When an asteroid collided with Earth 66 million years ago, spewing clouds of dust into the air and creating hellish conditions for every living thing on the planet, all the large dinosaurs perished. Birds, however, somehow made it through to the other side—and obviously continue to populate our modern ecosystems. A paper published today in the journal Current Biology reported evidence for why birds were the only group of dinosaurs to survive.
Paleontologists from the U.S. and China formed a hypothesis based on a fossilized poop, or coprolite, from a theropod dinosaur, found in Montana. Inside the poop were tiny, perfectly preserved feathers, fish scales, and leg bones, which provided critical clues in the story of bird survival.
Read more: “Dinosaurs May Have Been Literally Charbroiled After the Asteroid Impact”
“I usually work with fossils that are preserved in big stone slabs, and the entire skeleton and even the soft tissue is preserved—they make it easy for me,” explained lead study author Jingmai O’Connor, a vertebrate paleontologist at the Field Museum in Chicago, in a press release. “But with this project, we just had this coprolite—and its contents—to go off of, and it made me feel like a detective, piecing together all these little clues.”
CT scans of the reddish-brown dinosaur poop, about the size of a golf ball, revealed layers of feathers alongside scales identified as belonging to a fish in the ancient gar lineage. The delicate leg bones proved to be from a hesperornithiform, an aquatic fishing bird that resembled a loon and that perished in the mass extinction. The coincidence of evidence suggested that the feathers also belonged to this diving bird, whose final meal was a gar.
This first-ever analysis of hesperornithiform feathers illuminated features that set them apart from the birds that made it through the asteroid crash: the Neornithes. “Some of these diving birds’ feathers seem to have been modern-looking and waterproof, but they also had some smaller, fuzzy, primitive body feathers that we associate with dinosaurs,” said O’Connor.
She and her coauthors hypothesize that the hesperornithiforms’ feathers weren’t as effective as the more complex Neornithes feathers in insulating bird bodies from the extreme temperatures after the asteroid strike—which could explain why the diving birds perished in the inhospitable End-Cretaceous conditions, while the ancestors of modern birds found new life in their superior feathers. 
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Lead Image: Andrey Atuchin
