When you picture a dinosaur, what does it look like? For Jingmai O'Connor, paleobiologist and associate curator of reptiles at the Field Museum of Chicago, the dinosaurs she studies look a lot more like birds."If you looked at an artist's reconstruction of something like Velociraptor or Microraptor ... you would see that it pretty much looks the same as a bird," Jingmai says. "In terms of the plumage, the soft tissues covering the body, it would have looked very, very birdlike."In this episode, Short Wave delves into the dinosaur-avian connection. Which dinosaurs had feathers? Were they using them to fly? And once and for all – what are those ancient dinosaurs' relationship to birds today? Have other dinosaur questions you want us to unravel? Email us at [email protected] — we'd love to hear from you!Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What do we typically picture when we think of dinosaurs?
You're listening to Shortwave from NPR. Hey short wavers, Regina Barber here. I'm going to start today's episode with a question. When I say dinosaur, what do you picture in your head? Maybe a stegosaurus, like a chunky guy with diamond-shaped plates and a ridge along its back. Or a triceratops with like huge horns, kind of like a rhinoceros, but like a little kid had drawn it.
Or a T-Rex, classic, big body, big teeth, tiny little arms. But what you might not think of are feathers. It turns out many dinosaurs did have feathers. We found that out in the mid-90s when dinosaur fossils were discovered at the bottom of a lake in China.
In lakes, you have no scavengers and you have guaranteed burial. And so this leads to really exceptional preservation. And these fossils from China, the most common soft tissue they preserve are feathers.
This is Jingmei O'Connor. She's a dinosaur paleobiologist and the associate curator of fossil reptiles at the Field Museum of Chicago. And she says that the structure of a feather is mostly keratin, which is a protein that usually breaks down over time.
But when feathers have pigment inside them, they have these pigment-bearing mono-organelles called melanosomes. They're in our eyes, they're in the ink sacs of squid, they're everywhere, right? So these organelles are extremely decay-resistant. So the keratin matrix of the feather is gone, but these pigment-containing mono-organelles get fossilized very easily.
And that's why we can now tell you, sort of, what color some feathered dinosaurs were by looking at these melanosomes.
For the longest time, I admit, I thought the people at the museums or in the movies were like, taking some creative license. Like, how would they know that all of these dinosaurs had those specific colors, that stripe pattern, these feathers? Because the thing that always threw me off was that some dinosaur displays in the museums had feathers and others didn't have any. Like, what gives?
But of course, they were as accurate as possible. The colors, the patterns, and even which dinosaurs had feathers. Because spoiler alert, not all of them did. So today on the show, the gorgeous, vivid world of dinosaur feathers. Which dinosaurs had feathers? Were they using them to fly? And once and for all, what are ancient dinosaurs' relationship to birds today?
You're listening to Shortwave, the science podcast from NPR.
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Chapter 2: Did all dinosaurs have feathers?
Okay, Jingmei, I'm really excited to talk to you about dinosaurs and flight and all of that. And I think we need to start with the basics. Feathers, did all dinosaurs have them? How do we know?
So it's very likely that only smaller dinosaurs were feathered and theropods in particular. So basically, we know that the earliest dinosaur was a small, warm-blooded animal. And the earliest feathers evolved for the same reason as fur in mammals, in order to help with thermoregulation in a warm-blooded animal, right?
If you are small and you're warm-blooded and you don't have something to keep your body heat in, you're just shedding the body heat off your skin, it would take a ton of energy to maintain a high body temperature. So you need insulation.
Okay, so then if dinosaurs got like bigger, they probably wouldn't need as much insulation. I'm guessing like cold-blooded ones wouldn't either.
Is that right? So not all dinosaurs would have been feathered. And also when we talk about feathers and dinosaurs, we're talking about these early evolutionary stages and feathers. When we think about a feather in the modern sense, that is restricted to a very narrow group of theropod dinosaurs. In fact, only three... Non-bird groups of dinosaurs had those types of feathers.
So it's a little bit semantics. When you say feather, do you mean even the earliest evolutionary stage of a feather all the way up to the very complex feathers we see today? Or do we restrict that term? That's why sometimes we'll call those primitive feathers proto-feathers. And then we'll refer to the modern, very complex feather as a panaceous feather.
You were discussing about like why these protofeathers don't look anything like modern feathers. Can you get into that? Like what did they look like then?
Protofeathers basically just look like hair. They're very simple monofilamentous structures, right?
Got it.
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Chapter 3: What are the different types of feathers in dinosaurs?
