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It's Okay to Be Smart: How Did Giant Pterosaurs Fly?

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      Hey, smart people, Joe here. So my friend Emily Graslie from "The Brain Scoop" came to visit a while back, and we did what you do when you're hanging out with Emily, which is go look at some bones from some awesome prehistoric creatures. That big thing above our heads, that's a giant pterosaur named Quetzalcoatlus. Now, seeing his bones up close kind of blew my mind. I mean, this was a giant winged reptile that stood as tall as a giraffe, probably weighed as much as a grizzly bear, which would make it the largest and heaviest animal that's ever flown. To put that into perspective, this is a wandering albatross, the largest flying animal alive today. And this is Argentavis, an extinct bird of prey and the largest flying bird that ever lived. And that is Quetzalcoatlus. It's closer in size to an F-16 than a bird. Now, I don't know about you, but it's pretty hard for me to imagine a creature that huge taking to the skies. I mean, you can't argue with the laws of physics. And just because something has wings doesn't mean it can fly.

      (Describer) ...like a penguin.

      [bird trills]

      Now it turns out scientists have been trying to solve this mystery of whether giant pterosaurs could fly for decades, and that they might have finally done it by thinking not just like paleontologists, but also by looking to aerospace engineering and mathematics.

      [music playing]

      (Describer) Title: It's Okay To Be Smart A man wears headphones on a video call.

      Dr. Michael Habib is one of those scientists. So I called him up to get some answers. I am a paleontologist. We're called biomechanists, which is to say that I study the motion and physics of living and fossil animals. Can you just give us an idea, what is a pterosaur? Pterosaurs represent an extinct group of flying reptiles. They can be found in small toys marked "dinosaurs," which is terribly misleading because they were not, in fact, dinosaurs. There are such a thing as flying dinosaurs. We call them birds. And there are about 12,000 living species of them. But the last pterosaurs perished at the end of the Cretaceous, along with the last of the non-bird dinosaurs.

      (Joe Hanson) These guys were, by far, the earliest flying vertebrates. I mean, the earliest pterosaur fossils go back to about 230 million years ago, and they owned the skies for almost 160 million years. Birds have only existed for about 150 million years, so that's pretty impressive. But pterosaurs are not dinosaurs. I just want to emphasize that again. Not dinosaurs. They're their own thing. The Dinobots have some explaining to do.

      (Describer) A cartoon mechanized Pterosaur flies.

      [music playing]

      Where were we? Where the average pterosaur was around, say, one to two meters wingspans, the smallest one could fit in the palm of your hand. Sounds cute. And--which is very cute. And when I'm talking about the largest pterosaurs, I'm talking about a three-way tie between Quetzalcoatlus, which was the first giant discovered. More recently, discovered one called Hatzegopteryx of Transylvania. And then just recently named is Cryodrakon, the frozen dragon, which is from Alberta, Canada. OK, Cryodrakon is hands down the coolest name ever given to any extinct reptile. I mean, frozen dragon. Eat your heart out, George R.R. Martin. Based on what we see alive on earth today, it is pretty hard to imagine one of these giants actually flying. So how could they have done it? Well, it turns out to fly, you really need to master two things-- being able to generate lift to stay in the air and also getting into the air in the first place. Now, staying in the air is actually not the hardest part for a giant flying creature. The wings of birds and bats and pterosaurs are shaped like airfoils. They're thick at one end, where the bones of the limb are and thinner at the trailing end, where it's either feathers or the wing membrane. The flapping draws this airfoil through the air, creating both lift and thrust. And it turns out, a big animal with big flapping muscles like Quetzalcoatlus would have had more than enough power to create sufficient lift and thrust to fly.

      (Describer) He holds an origami version.

      Hmm, hmm, hmm. You know, to show you what I mean, I think we should take a closer look at some bones. Some old bones. Luckily, Quetzalcoatlus was discovered in my home state of Texas, and those bones happen to be just down the road at the University of Texas Vertebrate Paleontology Library. So these are the actual bones of Quetzalcoatlus.

