Pterosaur physiology

[JimC]

Yes.
And when the quick twich fibers run short on oxygen. I don't think anyone knows the exact time and I expect it would vary substantially with species, but my hunch would be 45 seconds to a minute (about the same as us). Long enough to go about 1/2-3/4 mile in no-lift conditions. Keep in mind that they would rarely flap, though very powerful at it when they did.

 

[chornedsnorkack]

10 seconds is the order of magnitude I have seen for flight duration of cocks.
For a modern soarer, see Andean condor:

https://www.researchgate.net/publication/342919401_Physical_limits_of_flight_performance_in_the_heaviest_soaring_bird/download

Just 1% of all flight time spent flapping. Median 8,9 s... but 6 minutes flapping attested.
Cocks and turkeys don´t glide, but they rely on flight to escape flightless predators, cross low obstacles... and fly to roosts.
Did the front and rear limbs of pterosaurs suit perching from roosts in branches?
When they did, did they perch upright on the branch like birds, or hang head down from the perch like bats?

 

[JimC]

"Did the front and rear limbs of pterosaurs suit perching from roosts in branches?"

No, though I expect the smallest ones would be able to.

"When they did,"

They didn't.

"did they perch upright on the branch like birds, or hang head down from the perch like bats?"

More reminiscent of giraffes, though that is a bit of a deliberate exaggeration.

"For a modern soarer, see Andean condor:"

Though quite interesting in their own right, completely different launch and soaring flight style from pterosaurs. That said, I've spent a good bit more time working on Argentavis than Condors. Argentavis is far more interesting, to me at least.

I touched a bit on Argentavis when I was asked to give a presentation at ICVM-7, the International Congress of Vertebrate Morphology.


Birds, bats, and pterosaurs are illuminated as much by their differences as their similarities, so you have to be familiar with all three to talk about any of them.

 

[JimC]

To digress a bit, when looking at flapping flight in birds bats, and pterosaurs, I look at the downstroke and upstroke in 10 time increments each, but with variable percentage of time spent in each. I articulate the wings at each joint plus the spine, applying variable density altitude and HAG (height above ground to allow for the Biot-Savart effect on induced drag). Profile drag for each wing segment is adjusted based on local lift coefficient. The tail and tail loads are adjusted similarly. I usually calculate neck drag and lift as an inclined cylinder similarly to the way it is done for dirigibles. I usually treat head drag by frontal area. I've recently found proof that the azdharchids used a bell lift distribution, so I'll be adjusting the spanwise progression of upwash in high aspect ratio, highly tapered wings to incorporate that when appropriate. The effect isn't huge, but it does provide a noticeable increase in thrust and reduction in drag, without much impact on total lift (makes em glide better)

 

[chornedsnorkack]

"For a modern soarer, see Andean condor:"

Though quite interesting in their own right, completely different launch and soaring flight style from pterosaurs. That said, I've spent a good bit more time working on Argentavis than Condors. Argentavis is far more interesting, to me at least.

I touched a bit on Argentavis when I was asked to give a presentation at ICVM-7, the International Congress of Vertebrate Morphology.

Condor, albatross, turkey and swan are distinguished for being extant and accessible for detailed examination in ways Argentavis, Pelagornis and pterosaurs are not.

 

[JimC]

That's true, but it is very much like attempting to learn more about Ferraris by studying jeeps or a deuce and a half. I would hesitate about trying to force similarities that aren't there. Wouldn't you?

Albatrosses and Frigate Birds are a lot closer to pterosaurs in flight style and much more useful in cross comparisons, but the biomechanics are so different that those differences are more important than the similarities.

In pterosaurs for example, Sesimoid 'A' is critically important to suppination and pronation of the outer wing. Yet I've seen more than one pterosaur 'expert' attempt to seat the pteroid in the Lateral Distal Carpal socket that instead holds the Sesimoid. One of them in addition, even mounted the LDC upside down on the Distal Carpal You just have to shake your head and roll your eyes.

Bird wrists and pterosaur wrists of course are not even remotely similar in structure or operation. They are both interesting though for their differences. Here's a photo of the Quetz right wing LDC and Sesimoid 'A'. Their functions when assembled into the wrist are pretty obvious. I've always been much impressed with the elegant simplicity of the pterosaur wrist and the ways that it accomplishes its multiple functions. You could write a book about pterosaur wrists.

