Paleontologists have found the first feathers ever preserved inside fossilised dinosaur poop. The discovery may explain why only some ancient birds survived the asteroid impact 66 million years ago.

The study was published on September 10, 2026, in Current Biology. It was led by Jingmai O’Connor of the Field Museum in Chicago.

The coprolite was found in 2016 in Montana’s Hell Creek Formation by David DeMar Jr. It came from a large meat-eating dinosaur, possibly a young Tyrannosaurus rex or Nanotyrannus. Inside were feathers, tiny fish scales and bone fragments from a hesperornithiform, an extinct group of diving birds.

The feathers are the best-preserved ever found from the Mesozoic era. Some resemble modern bird feathers, with square shafts filled with air pockets. Dense bristles suggest they could repel water as well as a pelican’s plumage.

But smaller, fuzzier body feathers looked more primitive. The researchers propose that weaker insulation made these birds vulnerable to the impact winter that followed the asteroid strike.

Only the ancestors of modern birds, the Neornithes, survived. Their superior plumage may have given them a crucial advantage in the drastic global cooling.