A 66-million-year-old feather from an extinct bird was found inside fossilized dinosaur feces from Montana's Hell Creek Formation, marking the first feather ever identified in a coprolite.
Micro-CT scans showed the coprolite also held multiple feathers, fish scales and small bird leg bones, suggesting a predator—possibly Tyrannosaurus rex or Nanotyrannus—ate a bird that had already eaten fish.
The feather, preserved in 3D rather than as an impression, is thought to belong to a hesperornithiform, an aquatic flightless bird closely related to modern birds but wiped out in the end-Cretaceous extinction.
Researchers say that difference may help explain survival 66 million years ago: hesperornithiforms appear to have lacked the full modern plumage suite that may have given crown birds better insulation.
The team called the find a prompt for museums and scientists to CT-scan more coprolites, arguing fossilized feces could open a new source of rare soft-tissue evidence.