The study's lead author, Lida Xing of the China University of Geosciences in Beijing, found the unusual specimen at an amber market in Myanmar in 2015, and urged the Dexu Institute of Palaeontology to buy the piece after recognizing its potential scientific importance.
The team used a CT scan to peer into the fossil, finding that the long and flexible nature of the tail meant it had to belong to a dinosaur, not a bird.
The tail belonged to a dinosaur called Coelurosaur — a dinosaur about the size of a small bird, from the same theropod group of dinosaurs as Tyrannosaurus rex. Despite the feathers, the dinosaur was not able to fly, providing more evidence for the contention that plumage originally began popping up on animals for reasons other than flight — such as for camouflage or attracting mates.
Amber is fossilized tree sap, and it acts as a kind of resin that can preserve organic matter that would otherwise be lost.
"Amber pieces preserve tiny snapshots of ancient ecosystems, but they record microscopic details, three-dimensional arrangements, and labile tissues that are difficult to study in other settings," one of the study's authors, Ryan McKellar of the Royal Saskatchewan Museum in Canada, said in a news release. "This is a new source of information that is worth researching with intensity and protecting as a fossil resource."