How Did Giant Pterosaurs Fly?

published on July 9, 2020

Hey smart people, Joe hereSo my friend Emily Graslie from The BrainScoop came to visit a while back, and we didwhat you do when you’re hanging out withEmily, which is go look at some bones fromsome awesome prehistoric creaturesThat big thing above our heads? That's a giantpterosaur named QuetzalcoatlusSeeing that up close kinda blew my mind Imean this was a giant winged reptile thatstood as tall as a giraffe and probably weighedas much as a grizzly bear, which would make

It the largest and heaviest animal that’sever flownTo put that into perspective, this is a wanderingalbatross, the largest flying animal alivetoday And this is Argentavis, an extinctbird of prey and the largest flying bird thatever lived And that is Quetzalcoatlus It’scloser in size to an F-16 than a birdNow, I don’t know about you, but it’spretty hard for me to imagine a creature thathuge taking to the skies I mean, you can’targue with the laws of physics, and just because

Something has wings, doesn’t mean it canflyIt turns out scientists have been trying tosolve this mystery of whether giant pterosaurscould fly for decades And they might havefinally done it, by thinking not just likepaleontologists, but also by looking to aerospaceengineering and mathematicsMichael Habib is one of those scientists,so I called him up to get some answersI am a paleontologist, what we call a biomechanist,which is to say I study the motion and physics

Of living and fossil animalsCan you give us an idea of, what is a pterosaurSo, pterosaurs represent an extinct groupof flying reptiles They can be found in smalltoys marked “dinosaurs” which is terriblymisleading because they were not in fact dinosaursThere are such a thing as flying dinosaurs,we call them birds and there are 12,000 livingspecies of them But the last pterosaurs perishedat the end of the Cretaceous with the last

Of the non-bird dinosaursThese guys were by far the earliest flyingvertebrates The earliest pterosaur fossilsgo back to about 230 million years ago, andthey owned the skies for almost 160 millionyears Birds have only existed for about 150million years, so that’s pretty impressiveBut pterosaurs are not dinosaurs I just wantto emphasize that again Not dinosaurs They’retheir own thing The Dinobots have some explainingto do

Where were we?The average pterosaur was around, say, oneto two meters wingspan The smallest one couldfit in the palm of your handSounds cute!Which is very cute And when you’re talkingabout the largest pterosaurs I’m talkingabout a three-way tie between Quetzalcoatlus,which is the first giant discovered More

Recently rediscovered one called Hatzegopteryxfrom Transylvania, and then just recentlynamed is Cryodrakon “The frozen dragon,”from Alberta, CanadaOk, Cryodrakon is hands down the coolest nameever given to any extinct reptile I mean“frozen dragon”! Eat your heart out GeorgeR R MartinBased on what we see alive on Earth today,it’s pretty hard to imagine one of thesegiants actually flying So, how could theyhave done it? Well, it turns out, to fly,

You really need to master two things: beingable to generate lift to stay in the air,and also, getting into the air in the firstplaceNow, staying in the air is actually not thehardest part for a giant flying creatureThe wings of birds, bats, and pterosaurs areshaped like airfoils, thick at one end, wherethe bones of the limb are, and thinner atthe trailing end where it’s either feathersor the wing membrane The flapping draws thisairfoil through the air, creating both lift

And thrust Turns out a big animal with bigflapping muscles, like Quetzalcoatlus, wouldhave more than enough power to create sufficientlift and thrust to flyYou know, to show you what I mean, I thinkwe should take a closer look at some bonesSome old bones Luckily, Quetzalcoatlus wasdiscovered in my home state of Texas and thosebones happen to be just down the road at theUniversity of Texas Vertebrate PaleontologyLibrary

Yeah, so these are the actual bones of QuetzalcoatlusWowAnd this really heavy drawer is full of someof the wing bones from this giant flying pterosaurSo there are a lot of adaptations throughoutthe skeleton of the pterosaur that allowedit to fly And one of the things that jumpedout when people look at this humerus is there’sthis big prong that sticks up here, out ofthe bone that is the source for all the muscles

To attach and stretch across the chest wherethey attach to the breast bone basicallySo the bones tell us these things had massivearm and chest muscles in order to provideenough force to cut that giant airfoil wingthrough the air But that’s not the onlyflight adaptation we can see in pterosaurbonesI know one of the things that birds did, anadaptation, is they have partially hollowbones?

Yeah that’s right, and pterosaurs did thesame thing So we can take a look at the smallerspecies to compare the cross section of brokenbonesUgghhh (I work out)So this is the ulna from the small animalSo if we look at this in cross section, youcan see there is a thin rim of dark gray boneabout 2 mm wideAll that lighter part in the middle wouldhave been hollow when this pterosaur was alive,

Just like bird bonesBut that bone’s not much thicker than alarge egg shell And it had to support theweight of all those muscles, and a grizzlybear-sized body in flight, without snappingin half How did it do that?So, if you’re a pterosaur, you have theweirdest hands that ever evolved They onlyhad four fingers, they did not have a fifthfinger, so your pinky finger would be absent

And your thumb, middle, and index finger wouldbe basically normal for a reptile And thenthe fourth finger, your ring finger wouldbe enormous It would be as thick as yourwrist and as long as your entire legIt’s … that’s tough to even imagineI’m sitting here looking at my own handthinking, ok that first part makes senseBut you lost me with the ring fingerImagine how much rings would cost!

