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

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. 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. 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.