Pterosaur physiology
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chornedsnorkack
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You are giving exact accelerations and approximate mass. Would it be useful to expressly specify the loadings of the ground in vertical and horizontal direction? I understand the assumption here is that the ground remains in place - the pterosaur is leaving no trace?
"Would it be useful to expressly specify the loadings of the ground in vertical and horizontal direction?"
No.
Water launch is the other extreme. Launch from mud is somewhere between the two limits and quite variable. As an aside, Quetz water launch technique is much different from Anhanguera.
Re mass, it can vary on the loose order of 30% or so during the course of a single flight as the individual burns off first fat, and then reacts muscle mass with water to burn off excess muscle. Flight ends as dehydration sets in and available internal water is depleted. Some birds can burn off more than 50% of their body weight during a single flight. JAP (Stonker) comes to mind - he was an impressive animal, and the heaviest individual bird known to fly by continuous flapping.
For an individual, launch accelerations vary as mass and wind change. Max acceleration is very similar to the maximum accelerations generated during gust response - on the very loose order of 4.5g.
Another aside, my talk at the Toulouse Conference in September 2001 was titled 'A Skeletal Mechanism With Application to Automatic Gust Load Alleviation in the Azdharchidae'. I figured if I made the title long enough, I could shorten the talk.....
My wife and I flew out on the 10th a couple of hours before the terrorist attack. An interesting trip.
No.
Water launch is the other extreme. Launch from mud is somewhere between the two limits and quite variable. As an aside, Quetz water launch technique is much different from Anhanguera.
Re mass, it can vary on the loose order of 30% or so during the course of a single flight as the individual burns off first fat, and then reacts muscle mass with water to burn off excess muscle. Flight ends as dehydration sets in and available internal water is depleted. Some birds can burn off more than 50% of their body weight during a single flight. JAP (Stonker) comes to mind - he was an impressive animal, and the heaviest individual bird known to fly by continuous flapping.
For an individual, launch accelerations vary as mass and wind change. Max acceleration is very similar to the maximum accelerations generated during gust response - on the very loose order of 4.5g.
Another aside, my talk at the Toulouse Conference in September 2001 was titled 'A Skeletal Mechanism With Application to Automatic Gust Load Alleviation in the Azdharchidae'. I figured if I made the title long enough, I could shorten the talk.....
My wife and I flew out on the 10th a couple of hours before the terrorist attack. An interesting trip.
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"What did adult pterosaurs do for bad seasons - migrate longhaul?"
I'm not exactly sure what you mean by bad season, but a generic answer is that no one really knows. I doubt it, but they were capable of crossing the Atlantic between dawn and dusk of a single day (it was narrower then), so they could if the urge struck them. The flock of the small morph of Quetz was found clustered together on the margin of a highly alkaline lake a couple of hundred miles from the sea. The big guy (northropi) was found about 18 miles south southeast of the flock.
As an aside, all pterosaurs had upper speed limits. The aeroelastic number of their flight membranes declined with lift coefficient (which declined with increasing speed), and they couldn't allow the number to drop below the bistable limit without initiating flutter. I wasn't the first to notice this, but I did validate it with a 10 foot span 60% flying scale model of Anhanguera piscator. Flutter initiation was interesting to watch.
I'm not exactly sure what you mean by bad season, but a generic answer is that no one really knows. I doubt it, but they were capable of crossing the Atlantic between dawn and dusk of a single day (it was narrower then), so they could if the urge struck them. The flock of the small morph of Quetz was found clustered together on the margin of a highly alkaline lake a couple of hundred miles from the sea. The big guy (northropi) was found about 18 miles south southeast of the flock.
As an aside, all pterosaurs had upper speed limits. The aeroelastic number of their flight membranes declined with lift coefficient (which declined with increasing speed), and they couldn't allow the number to drop below the bistable limit without initiating flutter. I wasn't the first to notice this, but I did validate it with a 10 foot span 60% flying scale model of Anhanguera piscator. Flutter initiation was interesting to watch.
chornedsnorkack
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What kind of traces does regular seasonal migration with winter/summer leave in the bones? Like, what happens to the oxygen isotope composition? Strontium etc. isotopes? Are there any bone sections where you can track the growth of the pterosaur and its whereabouts at any time over its life, or at least till growing up/completion of bone growth?
