Dinosaur tail preserved in amber, with feathers

In a golden chunk of 99-million-year-old amber, paleontologists have spotted something extraordinary: a tiny dinosaur tail with pristinely preserved feathers.

At a shade under 37 millimeters, about the length of a matchstick, the tail curves through the amber, eight full sections of vertebrae with mummified skin shrink-wrapped to bone. A full-bodied bush of long filaments sprouts along the tail’s length, researchers report December 8 in Current Biology. 

It’s “an astonishing fossil,” writes study coauthor Lida Xing of the China University of Geosciences in Beijing and colleagues. Researchers have found Cretaceous feathers trapped in amber before, but the new find is the first with clearly identifiable bits of dinosaur included. The tail bones of the new fossil gave Xing’s team a clue to the dinosaur’s identity. It may have been a young coelurosaur that looked something like a miniature Tyrannosaurus rex.

Unlike dinosaur feathers pressed flat into rock, feathers in amber can offer more information about structure, the authors suggest. In amber, “the finest details of feathers are visible in three dimensions,” Xing and colleagues write.

The little dinosaur’s feathers lack a well-developed rachis, the narrow shaft that runs down the middle of some feathers, including those used by modern birds for flight. Instead, the dino’s feathers may have been ornamental, the authors say. Microscopy images suggest that the feathers were chestnut brown on top, and nearly white underneath.