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DrScottHartman — Toothless Wing
Published: 2012-08-26 19:03:13 +0000 UTC; Views: 10603; Favourites: 200; Downloads: 0
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Description
No, I haven't finally gone mad; I was commissioned to do two pterosaurs as part of a larger project I'm working on. The first is Pteranodon longiceps, which in many ways is the quintessential pterosaur to my mind. I've posed it taking off from the quad-launch position at a fairly low energy angle of attack (i.e. a leisurely takeoff, not one used when a theropod is bearing down on you).I'll probably be adopting this as a pose for any future pterosaur reconstructions I do, along with the convention of using 75% gray for the wing membranes. That said, I don't have any current plans to explore pterosaurs beyond this and the one coming next week at this point in time; luckily you already have some excellent pterosaur paleontographers on DA and the web.
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Comments: 58
wow this one is unexpected!
I've read an article about this way of taking off, but I didn't think it was possible.
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Not only possible, but very likely the way all pterosaurs took off.
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Really? It seemed to me that it's strange that they'd propell themselves in the air and then flap with the arms, I thought they wouldn't have time to make the first flap. But maybe I am thinking about how birds do it too much, pterosaur anatomy is different...
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Very different - both birds and pterosaurs have to off the ground enough to let their wings flap (obvious I know, but bear with me); Birds still have those powerful theropod limbs with giant drumsticks and massive thighs, but pterosaurs don't have that. Their forearms are far stronger than their hind limbs, and looking at bone strength in pterosaurs you see the same thing (the forearm bones can take massive loading pressure, while the hind leg bones are far weaker than what you see in birds).
Pterosaurs would be stuck too close to the ground if they tried to leap with just their hind legs, but with quad-launching their hind legs still contribute going from the crouch to the vault phase, but the most powerful muscles and bones in their body are powering them off the last bit - and it's probably the only way a pterosaur like Pteranodon could get enough momentum to get high enough to start flapping.
In case you haven't seen it before, Mike Habib had a grad student do an excellent animation of it here: [link]
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Pterosaur and bird anatomy do have their differences, but the basic laws of physics apply to both. I've watched that animation many times and it makes less sense each time. The math does not add up; the wing upstroke at full speed is shown to be as fast or faster than the stroke speed of a hummingbird. If its musculoskeletal and cardiovascular system could handle this without injury as a matter of course, these creatures could have slapped an adult T-rex off a piss pot and made it thank them for the favor. It does not parallel a vampire bat launch, the axial skeleton angles will cause a stall, and where is the room for a downstroke? Julia's magical levitation does not convince me.
Unless it is launching into a strong headwind, this poor pterosaur is going to be a ptero-sore, with a very dirty beak. Or off a cliff. Seen a vid of a stork launching off a chimney. No room for running, so what does it do? Jumps with the legs to clear the chimney, then drops, to gain soaring/flight speed.
Even if the stall speed was fantastically low for a 250 kilogram azhdarchid, like 5 mph, this arm launch style would likely mean lawn dart imitations for these creatures. 
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wow that's amazing. It really makes more sense now. thanks.
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