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. Seeing that up close kinda blew my mind. I
mean this was a giant winged reptile that stood as tall as a giraffe and 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. It turns out scientists have been trying to
solve this mystery of whether giant pterosaurs could fly for decades. And they might have
finally done it, by thinking not just like paleontologists, but also by looking to aerospace
engineering and mathematics. [MUSIC] Michael Habib is one of those scientists,
so I called him up to get some answers. I am a paleontologist, what we call a biomechanist,
which is to say I study the motion and physics of living and fossil animals. Can you give us an idea of, what is a pterosaur So, 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 12,000 living species of them. But the last pterosaurs perished
at the end of the Cretaceous with the last of the non-bird dinosaurs. These guys were by far the earliest flying
vertebrates. 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. Where were we? The average pterosaur was around, say, one
to two meters wingspan. The smallest one could fit in the palm of your hand Sounds cute! Which is very cute. And when you’re talking
about the largest pterosaurs I’m talking about a three-way tie between Quetzalcoatlus,
which is the first giant discovered. More recently rediscovered one called Hatzegopteryx
from Transylvania, and then just recently named is Cryodrakon “The frozen dragon,”
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’s 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, bats, and pterosaurs are
shaped like airfoils, 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. Turns out a big animal with big
flapping muscles, like Quetzalcoatlus, would have more than enough power to create sufficient
lift and thrust to fly. 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. Yeah, so these are the actual bones of Quetzalcoatlus. Wow And this really heavy drawer is full of some
of the wing bones from this giant flying pterosaur. So there are a lot of adaptations throughout
the skeleton of the pterosaur that allowed it to fly. And one of the things that jumped
out when people look at this humerus is there’s this big prong that sticks up here, out of
the bone that is the source for all the muscles to attach and stretch across the chest where
they attach to the breast bone basically. So the bones tell us 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 we can see in pterosaur
bones. I know one of the things that birds did, an
adaptation, is they have partially hollow bones? Yeah that’s right, and pterosaurs did the
same thing. So we can take a look at the smaller species to compare the cross section of broken
bones. Ugghhh (I work out) So this is the ulna from the small animal.
So if we look at this in cross section, you can see there is a thin rim of dark gray bone
about 2 mm wide. All that lighter part in the middle would
have been hollow when this pterosaur was alive, just like bird bones. But that bone’s not much thicker than a
large egg shell. And it had to support the weight of all those muscles, and a grizzly
bear-sized body in flight, without snapping in half. How did it do that? So, if you’re a pterosaur, you have the
weirdest hands that ever evolved. They only had four fingers, they did not have a fifth
finger, so your pinky finger would be absent. And your thumb, middle, and index finger would
be basically normal for a reptile. And then the fourth finger, your ring finger would
be enormous. It would be as thick as your wrist and as long as your entire leg. It’s … that’s tough to even imagine.
I’m sitting here looking at my own hand thinking, ok that first part makes sense.
But you lost me with the ring finger. Imagine how much rings would cost! J: I know! The weight support for this animal is essentially
hanging off this finger. Which is crazy. All of their wing bones, including that ring finger,
are hollow. But it has that 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 the 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 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 a cliff
to get that speed. 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, it’s going up and forward quickly, is to jump. I have a confession: I’ve gone my entire
life thinking birds launched themselves into the air by just flapping their wings and lifting
themselves into the air. But if you watch a bird in slow motion, it turns out they start
with their wings up, and jump into flight. H: 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 80-90% of the power for takeoff in most birds comes from the legs. It turns out
most flying animals are good jumpers, and that’s not coincidental. It’s because
they need that 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. We know that they walked on folded wings.
And they were probably good jumpers for their size. A giraffe can't jump very high, it’s
actually quite heavy, it has a big torso. A pterosaur might be that height, but it’s
a fraction of the weight. And it would have more muscle in its limbs. These things should
be able to jump a couple of meters. That is more than they need to get the clearance and
speed they need to start flapping. Unfortunately, we don’t know exactly what
it would have 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 and their feet. So they’re walking quadrupedally, on all four limbs. Which means
that all four are available for jumping. So when they jump, they get a little bit of force
off the hindlimbs, and they get most of the force from the forelimbs, because the wings
are bigger than the legs, it's a flying animal. And they can REALLY take off like a rocket. Birds - they’re also tetrapods, they have
four limbs, but they basically said “two of you are only going to be used for this
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 this. We’re going to get leaping and flying.” Yeah, they’re taking the combo approach.
It ends up giving a lot more room for getting big. Because birds end up getting stuck. You’ve
got one motor that’s specialized for swimming, running, and jumping, and taking off. And
the other one is okay, once we get up, you’re going to take over and do the flapping and
to keep us up. And this is the key thing that has kept birds
from getting to be giraffe-sized. If you make your flapping muscles bigger, that’s more
payload you have to push up with your launching muscles, so they have to be bigger. But if
you make the launching muscles bigger that’s more payload you have to carry in the air
with your flapping muscles. 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 takeoff
then you can be way heavier before physics keeps you on the ground. That also explains, rather nicely, why the
largest pterosaurs have enormous forelimbs but shockingly small hindlimbs. One of my favorites, called Anhanguera, from
Brazil, this animal has a 4 to 5 meter wingspan, a head that is well over a meter long, the
neck is not too far off from that. The body - it has a big chest but the rest of the body
is like an afterthought, it’s a tiny thing. And the hindlimbs are so small that 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 like somebody ran out of energy and was like, I’ll finish
this later. Yeah, my joke is always that they skip leg
day. 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 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. So it would used to be that we’d have to
sit down with the fossils or casts of the fossils because the bones are too delicate
to try and figure out how these animals moved, and what we’ve done a lot of lately is CT
scanning or laser surface scanning of the bones, and we can study those quantitatively,
making computer models so we can test how these animals might have moved around in their
lifetime. You build that pterosaur inside the computer,
put it in a wind tunnel, throw it off of a cliff, put it in an attack dive, all kinds
of cool stuff. We’ve had people who work on designing gliders
and other aircraft come in and look because when they’re trying to find efficiencies
and make faster planes and more fuel efficient planes, looking at the fossil record is something
we can apply. We’ve only been working on flight for like
a century and a half… Yeah, we haven’t been working 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 the sky and
setting the atmosphere on fire. So unlike birds, all 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. I think it would depend on which ones. I think
i would be perfectly happy seeing a little fit-in-the-palm-of-my-hand pterosaur perched
on my porch, but, Quetzalcoatlus is circling, we can’t go outside today because it might
eat the kids… that would be… 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 kinda glad we got chickens instead. Stay curious.
I wonder why bats never got big.