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Now a story about a fossil smaller than a golf ball. NPR's Ari Daniel reports it may help explain why some birds died out with the dinosaurs while others survived to give rise to the birds we know today.
ARI DANIEL, BYLINE: Paleontology can be quite physical. In 2016, David DeMar, the lab manager at the Burke Museum in Seattle, was doing fieldwork in the rocky badlands of Montana.
DAVID DEMAR: We all get down on our hands and knees, and I start crawling up the hill. And I notice this little dark round object on the ground.
DANIEL: So he picked up the cherry-sized fossil.
DEMAR: And I start looking at the surface of it, and then I roll it over. And I was like, you got to be kidding me.
DANIEL: Embedded in a small crack on the surface was a tiny fossilized branching structure. DeMar quickly radioed his colleagues.
DEMAR: Told them that, hey, I think I found a bird feather.
DANIEL: Subsequent analysis confirmed it. Not only was this the first fossilized feather from this part of the world, says Jingmai O'Connor, an associate curator at the Field Museum of Natural History in Chicago...
JINGMAI O'CONNOR: It is, without a doubt, the best feather we've ever found from the age of dinosaurs.
DANIEL: It's from the end of that age, some 66 million years ago, right before a giant asteroid slammed into the Earth. When O'Connor joined the project, very little was known about the feather.
O'CONNOR: My goal was to try to figure out what animal this feather belonged to and then - what can this exceptional feather tell us?
DANIEL: The round nodule the feather was sitting in turned out to be something called a coprolite. It's a chunk of fossilized feces likely produced, says O'Connor, by a large meat-eating dinosaur.
O'CONNOR: So I would argue that Tyrannosaurus rex or Nanotyrannus are the more likely candidates.
DANIEL: The team CT-scanned the coprolite and found it contained other feathers, a couple bone pieces and two tiny fish scales. O'Connor says the feathers and bones may have come from the same animal, probably an ancient aquatic swimming bird.
O'CONNOR: Kind of like a loon or a grebe. They're foot-propelled divers.
DANIEL: The fish scales may have been part of the ancient bird's last supper before it, too, became a meal for an animal like a T. rex. That predator later defecated all these specimens out into one precious package. Now, this bird was one of many types that went extinct alongside the dinosaurs.
O'CONNOR: Only one group of birds survives when the asteroid impact happens.
DANIEL: The group that gave rise to modern birds. A big question is what allowed them to make it through the ensuing drop in global temperature. Perhaps, O'Connor speculates, they were better insulated, because she noticed that some of the fossilized body feathers inside the coprolite from the ancient bird that ultimately died out appeared to lack the insulation of their modern counterparts.
O'CONNOR: I'm not saying this is the reason. I'm saying it's a contributing factor to the extinction.
DANIEL: The research is published in the journal Current Biology. Julia Clarke is an evolutionary biologist at UT Austin who wasn't involved in the study.
JULIA CLARKE: I think it's a stretch to explain the survivorship of some and the extinction of others from that evidence.
DANIEL: Still, she's taken by the snapshot of a food web apparently captured inside a piece of poo.
CLARKE: A dinosaur ate an aquatic bird that ate a fish, almost like they've discovered a Cretaceous turducken.
DANIEL: What Jingmai O'Connor says they've discovered is a new way of accessing crucial specimens - coprolites.
O'CONNOR: We now have this whole potential to find fossilized, not just feathers, but fur and other soft-tissue structures.
DANIEL: She says it's worthwhile work. Understanding past extinctions tells us about the current extinction crisis and who may survive and who may not.
Ari Daniel, NPR News.
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