Paleontologists led by Jingmai O'Connor of Chicago's Field Museum have identified the best-preserved bird feather ever found from the age of dinosaurs, discovered inside a fossilized dropping (coprolite) from Montana's Hell Creek Formation. The golf-ball-sized coprolite, unearthed in 2016 by David DeMar Jr. of the University of Washington's Burke Museum, was likely produced by a T. rex or Nanotyrannus that had eaten a hesperornithiform, an ancient loon-like diving bird.
CT scanning at USC revealed multiple feathers, tiny fish scales from a gar, and bird leg bones packed inside the roughly 66-million-year-old dropping — the first feathers ever recovered from Hell Creek after more than 150 years of fossil hunting there. The feathers combine primitive, fluffy protofeather traits with more modern structures suited for diving, giving researchers a rare three-dimensional look at feather evolution right before the mass extinction.
O'Connor and colleagues, whose study appeared in Current Biology on September 10, argue that feather structure and molting patterns may explain why some bird lineages died out alongside the dinosaurs while others — the ancestors of every bird alive today — survived. Better insulation from more advanced feathers could have been the deciding factor when the asteroid struck.