covering about them. But you can't tell if it's hair or feathers because the fossils have undergone the ravages of time," said paleontologist Alex Wolfe of the University of Alberta, a co-author of the new study. "Those fossils don't preserve the kind of detail that we have in amber, which doesn't fossilize but entombs an object." On the following pages, Wired.com looks at the new trove of feathers. Above: Feathers in Amber *Image: McKellar et al./*Science

How the Fossils Formed Amber is fossilized tree resin. Eighty million years ago, what's now the dusty plains of Alberta was the swampy, forested edge of a great inland sea, in some ways resembling the modern Everglades. "Imagine a conifer tree that's exuding droplets of resin. Before the resin hardens, it's sticky," said Wolfe. "Insects landing in and around the trees get entombed. Various vertebrates are also brushing up against this material. Imagine you walk up to the tree, put your arm up to it and pull it off, and a few hairs adhere. Then the tree produces another drop of sap, the hair becomes entombed, and 70 million years later a paleontologist comes along and finds it in a coal deposit." The new fossils accumulated in just such fashion, "when the tip of a feather broke off as a dinosaur brushed against the tree," piece by coincidental piece over millions of years, said Wolfe. Above is a picture of a feather caught in a spiderweb. *Image: McKellar et al./*Science

Primitive Structures "The least spectacular of these specimens have either single fibers or tufts of fibers coming from a common base," said Wolfe. "They've basically been inferred to exist from a theoretical model of feather evolution, but have never before been documented in the flesh, as it were." *Image: McKellar et al./*Science

Original Purposes "These simple feathers clearly had nothing to do with flight, and probably had everything to do with thermal regulation. They were essentially a feather homologue of fur," said Wolfe. Above: Sinosauropteryx Artist Lida Xing's rendition of Sinosauropteryx, the first dinosaur found with what appeared to be feathers -- an interpretation supported by the latest findings. The dinosaur wasn't represented in McKellar and Wolfe's collection, but they've used this image during presentations to illustrate how early feathers likely appeared. *Images: 1) McKellar et al./*Science 2) Lida Xing

Diving Coils "These coils are homologous with what's found now in shorebirds and aquatic birds. They create the capillary actions used to retain water, to keep cool in the summer or to make it easier for them to dive," said Wolfe. *Image: McKellar et al./*Science

Modern Structures "If these didn't come from a geological context 70 to 80 million years old, you'd think they were dead ringers for modern birds," said Wolfe of the hook-like structures above at right, which connect the stiff hairlike branches that line the shafts of flight feathers. At left is a feather from a chicken. *Image: McKellar et al./*Science

A New Richness "We not only had organisms with the most primitive feather structures, but they were living alongside organisms with far more evolved feather structures," said Wolfe. Discovering them together "forces us to reevaluate things, not just from the dinosaur end but from the avian end as well," he said. "It seems that feather evolution 80 million years before present was already quite advanced." *Image: McKellar et al./*Science

Accidental Discovery When study co-author Ryan McKellar first looked at the amber, the University of Alberta paleontologist wasn't even interested in feathers. He was interested in insects. It was only when he and Wolfe noticed odd, hair-like structures that they wondered if something other than bugs might be preserved. *Image: McKellar et al./*Science