 

[chornedsnorkack]

In addition to the chest muscles moving the whole wing - pectoral muscle for downstroke, various options for upstroke - the bat flight membranes contain plagiopatagial muscles, that do some real work in flight. Birds do not have plagiopatagial muscles.
Did pterosaurs have plagiopatagial muscles like bats?

 

[JimC]

Yes, but they operated differently.
And keep in mind that pterosaur membranes were tension battened, not compression battened.

 

[JimC]

I've noticed that you mostly recommend comparisons with avian thermal soarers or continuous flappers instead of dynamic soarers even though the majority of pterosaurs were dynamic soarers.
What is your reason for doing that?

By the way, since you mention swans, the Whooper Swan Stonker at 44 pounds, in addition to being the heaviest known Swan, is the heaviest known individual bird to fly by means of continuous flapping. He was an amazing animal. Disappeared between Iceland and Scotland in I think 2002 or 2003 (I forget which). The young male traveling with him also vanished during that trip.

 

[JimC]

To give an idea of the relative size of the Quetz torso to the rest of the animal (small morph), here is a preliminary sketch of a quarter scale 4 foot span Quetz intended for an eventual ornithopter design. At the moment, the neck and shoulder cross sections are still just simplified ellipses. This drawing is only intended to show relative torso size - it is not detailed. Notice how narrow the wing is, and the fillet that attaches it to the knee.

 

[chornedsnorkack]

I've noticed that you mostly recommend comparisons with avian thermal soarers or continuous flappers instead of dynamic soarers even though the majority of pterosaurs were dynamic soarers.
What is your reason for doing that?

Trying to reflect on it, the abundance of living big birds in these other groups.
From
List of largest birds - Wikipedia. and related species of similar sizes where revealed by closer examination
looking at the living species that are clearly reputed to fly at takeoff weight over 10 kg...

1. Turkey. Attested to fly at 17,05 kg, span to 144 cm. Clearly a shorthaul flier
2. Trumpeter swan. Attested weight 17,2 kg, span 310 cm. Sustained flapper
3. Mute swan. Attested at 23 kg of dubious airworthiness, span up to 240 cm
4. Whooper swan. Attested weight 15,5 kg, span 275 cm
5. Wandering albatross. Attested weight 16,1 kg, span 370 cm. Dynamic soarer
6. Southern royal albatross. About as big as wandering albatross.
7. Dalmatian pelican. Attested weight 15 kg, span 351 cm
8. Great white pelican. Weight 15 kg, span 360 cm
9. Kori bustard. Alleged weight 20 kg, span 275 cm
10. Great bustard. Weight 21 kg, span 270 cm
11. Andean condor. Alleged weight 14,9 kg, span 330 cm. Thermal soarer.
12. California condor. Alleged weight 14,1 kg, span 305 cm
13. Cinerous vulture. Weight 14 kg, span 310 cm
14. Himalayan vulture. Weight 12,5 kg, span 310 cm
15. Japanese crane. Weight 15 kg, span 250 cm
16. Siberian crane. Weight 15 kg, span 260 cm

This list has a lot of problems with basically the way how the maxima of size are explored and reported in the source data (very inconsistently!). Nevertheless, it shows that among the living birds, sustained flapping (definitely the three species of big swans) is not at a disadvantage: neither thermal soaring (condors and vultures) nor dynamic soaring (two great albatrosses) nor flying shorthaul (definitely turkey, maybe bustards) allows a bird to grow much heavier than a swan.

Do pterosaurs show distribution restrictions from need of windshear, like albatrosses? That is, inability to occur in tropics, and inability to as much as cross it such that the genera diverge across hemispheres?

 

[JimC]

"This list has a lot of problems with basically the way how the maxima of size are explored and reported in the source data (very inconsistently!)."

Typical of lists....

