About 66 million years ago, a large dinosaur, possibly a T. rex or Nanotyrannus, swallowed a bird. Remarkably, evidence of that ancient meal survived in fossilized feces, preserving what researchers describe as the finest feather specimen yet discovered from the age of dinosaurs. By examining that feather, scientists say they may have uncovered an important clue to why birds became the only dinosaur lineage to survive the mass extinction at the end of the Cretaceous Period.
The findings were reported in Current Biology. "It's such a beautiful, well-preserved feather, from such an unexpected source, and it's exciting that it could help us answer this huge question in paleontology," says Jingmai O'Connor, the lead author of the new paper and the associate curator of fossil reptiles at the Field Museum in Chicago. Birds are a highly specialized branch of the dinosaur family tree, with a history stretching deep into the Mesozoic Era.
The oldest known bird, Archaeopteryx, lived about 150 million years ago. Birds then continued evolving alongside other dinosaurs for nearly another 100 million years. That long coexistence changed dramatically 66 million years ago, when an asteroid struck Earth and triggered a global mass extinction.
Nearly every dinosaur lineage disappeared, including most types of birds. One branch, however, survived. Known as Neornithes, this group ultimately gave rise to every bird species alive today.
Why Neornithes endured while other birds and dinosaurs vanished remains one of paleontology's enduring puzzles. O'Connor has spent years studying fossil birds in search of an explanation. This study, however, took her into unusual territory: feathers preserved inside fossilized feces, known as coprolites.
"As far as I know, no one has ever thought to look for feathers or to study feathers in coprolites, so this project was really exciting," says O'Connor. The specimen was discovered in 2016 by David DeMar, Jr., a research scientist and the Hell Creek Project collections manager at the University of Washington Burke Museum and co-author of the paper. DeMar was conducting fieldwork in northeastern Montana when an unusual rock caught his attention.
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