66-Million-Year-Old Feather Found Inside Dinosaur Dung Offers Clues to Which Birds Survived the Extinction

A fossil the size of a cherry, pulled out of the Montana badlands in 2016, is giving paleontologists a rare window into the last days of the dinosaurs.

David DeMar, a lab manager at the Burke Museum in Seattle, found the object while doing field work in the Hell Creek Formation, according to NPR. He was crawling on his hands and knees searching the ground when he spotted a small, dark, round chunk.

"I rolled it over and I was like, 'You got to be kidding me,'" DeMar told NPR. Embedded in a crack on the surface was a tiny fossilized branching structure. It was a feather, the first ever recovered from that part of the world.

Jingmai O'Connor, an associate curator of fossil reptiles at the Field Museum of Natural History in Chicago, later joined the project to study it. "It is, without a doubt, the best feather we've ever found from the age of dinosaurs," O'Connor told NPR.

The find is described in the journal Current Biology. The feather dates to the late Cretaceous period, roughly 66 million years ago, right before the asteroid impact that triggered the mass extinction that killed off the dinosaurs and a huge share of other life on Earth.

It Was Sitting in Dinosaur Feces

The round object DeMar picked up turned out to be a coprolite, the scientific term for fossilized feces, and researchers believe a large meat-eating dinosaur produced it. "So I would argue that Tyrannosaurus rex or Nanotyrannus are the more likely candidates," O'Connor said, according to NPR. That small chunk had broken off from a few larger, softball-sized pieces where researchers say additional clues may still be found.

When the team CT-scanned the coprolite, they found more than just the one feather. Inside were additional feathers, a couple of bone fragments, and two tiny fish scales.

After studying the feathers and bones together, O'Connor concluded they likely all came from the same animal, one adapted to life in the water. She believes it was an ancient aquatic, swimming bird, "kind of like a loon or a grebe," she said. "They're foot-propelled divers."

The Extinction Survival Question

Researchers say the fossil assortment may reveal part of a late Cretaceous food web, and they speculate it could help explain why some types of ancient birds died out alongside the dinosaurs while others survived to give rise to modern birds, according to NPR.

If the bird whose feathers ended up in a predator's gut was already adapted to hunting fish in water, that same skill set could have mattered after the asteroid hit, when many land food sources collapsed but aquatic ecosystems held on better in some areas. It fits a broader pattern paleontologists have documented, where surviving bird lineages after the extinction tend to be ones with generalist or water-based diets.

But it's important to be precise about what's actually established here versus what's inference. The species identification of the aquatic bird is O'Connor's interpretation based on feather and bone structure, not a confirmed genus-and-species match. The link between this particular bird's diet and the broader survival pattern across bird lineages is described by the researchers themselves as speculation, not a settled conclusion. NPR's reporting is careful to frame it that way, quoting O'Connor's reasoning rather than presenting it as fact.

The larger, softball-sized pieces of the same coprolite that this fragment broke off from have not yet been fully examined, according to the reporting. Whatever additional feathers, bones, or scales are buried in those chunks could either strengthen or complicate the current interpretation. Until that analysis is done, the question of exactly which bird lineages survived the asteroid, and why, remains open.