A 66-Million-Year-Old Feather Trapped in Dinosaur Poop Might Help Explain Why Some Birds Survived Mass Extinction

Discovered in Montana in 2016, the cherry-size coprolite contains feathers, bones and evidence of the bird’s last meal before the creature was eaten by a theropod

Sarah Kuta | Daily Correspondent

September 16, 2026 2:45 p.m.

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

In 2016, paleontologist David DeMar Jr. was searching for fossils in northeastern Montana when he discovered a small, broken piece of fossilized dinosaur poop. As he took a closer look, DeMar was shocked to discover a tiny, well-preserved feather embedded in the cherry-size coprolite.

“I couldn’t believe what I was seeing,” DeMar, a collections manager at the University of Washington’s Burke Museum of Natural History and Culture, tells New Scientist’s Christa Lesté-Lasserre.

Now, DeMar and his colleagues have analyzed the 66-million-year-old fossilized feather, which offers a rare glimpse into the birds that lived alongside the dinosaurs. Their findings, published September 10 in the journal Current Biology, could help explain why some birds survived the mass extinction event that killed all non-avian dinosaurs while others perished.

Scientists used non-invasive and non-destructive methods to analyze the fossilized dung, including micro-CT scans and 3D surface scans. These techniques revealed two bone fragments that likely came from a hesperornithiform, a flightless, short-winged aquatic bird that was similar to a modern-day loon or grebe.

Hesperornithiforms were related to neornithes, the group of birds that survived the mass extinction 66 million years ago and ultimately gave rise to all birds alive today. But hesperornithiforms belonged to a separate branch of the bird family tree and died out during the same mass extinction that wiped out the dinosaurs.

The coprolite, which researchers suspect came from a Nanotyrannus or young Tyrannosaurus rex, also contained multiple feathers and feather fragments. It’s the first time scientists have ever discovered such exquisite plumage in a coprolite.

“There are quite a few fossils that show feathers, but most of the time you’re just looking at impressions of feathers … the actual feather is not there,” Steven Salisbury, a paleontologist at the University of Queensland in Australia who was not involved with the study, tells Jacinta Bowler of the Australian Broadcasting Corporation. “This is cool because it’s actually the preserved feather in 3D.”

The primary feather, which measures about 0.37 inches long, appears to have been water-repellent. Researchers also found a smaller feather that they think came from the bird’s wing.

Both feathers have square shafts with lightweight, sponge-like cores encased in harder outer layers, a combination of features found in living birds and their immediate ancestors. In fact, researchers had never seen this structure in any other feather from the Mesozoic era, which spanned 66 million to 252 million years ago. The next-oldest known example of a sponge-like feather core is roughly ten million years younger than the specimens found in the coprolite.

The analysis also revealed two smaller, fuzzy body feathers that were more primitive in nature. These feathers, which likely helped insulate the birds from the cold, might be the key to why hesperornithiforms did not survive the mass extinction event.

Exactly how the Chicxulub impact some 66 million years ago triggered so many deaths worldwide remains the subject of scientific debate. But under one possible scenario, researchers think the asteroid strike sent enormous amounts of dust, sulfur and soot into the atmosphere, where they blocked sunlight and plunged Earth into a global winter.

During this prolonged period of cold and darkness, plants were unable to photosynthesize, and as a result, many animals starved to death. The feathers suggest some creatures may also have died because they simply couldn’t withstand the cold temperatures. The fluffy body feathers the researchers found in the coprolite might have been “good enough to keep [the birds] warm during the greenhouse world of the Mesozoic, but not good enough to keep them warm during this environmental catastrophe that was triggered by [the Chicxulub] impact event,” lead author Jingmai O’Connor, a paleontologist and associate curator of fossil reptiles at the Field Museum in Chicago, tells New Scientist.

Embedded in the coprolite, scientists also discovered two small fish scales that likely came from a gar. The fish was probably the bird’s last meal, consumed shortly before the bird itself was swallowed by the dinosaur that produced the coprolite, according to the team.

“A dinosaur ate an aquatic bird that ate a particular type of fish,” Julia Clarke, a paleontologist at the University of Texas at Austin who was not involved with the research, tells NPR’s Ari Daniel. It’s “almost like they’ve discovered a Cretaceous turducken,” a dish featuring a chicken stuffed inside a duck stuffed inside a turkey.

Jokes aside, Clarke is not convinced that the body feathers preserved in the coprolite are enough to explain the fate of birds during the mass extinction. “It’s a stretch to explain the survivorship of some [species] and the extinction of others from that evidence,” she says.

Zooming out, the study suggests that coprolites may be a largely untapped source of information about ancient birds and the creatures that ate them. Scientists may want to take another look at any fossilized feces already sitting in museum collections.

Very few animals are capable of digesting keratin, the tough, fibrous material that makes up bird feathers, so “it is reasonable to expect that feathers might be common in feces,” study co-author Karen Chin, a paleontologist at the University of Colorado Boulder, tells National Geographic’s Riley Black.

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.