Some birds survived the asteroid that wiped out dinosaurs. A fossilized poop can help explain why

(CNN) — Tiny feathers encased in fossilized poop are helping scientists understand why some birds made it through the mass extinction that wiped out the dinosaurs and others did not.

Unearthed in Montana, the feathery find belonged to a bird that had once been devoured and excreted by a predatory dinosaur — possibly a Tyrannosaurus rex or smaller cousin — just before the asteroid strike that unleashed the extinction event 66 million years ago, according to a new study published in the journal Current Biology. The remains include the best-preserved feather ever extracted from Mesozoic deposits, or rocks from the age of the dinosaurs, and the discovery offers a rare glimpse into a make-or-break moment for many species.

“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,” said lead study author Jingmai O’Connor, the associate curator of fossil reptiles at Chicago’s Field Museum, in a news release.

However, the stunning specimen likely represents a species that did not survive in the aftermath of the asteroid strike, according to the team behind the new research. Based on an examination of bones found with the feathers inside the coprolite — the scientific term for fossilized feces — the study authors believe the feathers belonged to a small, flightless diving bird similar to modern loons, which were part of a now-extinct group known as Hesperornithiformes.

Paleontologists established decades ago that birds evolved from dinosaurs. That means the bird species flapping around in backyards today are effectively the only surviving dinosaurs. Puzzlingly, however, today’s birds all descend from just one group of dinosaur-era birds called Neornithes, a close relative of Hesperornithiformes.

The hellish conditions triggered by the planet’s collision with the city-size space rock wiped out all other birds and dinosaurs, O’Connor noted. The newly found feathers could hold a clue to the downfall of the Hesperornithiformes.

Primitive feathers

O’Connor said some of the feathers looked highly similar to those present today in modern birds, with a central spine having a square cross section that would have helped make the feather stiff yet lightweight. However, others looked more primitive in structure — smaller and fuzzier — and would not have been as good at insulating as modern bird body feathers, she added.

“The primitive body feathers of hesperornithiforms were not a problem for these birds during the greenhouse world of the Mesozoic, but the asteroid impact triggered an impact winter and global temperatures dropped significantly,” she explained via email.

Scientists believe the collision released billions of tons of dust, sulfur and other gases into the atmosphere, blocking the sun and leading to a dramatic cooling of Earth’s climate. Plants were unable to photosynthesize, a biological process critical for life, for almost two years afterward, research suggests.

“Now the primitive body feathers and their less effective insulation is problematic — it takes more energy to stay warm but there is less food available through which to acquire this energy.”

She said a similar pattern had been seen in other birds from the Cretaceous called enantiornithines. Their plumage has been preserved in globs of amber — prehistoric tree resin.

O’Connor thinks one of the main reasons the Neornithes branch of the bird family survived the mass extinction is due to differences in their feathers. Other scientists had reasoned that because Neornithes species lived near water, something about this habitat helped protect them from the devastating effects of the mass extinction. However, Hesperornithiformes also lived by water and disappeared.

To confirm her hypothesis, paleontologists would need to find a Neornithes fossil from just before the asteroid strike and examine its plumage to confirm that it does not retain feathers with primitive traits, O’Connor said.

“It would have to be preserved in amber or in another exceptionally preserved coprolite so that the feathers are preserved in 3D and with enough bone to be certain about the identification,” she noted.

“Who knows, maybe someone has already picked up a coprolite with these traces inside.”

Rare find

Such well-preserved feather specimens don’t turn up often, and even those studied in the new research weren’t immediately apparent. David DeMar Jr., a paleontologist with the University of Washington in Seattle, came across the coprolite that preserved them in 2016 while collecting fish fossils in Montana, within the Hell Creek Formation.

Since no feathers had ever been found in the Hell Creek, despite a 150-year-history of fossil hunting there, O’Connor said DeMar’s first thought was maybe the crack in the reddish-brown nodule he found on a rocky outcrop contained a plant. But closer inspection revealed it was a feather.

“I picked it up and scanned its surface through my hand lens, and that’s when I couldn’t believe what I was seeing, a tiny fossil feather,” DeMar, who is a coauthor on the study, said in the news release.

However, it wasn’t until the researchers imaged the fossilized feces in a micro-CT scanner that they realized the specimen contained multiple feathers, leg bones and even remnants of the bird’s stomach contents. Many of the remains were exceptionally preserved in three dimensions.

The fossilized dinosaur droppings also preserved two minuscule, diamond-shaped scales from a fish known as a gar that still exists today. The fish would have been too small to satisfy a dinosaur predator and thus probably formed the bird’s last meal before it was wolfed down by the T. rex, according to the study.

“If it wasn’t for the break exposing the feathers, we’d still be unaware that coprolites can be a source of this kind of information,” O’Connor said.

“I continue to marvel over the kinds of things we find in the fossil record that were never thought possible,” said Anthony Fiorillo, adjunct faculty research professor at Southern Methodist University and the executive director of the New Mexico Museum of Natural History & Science, who was not involved in the research.

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