      (Describer) Matthew Brown:

      This really heavy drawer is full of some of the wing bones from this giant flying pterosaur. There are a lot of adaptations throughout the skeleton of a pterosaur that allow it to fly. And one of the things that really jumps out at people when they look at this big humerus, so there's this big prong that sticks up here out of the bone that is the source for all of the muscles to attach and stretch across to the chest, where they attach to the breastbone, basically. So the bones tell us that these things had massive arm and chest muscles in order to provide enough force to cut that giant airfoil wing through the air. But that's not the only flight adaptation that we can see in pterosaur bones. I know one of the things that birds' adaptation is they have partially hollow bones? That's right, yeah.

      (Describer) Brown:

      And so pterosaurs do the same thing. So we can take a look at the smaller species to compare the cross section of a broken bone.

      Let's do it. [grunts]

      (Describer) Joe helps Brown close the drawer and mouths, "been working out". In the next drawer...

      [whispering] I'm working out.

      So this is the ulna from the small animal. So if we look at this in cross section, you can see that there's a thin rim of dark gray bone around the outside of this. It's about, oh, two millimeters or so wide.

      (Joe Hanson) All that lighter part in the middle would have been hollow when this pterosaur was alive, just like bird bones. But that bone is not much thicker than a large egg shell, and it had to support the weight of all of those muscles and a grizzly bear-sized body in flight without snapping in half. I mean, how did it do that? So if you're a pterosaur, you have probably the weirdest hands that have ever evolved.

      (Describer) Habib:

      They only had four fingers. They did not have a fifth finger, so your pinky finger would be absent. And digits 1, 2, and 3, so your thumb, index finger, and middle finger, would be basically normal for a reptile. And then the fourth finger would be enormous. The fourth finger, your ring finger, would be about as big around as your wrist and as long as your entire leg. That's tough to even imagine that. I'm sitting here looking at my own hand going, OK, the first part makes sense. But then you lost me with the ring finger. Just imagine how much our rings would've cost. I know. Gosh. The weight support for the animal is basically hanging, in large part, off this finger, which is crazy. So their wing bones, including their ring finger, is hollow. So they have a really large diameter, which makes it surprisingly strong. OK, so that's how giant pterosaurs were adapted to staying in the air. But remember, there's a second thing an animal has to master in order to fly-- actually getting up in the air. They need to give themselves enough of a speed boost so that the combination of forward speed from takeoff and the flapping speed from the wings creates enough lift, and that turns out to be the hard part for giant flyers. Now, when I was a kid, the first time I ever saw a pterosaur was in the Disney movie "Fantasia." So I grew up thinking that pterosaurs lived on cliffs and basically jumped off the edge to start flying. Well, my childhood is a lie. It does not actually help to drop off of a cliff to get that speed.

      (Describer)

      You're accelerating one gravity down at that point, and you really want to be accelerating a couple of gravities up. And the way that an animal, say, on the ground, flying animal, gets going up and forward quickly is to jump. OK, I have a confession. I've gone my entire life thinking birds launch themselves into flight by just flapping their wings and lifting themselves into the air. But if you watch a bird in slow motion, it turns out that they start with their wings up and jump into flight.

      (Michael Habib) It all happens so fast, by our standards, that it looks like they're wing launching, but they're not. They're leg launching. So about 80% to 90% of the power for takeoff, in most birds, comes from the legs. It turns out that most flight animals are actually quite good jumpers, and that's not coincidental. That's because they need that in order to take off. But pterosaurs aren't birds. In fact, when it comes to taking off, they have an advantage that birds don't have, and it goes back to those really weird wings.

