Scientists have discovered the featured tail of a baby dinosaur preserved in amber. Though dinosaur feathers have been found in amber before, the discovery marks the first time bone, soft tissue and feathers have been found together.

Researchers believe the 99 million-year-old tail belonged to a juvenile coelurosaur, a kind of theropod dinosaur. The scientists described their discovery and analysis of the preserved tail in a new paper, published this week in the journal Current Biology.

The dinosaur's densely packed -- but not well-structured -- feathers weren't useful for flight; researchers hypothesize they were used for temperature regulation or communication.

The nature of the feathers and their relationship to the tail bone served as proof of the tail's owner -- a dinosaur, not a prehistoric bird.

"We can be sure of the source because the vertebrae are not fused into a rod or pygostyle as in modern birds and their closest relatives," study co-author Ryan McKellar, a curator at the Royal Saskatchewan Museum in Canada, said in a news release. "Instead, the tail is long and flexible, with keels of feathers running down each side."

The amber sample was procured by Lida Xing, a paleontologist from the China University of Geosciences in Beijing, at an amber market in Myitkyina, Myanmar, in 2015.

"I have studied paleontology for more than 10 years and have been interested in dinosaurs for more than 30 years," Xing told NPR of the initial moment of discovery. "But I never expected we could find a dinosaur in amber. This may be the coolest find in my life. The feathers on the tail are so dense and regular, this is really wonderful."

How exactly feathers evolved remains the matter of considerable debate, but the latest findings help clarify the evolutionary timeline.

The features found on the preserved tail resemble decorative feathers. Feathers used for flight typically featured a strong central shaft with branches and subbranches. The smaller subbranches feature hooks that bind the feather together.

The feathers in the amber feature hook-like shapes, but they are floppy, loosely organized and without a central stem. Thus, the latest discovery suggests the hooked barbules came first and the stronger hollow shaft came later.