Lida Xing, a palaeontologist at the China University of Geosciences in Beijing, looked closer and saw feathers. Attached to a tail. Attached to a dinosaur that had been dead for 99 million years.

Somebody was about to turn it into jewellery.

Xing persuaded the Dexu Institute of Palaeontology to buy the piece instead, as reported by NPR. He told CNN that he doubted the trader grasped what was in his hand, and that the price never went up.

What was actually in the lump

About 36 millimetres of tail. Eight vertebrae, each no bigger than a grain of rice, joined in sequence and wrapped in skin, soft tissue and dense plumage, with a couple of ants and a beetle trapped nearby.

Feathered dinosaurs have been known since the 1990s, but almost always as impressions squashed flat in sedimentary rock, a process that flattens three-dimensional structure into a smear. Resin does the opposite. It sets around an object and holds the arrangement in place.

Xing’s team put the specimen through CT scanning and microscopy, catalogued it as DIP-V-15103, nicknamed it Eva, and published the description in Current Biology in December 2016, with co-authors from the Royal Saskatchewan Museum, the University of Bristol and the University of Alberta.

Eva was a juvenile coelurosaur, part of the branch of two-legged meat eaters that eventually produced birds, and roughly sparrow-sized when it died. Given a better afternoon, it would have grown to something a little shorter than an ostrich.

How they knew it was not a bird

Feathers in amber had turned up before. Pinning them to a known animal was the hard part, because a loose feather tells you little about its owner.

Modern birds and their closest Cretaceous relatives carry a pygostyle, a set of fused tail bones that lets the tail feathers swing as one unit. Eva’s vertebrae are separate and flexible, ruling out a bird and placing the specimen among non-avian theropods, National Geographic reported at the time.

Ryan McKellar of the Royal Saskatchewan Museum, a co-author on the paper, described it as a thin, whip-like tail closer to a mouse’s than a bird’s, fringed with feathers down both sides.

Feathers that were no use for flying

A bird feather is built around a stiff central shaft called the rachis. Barbs branch off the shaft, barbules branch off the barbs, and the barbules hook together to make the smooth surface that pushes against air.

Eva has both tiers of branching. What it barely has is the shaft, which suggests the fine branching came first and the stiff spine arrived later, as Cell Press set out in announcing the study.

One tail from one juvenile animal is a data point, not a verdict on how feathers evolved.

It is a suggestive one. Jakob Vinther, a palaeobiologist at the University of Bristol who had no part in the research, told NPR that barbules are what produce the metallic shimmer on a hummingbird or a peacock. If barbules arrived that early, he argued, small dinosaurs may have been flashing colour long before anything in the lineage could fly.

Chestnut on top, pale underneath

Colour survived as well. Analysis of the plumage put a chestnut brown across the upper surface and something pale or white underneath, the countershading carried by plenty of small animals today.

Beneath the feathers, the carbonised soft tissue held traces of ferrous iron, read by the authors as vestiges of haemoglobin. Some fragment of the animal’s blood chemistry may have stayed where it fell.

Where the amber comes from

Every one of those details reached science through a shop counter. That route has since become a problem.

Kachin State amber is dug out of ground that has been fought over for decades. Myanmar’s military seized control of the main mining district in June 2017, and in April 2020 the Society of Vertebrate Paleontology wrote to journal editors calling for a moratorium on publishing material acquired after that date. Science later covered an analysis of 937 amber papers in Communications Biology whose authors tie a steep climb in publication numbers from 2014 onward to the conflict economy feeding the mines.

Eva changed hands in 2015, on the early side of every line drawn since.

Nobody planned that. The amber coming out of Kachin now arrives with a question the fossils cannot answer by themselves, and the field has yet to agree on who should.