      (Michael Habib) We know that they walk on folded wings, so they're walking on their hands and their feet. And they probably were very good jumpers for their size. A giraffe can't jump very high. It's actually quite heavy. It's got a very big torso. A pterosaur might be that height, but it would be a fraction of the weight, and it would actually have more muscle in its limbs. These things should be able to jump a couple of meters. That is more than enough to give them the clearance and speed that they need to get flapping. Unfortunately, we don't know exactly what it would've looked like to see a big giraffe bear dragon jump several meters into the sky, but we can get an idea thanks to another flying animal. Bats that take off from the ground walk on their wings, folded wings, and on their feet. So they're walking what we call quadrupedally, on all four limbs, which means all four of them are also available for jumping. So when they jump, they get a little bit of force off the hind limbs, and then they get most of the force off the forelimbs because the wings are bigger than the legs, of course, because they're a flying animal. And they can really take off like a rocket. So birds, they're also tetrapods. They also got four limbs. But they basically said, two of you are only going to be used for this one special thing. And it sounds like pterosaurs were like, we're going to combo our arms. We're going to get two good things out of these-- both leaping and flying. Yeah, they're taking the combo approach, which ends up giving you a lot more room for getting big, because birds end up getting stuck. You've got one motor that's specialized for, OK, you're going to be for swimming and running and jumping and taking off. And the other one is, OK, once we get up, then you're going to take over and do the flapping and keep us up. And this is the key thing that has kept birds from getting to be giraffe size. If you make your flapping muscles bigger, then that's more payload you have to push up with your launching muscles, so then they have to be bigger. But if you make the launching muscles bigger, then that's more payload you have to carry in the air with your flapping muscles. So at some point, you're either too heavy to launch or too heavy to keep in the air. But if you use the same motor for your flapping and your take-off, then you can be way heavier before physics keeps you on the ground. That also explains very nicely why a lot of the largest pterosaurs have enormous forelimbs and actually really shockingly small hind limbs. One of my favorites is called Anhanguera. That's a thing from Brazil. And this animal has about a four- to five-meter wingspan. It's like 15 feet tip-to-tip in the air. Has a head that is well over a meter long. It's like a meter-and-a-half. The neck is not too far off from that. The body has got a big chest, but then the rest of the body is like an afterthought. It's like a tiny thing. And the hind limbs are so small that the feet, both feet, will fit in one eye socket. Wow. I mean, I don't want to laugh at pterosaurs, but they do have really goofy body ratios, so much head and so much neck. And the farther you go back, you're right, it's just like somebody ran out of energy and sort of like, I'll finish this later. My joke is that they skipped legs day. Yeah, they definitely skipped leg day. So that's how we think the largest flying animal ever took to the skies. What I love about this is that scientists wouldn't have solved this mystery if they hadn't combined different kinds of science together, not just paleontology, but aerospace engineering and mechanics and computer modeling too. It used to be that we'd have to sit down with the fossils or casts of the fossils to try to reconstruct them and figure out how those animals moved. And what we've done a lot of lately

      (Describer) Brown:

      is CT scanning or laser surface scanning of the bones, and we can study those quantitatively, making computer models to try to reconstruct and test the different ways that these animals might have moved around in their lifetime. So you build that pterosaur inside of the computer. Yeah. Put it in a wind tunnel, throw it off a cliff. That's right, yeah. Put it in an attack dive, all kinds of cool stuff. Yeah. We've had people who work on designing gliders and other aircraft come in and look at, because when they're trying to find efficiencies and make faster airplanes and more fuel efficient airplanes, looking at the fossil record, is this something that we can apply? Because we've only been working on flight for, I don't know, a century and a half or something... We haven't been at it very long. ...and they had tens of millions of years of practice. But as incredibly adapted as pterosaurs were to flying, they were no match for a rock the size of a small city falling out of the sky and setting the whole atmosphere on fire. So unlike birds, all that we know of pterosaurs is from their bones. And honestly, after seeing those bones up close, I can't decide if it would be really cool or completely terrifying to have pterosaurs around today.

      (Describer) Habib:

      I think it would depend on which ones, right? I think I would be perfectly happy seeing a little fits-in-the-palm-of-my-hand-size pterosaur perched on my porch. But that would be like, oh, there's a Quetzalcoatlus circling. I'm sorry, we can't go outside today because it might eat the kids. That would be-- Hey, it's like in "Game of Thrones." The dragons were cute when they were babies, but later on they became real problem children. I'm kind of glad that we got chickens instead. Stay curious.

      (Describer) Title: PBS

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      Now Playing As: English with English captions (change)

      The largest pterosaurs like Quetzalcoatlus were closer in size to airplanes than birds. No flying animal alive today comes close to their huge size. Part of the "It's Okay to Be Smart" series.

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