Like feathers and hair, one of them starts by kind of folding inwards in the skin and then forming the follicle. And the other forms first as a projection out of the dermis and then becomes this complex structure. Yeah. Also feathers are the only keratinous structures that don't grow continuously throughout life.
When that actually evolved, we're not sure because modern feathers are so complex that they can't keep growing, right? They have very distinct distal end and proximal end that are morphologically, like the shape of them is very different. Whereas a hair or a beak or fingernails are all just the same, so they can just continuously grow.
Okay, so this brings me to a question I've been dying to ask. Are birds descendants of dinosaurs or are they actually dinosaurs?
Birds are dinosaurs.
Okay.
Birds are one group of dinosaurs. And I think when we think of a dinosaur, we think of Triceratops or Stegosaurus. And these are dinosaurs that are not closely related to birds. Like, for example, if you looked at an artist's reconstruction of something like Velociraptor or Microraptor, a small feathered theropod dinosaur, very closely related to birds.
you would see that it pretty much looks the same as a bird. I mean, there's some structural, like, you know, differences in proportions and some, you know, minor differences in the skeleton. But in terms of the plumage, like the soft tissues covering the body, it would have looked very, very bird-like.
Okay, but let's talk about birds then. What made them so well-equipped for the modern world in a way that, like, these other dinosaurs, they were not equipped? How did these dinosaurs that were basically birds survive?
Probably the million dollar question in my area of dinosaur paleobiology is, you know, understanding the selectivity of the end Cretaceous mass extinction. Why did only birds survive? And it's not just that birds survived. There were lots of birds that go extinct alongside non-avian dinosaurs. It's really just one group of birds that survives. So why did they make it through and nobody else?
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Chapter 4: Are modern birds actually descendants of dinosaurs?
Chapter 5: How do feather colors in dinosaurs get preserved?
And that's why we can now tell you, sort of, what color some feathered dinosaurs were by looking at these melanosomes.
For the longest time, I admit, I thought the people at the museums or in the movies were like, taking some creative license. Like, how would they know that all of these dinosaurs had those specific colors, that stripe pattern, these feathers? Because the thing that always threw me off was that some dinosaur displays in the museums had feathers and others didn't have any. Like, what gives?
But of course, they were as accurate as possible. The colors, the patterns, and even which dinosaurs had feathers. Because spoiler alert, not all of them did. So today on the show, the gorgeous, vivid world of dinosaur feathers. Which dinosaurs had feathers? Were they using them to fly? And once and for all, what are ancient dinosaurs' relationship to birds today?
You're listening to Shortwave, the science podcast from NPR.
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Okay, Jingmei, I'm really excited to talk to you about dinosaurs and flight and all of that. And I think we need to start with the basics. Feathers, did all dinosaurs have them? How do we know?
So it's very likely that only smaller dinosaurs were feathered and theropods in particular. So basically, we know that the earliest dinosaur was a small, warm-blooded animal. And the earliest feathers evolved for the same reason as fur in mammals, in order to help with thermoregulation in a warm-blooded animal, right?
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Chapter 6: What does the structure of a feather tell us about dinosaurs?
If you are small and you're warm-blooded and you don't have something to keep your body heat in, you're just shedding the body heat off your skin, it would take a ton of energy to maintain a high body temperature. So you need insulation.
Okay, so then if dinosaurs got like bigger, they probably wouldn't need as much insulation. I'm guessing like cold-blooded ones wouldn't either.
Is that right? So not all dinosaurs would have been feathered. And also when we talk about feathers and dinosaurs, we're talking about these early evolutionary stages and feathers. When we think about a feather in the modern sense, that is restricted to a very narrow group of theropod dinosaurs. In fact, only three... Non-bird groups of dinosaurs had those types of feathers.
So it's a little bit semantics. When you say feather, do you mean even the earliest evolutionary stage of a feather all the way up to the very complex feathers we see today? Or do we restrict that term? That's why sometimes we'll call those primitive feathers proto-feathers. And then we'll refer to the modern, very complex feather as a panaceous feather.
You were discussing about like why these protofeathers don't look anything like modern feathers. Can you get into that? Like what did they look like then?
Protofeathers basically just look like hair. They're very simple monofilamentous structures, right?
Got it.
Developmentally, totally different than hair. But superficially, that's what they look like. And superficially, they probably both evolve for a similar purpose. Got it. Why are they so different? So basically the difference between a feather, a proto feather, which looks like a hair and hair is in their development.
Like feathers and hair, one of them starts by kind of folding inwards in the skin and then forming the follicle. And the other forms first as a projection out of the dermis and then becomes this complex structure. Yeah. Also feathers are the only keratinous structures that don't grow continuously throughout life.
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