Scientists have discovered a feathered dinosaur tail trapped in a piece of 99-million-year-old amber, bought from an amber market in Myanmar. The specimen is definitive proof that two-legged dinosaurs like Tyrannosaurus rex had bird-like feathers.
While a dinosaur-era feather had been found embedded in amber in 2011 and again in June 2016, those small specimens preserved just isolated plumage, so researchers were not able to say with certainty whether it belonged to an ancient bird or a dinosaur. The most recent find has preserved the animal’s tail: eight pieces of vertebrae covered with soft tissue and plumage. From CT scans and microscopic observation, paleontologists concluded the amber dates back 99 million years, to the mid-Cretaceous period, and the tail belonged to a dinosaur, and not a prehistoric bird.
The research, published today in the journal Current Biology, is based on a piece of amber spotted and purchased in 2015 by Lida Xing, from the China University of Geosciences in Beijing, at an amber market near Myitkyina, in the Kachin State of northeastern Myanmar.
The amber preserved the dinosaur’s tail in 3D, offering much more information than a fossil specimen would. The tail forms a small curl and measures about 3.67 cm in length, with about 2 cm of bones. The researchers believe it belonged to a juvenile coelurosaur. “If we extrapolate from the piece of tail we’ve got, it would have been the size of a sparrow,” says Ryan McKellar, the curator of invertebrate paleontology from the Royal Saskatchewan Museum in Canada who participated in the research.
But the sparrow-sized dinosaur probably could not fly, because its feather don’t have rigid shafts, but a soft plumage structure instead. Pigmentation suggests the tail is pale or white underneath, while the top would be chestnut brown in color, says McKellar. It’s uncertain how the colors might have changed over time, or what color the rest of the dinosaur would have been. But the two shades of the tail suggests an animal with a white belly and dark-colored back.
For a long time, dinosaurs were thought to be a relative of scaly lizards, but researchers have found more and more evidence in the past two decades showing that many species had feathers or plumage. A current exhibition at the American Museum of Natural History in New York, Dinosaurs Among Us, presents extensive fossil evidence that feathered dinosaurs have evolved into modern birds, and therefore aren’t really extinct.
“I think at this point the number of specimens we’ve seen to date point to the fact that most theropod dinosaurs probably had plumage or feathers at some point in their life, [although] may not have been all the way through to adulthood,” says McKellar. “It’s basically one half of the [dinosaur] family tree.”
The Myanmar amber deposit is one of the largest in the world, producing over 10 tons of amber a year; most other mines produce one or two kg annually. The research team is currently working with sellers from the Myanmar market to intercept amber specimens before they fall into private collections.
“I’d love to see a larger sample size, either a more complete individual, where you get the entire specimen, or most of the specimen,” McKellar says. ”It’d be a game changer in terms of how we see the animals.”