"neither thermal soaring (condors and vultures) nor dynamic soaring (two great albatrosses) nor flying shorthaul (definitely turkey, maybe bustards) allows a bird to grow much heavier than a swan"

Square Cube rule at work (actually, per Paul MacCready it is closer to 2.77 power).
22 foot span and associated weight is about the upper limit for birds due to launch restrictions. Stonker was exceptional with regard to maximum weight.
Pterosaurs sidestep that restriction in two ways

1) membrane wings instead of feathers
2) quadrupedal launch - they don't use flapping as a part of launch; instead doing a standing start quadrupedal leap followed by spreading the wings (running, flapping, and wind aren't required). For that reason, they aren't limited by lift increasing with the square of wingspan while weight increases with the cube (actually about 2.77 power). After launch and spreading the wings, they would transition either to flapping if they need to accelerate, or directly to soaring if they don't. northropi weighed approximately 150kg (330 pounds). That isn't a maximum possible weight for the pterosaurian terrestrial launch, but qualitatively based on the humerus morphological changes required in going from 4.8 meter span to 10.4 meter span (and 20-22 kg to 150 kg), I would be skeptical of any weight for any pterosaur much over 175-200 kg. I first described the terrestrial quad launch in late February 1999 during an hour long talk at SSA99. Chris Bennett suggested the possibility of an arboreal quad launch for small pterosaurs sometime in the 1980s, I forget exactly when. Mike Habib independently recognized the terrestrial quad launch and first reported it in 2005 after asking my permission to do so when I had to cancel my talk due to being unable to attend a Conference. I appreciated his courtesy.

"Do pterosaurs show distribution restrictions from need of windshear, like albatrosses? That is, inability to occur in tropics, and inability to as much as cross it such that the genera diverge across hemispheres?"

Mixed bag, maybe. Quetz hasn't been found in the southern hemisphere, but could also soar thermally or by using cloud streets, so that isn't a restriction for Quetz. I haven't checked other species for distribution across the equator so can't make a definitive statement. Most species (exclusive of the azdharchids) were more lightly loaded than Quetz, so could probably also use thermal soaring. I wouldn't expect the tropics to create a restriction for other pterosaurs but can't give a definitive answer.

 

[JimC]

"Trying to reflect on it, the abundance of living big birds in these other groups".

But why try to force similarities from dissimilar means of energy extraction from the atmosphere?

 

[chornedsnorkack]

Do we have any extant birds who significantly use both dynamic and thermal soaring?
Pelicans are said to use soaring and have second largest span after albatrosses (and ahead of swans).
Albatrosses have small head and neck. Swans have long neck but small head. Pelicans have long neck and long bill... like pterosaurs. Eat fish, too.
I understand that there are pterosaurs with preserved neck joints showing pterosaurs were stiff-necked relative to swans and albatrosses?
Since a pterosaur head is far from its centre of gravity it must have a large lever arm. How much pitch and yaw authority did the head have in flight?

 

[JimC]

"Do we have any extant birds who significantly use both dynamic and thermal soaring?"

You're the one focused on birds, you tell me. And what difference does it make?

"Since a pterosaur head is far from its centre of gravity it must have a large lever arm".

It did, but not much weight, so pitching moment was ameliorated to some extent in long- necked pterosaurs (not all had long necks). And like dirigibles, long necked pterosaurs spun off a pair of longitudinal counter rotating vortices that stabilized along the top of the neck and back, supporting part of their weight in flight. On a medium sized pterosaur, 5 meter span +/- , cg was typically about one and a half inches in front of the shoulder and could be moved fore and aft at will. So could the center of lift. Within reasonable limits, the animal can put either where it wanted them.

"Albatrosses have small head and neck. Swans have long neck but small head. Pelicans have long neck and long bill... like pterosaurs. Eat fish, too".

And your point is....??? BTW, pelican necks are flexible - not analogous. See photo. Azdharchid pterosaurs can't do that. Neither can most others.

"I understand that there are pterosaurs with preserved neck joints showing pterosaurs were stiff-necked relative to swans and albatrosses?"

Did you see the photos of one of our Quetz neck skeletons in max dorsal, ventral, and lateral deflection that I posted earlier? (Post #59)
Each joint had skeletal hard stops that limited deflection so that the total remained within the animals' ability to compensate.

 

[JimC]

Another thing about pterosaurs that folks tend to overlook --
The inboard 'half' of the wing was also the front leg. All joint articulations had to adequately (not optimally) serve both purposes.

 

[JimC]

Back to movies and such...
Greg Paul was the paleo advisor on the pterosaurs in the first 'Jurassic Park' movie. I've seen his pre-production drawings, and they were excellent. Bore no resemblance whatever to the abominations actually included in the movie. Greg was not a happy camper.