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The tail of a 99-million-year-old dinosaur, including bones, soft tissue, and even feathers, has been found preserved in amber, according to a report published today in the journal Current Biology.

While individual dinosaur-era feathers have been found in amber, and evidence for feathered dinosaurs is captured in fossil impressions, this is the first time that scientists are able to clearly associate well-preserved feathers with a dinosaur, and in turn gain a better understanding of the evolution and structure of dinosaur feathers.

The semitranslucent mid-Cretaceous amber sample, roughly the size and shape of a dried apricot, captures one of the earliest moments of differentiation between the feathers of birds of flight and the feathers of dinosaurs. (Learn more about the evolutionary relationship between dinosaurs and birds.)

Inside the lump of resin is a 1.4-inch appendage covered in delicate feathers, described as chestnut brown with a pale or white underside.

Based on the structure of the tail, researchers believe it belongs to a juvenile coelurosaur, part of a group of theropod dinosaurs that includes everything from tyrannosaurs to modern birds.

The presence of articulated tail vertebrae in the sample enabled researchers to rule out the possibility that the feathers belonged to a prehistoric bird. Modern birds and their closest Cretaceous ancestors feature a set of fused tail vertebrae called a pygostyle that enables tail feathers to move as a single unit.

The dinosaur feathers feature a poorly defined central shaft (rachis) and appear to keel to either side of the tail. The open, flexible structure of the feathers is more similar to modern ornamental feathers than to flight feathers, which have well-defined central shafts, branches, sub-branches, and hooks that latch the structure together.