Paleontologists have discovered remarkably preserved feathers from an ancient aquatic bird inside a 66-million-year-old fossilized dinosaur dropping, according to a study published September 10, 2026, in the journal Current Biology. The cherry-sized, dark reddish-brown nodule—scientifically known as a coprolite—was collected in 2016 by David DeMar Jr., collections manager of the Hell Creek Project at the University of Washington’s Burke Museum of Natural History and Culture.
Dinosaur Coprolite Yields Rare 66-Million-Year-Old Bird Feathers
DeMar discovered the specimen while crawling across a rocky outcrop in northeastern Montana while hunting for fish fossils. Inspecting the small nodule through a hand lens, he spotted a tiny fossilized feather on the surface. Researchers identified the predator that produced the coprolite as a large carnivorous dinosaur, possibly a T. rex or Nanotyrannus.
Advanced Scans Reveal Hidden 3D Feather Preservation
Before the specimen reached a laboratory for detailed study, it underwent mineral analysis and a micro-CT scan at the University of Southern California’s medical campus. Nate Carroll, a co-author of the paper and a paleontologist at the Carter County Museum in Ekalaka, Montana, noted that running the sample through the scanner revealed the full feathery fabric in stunning 3D detail. The scans uncovered multiple feathers, tiny scales from a gar fish, and leg bones belonging to a bird.
The leg bones identified the original owner of the feathers as a hesperornithiform, an extinct group of flightless diving birds ecologically comparable to a modern loon or grebe. These birds hunted underwater, propelled by powerful hind legs. The discovery marks the first time hesperornithiform feathers have ever been identified.
An Evolutionary Middle Ground in Plumage
The recovered feathers displayed an unusual combination of modern and primitive traits. Two of the specimens, including the one visible on the surface of the coprolite, featured a rectangular-in-cross-section feather shaft with a sponge-like internal center. According to Dr. DeMar, no other Mesozoic feather has exhibited this combination of features, with the next-oldest known record of that spongy structure coming from the Early Eocene of Denmark, approximately 10 million years younger than the Hell Creek Formation fossil.
Alongside those modern-looking, water-resistant feathers, the coprolite preserved smaller, fuzzy, and more primitive down feathers typically associated with non-avian dinosaurs and enantiornithines. This unique mix makes hesperornithiforms an evolutionary middle ground between archaic dinosaur-era plumage and the insulating feathers of modern birds.
Clues to the End-Cretaceous Mass Extinction
The discovery offers a fresh perspective on a long-standing puzzle in paleontology: why birds were the only dinosaurs to survive the asteroid impact at the end of the Cretaceous Period 66 million years ago. A widely discussed hypothesis suggested that surviving ancestors of living birds, known as Neornithes, endured because they lived near water, which somehow buffered them from the worst effects of the impact. However, hesperornithiforms also lived in aquatic habitats and ultimately went extinct.
Jingmai O’Connor, lead author of the paper and associate curator of fossil reptiles at the Field Museum in Chicago, suggests that the types of feathers these birds possessed, and how they molted them, may explain why some lineages died out while Neornithes survived to produce every bird species alive today.