J: I know!The weight support for this animal is essentiallyhanging off this finger Which is crazy Allof their wing bones, including that ring finger,are hollow But it has that large diameterwhich makes it surprisingly strongOk, so that’s how giant pterosaurs wereadapted to staying in the air, but remember,there’s a second thing an animal has tomaster in order to fly: Actually getting up

In the air They need to give themselves enoughof a speed boost so that the combination ofthe forward speed from takeoff and the flappingspeed from the wings creates enough liftAnd that turns out to be the hard part forgiant flyersNow, when I was a kid, the first time I eversaw a pterosaur was in the Disney movie FantasiaSo I grew up thinking pterosaurs lived oncliffs and basically jumped off the edge tostart flying Well… my childhood is a lie

It does not actually help to drop off a cliffto get that speed You’re accelerating onegravity down at that point, and you reallywant to be accelerating a couple of gravitiesup And the way that an animal, say on theground, it’s going up and forward quickly,is to jumpI have a confession: I’ve gone my entirelife thinking birds launched themselves intothe air by just flapping their wings and liftingthemselves into the air But if you watch

A bird in slow motion, it turns out they startwith their wings up, and jump into flightH: It all happens so fast by our standardsthat it looks like they’re wing launching,but they’re not They’re leg launching,so about 80-90% of the power for takeoff inmost birds comes from the legs It turns outmost flying animals are good jumpers, andthat’s not coincidental It’s becausethey need that to take offBut pterosaurs aren’t birds In fact, whenit comes to taking off, they have an advantage

That birds don’t have And it goes backto those really weird wingsWe know that they walked on folded wingsAnd they were probably good jumpers for theirsize A giraffe can't jump very high, it’sactually quite heavy, it has a big torsoA pterosaur might be that height, but it’sa fraction of the weight And it would havemore muscle in its limbs These things shouldbe able to jump a couple of meters That ismore than they need to get the clearance andspeed they need to start flapping

Unfortunately, we don’t know exactly whatit would have looked like to see a big giraffe/bear/dragonjump several meters into the sky, but we canget an idea thanks to another flying animalBats that take off from the ground, walk ontheir wings and their feet So they’re walkingquadrupedally, on all four limbs Which meansthat all four are available for jumping Sowhen they jump, they get a little bit of forceoff the hindlimbs, and they get most of theforce from the forelimbs, because the wingsare bigger than the legs, it's a flying animal

And they can REALLY take off like a rocketBirds – they’re also tetrapods, they havefour limbs, but they basically said “twoof you are only going to be used for thisspecial thing” And it sounds like pterosaurswere like, “we’re going to combo our arms,we’re going to get two good things out ofthis We’re going to get leaping and flying”Yeah, they’re taking the combo approachIt ends up giving a lot more room for getting

Big Because birds end up getting stuck You’vegot one motor that’s specialized for swimming,running, and jumping, and taking off Andthe other one is okay, once we get up, you’regoing to take over and do the flapping andto keep us upAnd this is the key thing that has kept birdsfrom getting to be giraffe-sized If you makeyour flapping muscles bigger, that’s morepayload you have to push up with your launchingmuscles, so they have to be bigger But ifyou make the launching muscles bigger that’s

More payload you have to carry in the airwith your flapping muscles At some pointyou’re either too heavy to launch or tooheavy to keep in the air But if you use thesame motor for your flapping and your takeoffthen you can be way heavier before physicskeeps you on the groundThat also explains, rather nicely, why thelargest pterosaurs have enormous forelimbsbut shockingly small hindlimbs

One of my favorites, called Anhanguera, fromBrazil, this animal has a 4 to 5 meter wingspan,a head that is well over a meter long, theneck is not too far off from that The body- it has a big chest but the rest of the bodyis like an afterthought, it’s a tiny thingAnd the hindlimbs are so small that feet willfit in one eye socketWow! I mean, I don’t want to laugh at pterosaurs,but they do have really goofy body ratiosSo much head, and so much neck, and the fartheryou go back, you’re right, it’s like somebody

Ran out of energy and was like, I’ll finishthis laterYeah, my joke is always that they skip legdayThey definitely skipped leg daySo that’s how we think the largest flyinganimal ever took to the skies What I loveabout this is scientists wouldn’t have solvedthis mystery if they hadn’t combined differentkinds of science together Not just paleontology,but aerospace engineering and mechanics and

Computer modeling tooSo it would used to be that we’d have tosit down with the fossils or casts of thefossils because the bones are too delicateto try and figure out how these animals moved,and what we’ve done a lot of lately is CTscanning or laser surface scanning of thebones, and we can study those quantitatively,making computer models so we can test howthese animals might have moved around in theirlifetime

You build that pterosaur inside the computer,put it in a wind tunnel, throw it off of acliff, put it in an attack dive, all kindsof cool stuffWe’ve had people who work on designing glidersand other aircraft come in and look becausewhen they’re trying to find efficienciesand make faster planes and more fuel efficientplanes, looking at the fossil record is somethingwe can applyWe’ve only been working on flight for likea century and a half…

Yeah, we haven’t been working at it verylong!And they had tens of millions of years ofpracticeBut as incredibly adapted as pterosaurs wereto flying, they were no match for a rock thesize of a small city falling out the sky andsetting the atmosphere on fire So unlikebirds, all we know of pterosaurs is from theirbones And honestly, after seeing those bonesup close, I can’t decide if it would bereally cool, or completely terrifying to have

Pterosaurs around todayI think it would depend on which ones I thinki would be perfectly happy seeing a littlefit-in-the-palm-of-my-hand pterosaur perchedon my porch, but, Quetzalcoatlus is circling,we can’t go outside today because it mighteat the kids… that would be…It’s like in game of thrones The dragonswere cute when they were babies, but lateron they became real problem children

I’m kinda glad we got chickens insteadStay curious

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