Dinosaur dung feathers reveal why certain ancient birds perished
Discovery in Montana’s Badlands
The specimen was unearthed in 2016 by vertebrate paleontologist David DeMar Jr. of the University of Washington and the Burke Museum. He spotted a dark, reddish-brown nodule while collecting fossils in the badland exposures of eastern Montana. Initial field inspection with a hand lens revealed a single tiny feather protruding from the surface.
Subsequent micro-CT scanning at the University of Southern California’s medical campus digitally stacked thousands of X-rays. This exposed a complex arrangement of multiple feathers, tiny gar fish scales, and leg bones belonging to a hesperornithiform, an extinct group of toothed, flightless diving birds ecologically similar to modern loons.
Micro-CT Scans Reveal Dual Morphology
Lead author Jingmai O’Connor, vertebrate paleontologist at the Field Museum of Natural History in Chicago, noted that the preservation rivals specimens recovered from amber deposits. The analysis indicates a dual morphological structure within the plumage.
Dense bristles observed on the specimens suggest traits capable of repelling water effectively, comparable to the plumage of modern pelicans. Micro-CT imaging revealed that the central shafts of these feathers contain air pockets—a structural adaptation that maintains lightweight rigidity necessary for flight.
Insulation Deficiencies and Mass Extinction
Despite these specialized aquatic adaptations, the specimens also retained primitive, stringy down characteristics similar to the plumage of non-avian dinosaurs. According to the research team, this morphological combination likely provided inferior thermal insulation compared to the advanced plumaceous feathers found in the ancestors of modern birds, known as Neornithes.
When a massive asteroid impact triggered a global cooling event approximately 66 million years ago, wiping out roughly 75 percent of life on Earth, this deficiency in thermal regulation may have proved fatal. While modern bird ancestors possessed the advanced insulation required to endure the prolonged dark winter, hesperornithiforms and enantiornithines lacked adequate cold-weather protection.
Unlocking Trophic Interactions Through Coprolites
Co-author Gregory Wilson Mantilla, a University of Washington biology professor and curator of vertebrate paleontology at the Burke Museum, emphasized that finding these remains inside predator coprolites offers a rare window into ancient trophic interactions alongside avian evolution.
Because fossilized feathers remain exceptionally scarce in the geological record, researchers stress that examining coprolites could expand the availability of intact Mesozoic specimens for future comparative studies.
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