"Are there any bone sections where you can track the growth of the pterosaur and its whereabouts at any time over its life, or at least till growing up/completion of bone growth?"
Very few. The inner edge of the very thin bone wall was constantly resorbing and redepositing, as were the internal struts. In general, there's no record of progressive growth or isotope ratios. And in many (like Quetz), a fungus attacked the interior prior to fossiization and no internal information remains.
Very few. The inner edge of the very thin bone wall was constantly resorbing and redepositing, as were the internal struts. In general, there's no record of progressive growth or isotope ratios. And in many (like Quetz), a fungus attacked the interior prior to fossiization and no internal information remains.
chornedsnorkack
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In level flapping flight, speed was limited by friction anyway. Did pterosaurs have to avoid stooping?
Birds have other reasons not to stoop when they are not intending to (they need to shed their energy).
Birds have feathered wings with permanent camber. One useful maneuver for them is whiffling.
Do bats whiffle? Did pterosaurs?
"In level flapping flight, speed was limited by friction anyway"
It's called drag, not friction (you seem to be thinking only of profile and interference drag, exclusive of induced drag), and no - it isn't what limits level flight speed in pterosaurs. Their speed is limited by aeroelastic number.
They can place their wing skeletons in approximate stoop position, but it would not be a high speed maneuver because the entire wing membrane would be in a severe flutter, very draggy and essentially uncontrollable
They can whiffle, but only to a very limited extent and with a couple of caveats.
1) some birds have enough neck mobility that they can turn their bodies and wings essentially upside down and rotate their necks 180° to place their heads right side up again. Pterosaurs have very limited neck mobility (because they have limited yaw control) and cannot do that.
2) a whiffle is essentially a slip, a cross controlled high drag maneuver that depends upon substantial yaw authority to maintain it. Pterosaurs have very limited yaw authority. If they attempt more than a very, very mild whiffle, they will suddenly diverge into a steepening, descending, tightening spiral that will drop the aeroelastic number below the flutter limit. It is difficult to recover from that. This is why the azdharchid pterosaurs have modifications in phalanges IV-2 & 3 that not only facilitate a bell lift distribution (in lieu of an elliptical distribution), but require it. One purpose of the bell distribution is to generate proverse yaw during turns rather than adverse yaw - pterosaurs have difficulty in compensating for adverse yaw. The bell distribution is also why they shed the induced drag vortices at about 70% of the semispan instead of the wingtip.
Camber is both variable and locally controllable in pterosaurs EXCEPT when the aeroelastic number (due to decreasing lift coefficient with increasing speed) drops first below the bistable limit (at which time the camber on one or both wings can invert, thereby suddenly reversing the direction of lift forces) and then the flutter limit (at which time the membrane becomes uncontrollable and flutter can actually break the outer phalanges). Pterosaurs can survive a break in IV-4, but a break of IV-2 or 3 is invariably fatal.
BTW, I mostly fly antique taildraggers that lack flaps, so I use a whiffle to facilitate descent on almost every landing. I like the whiffle.
It's called drag, not friction (you seem to be thinking only of profile and interference drag, exclusive of induced drag), and no - it isn't what limits level flight speed in pterosaurs. Their speed is limited by aeroelastic number.
They can place their wing skeletons in approximate stoop position, but it would not be a high speed maneuver because the entire wing membrane would be in a severe flutter, very draggy and essentially uncontrollable
They can whiffle, but only to a very limited extent and with a couple of caveats.
1) some birds have enough neck mobility that they can turn their bodies and wings essentially upside down and rotate their necks 180° to place their heads right side up again. Pterosaurs have very limited neck mobility (because they have limited yaw control) and cannot do that.
2) a whiffle is essentially a slip, a cross controlled high drag maneuver that depends upon substantial yaw authority to maintain it. Pterosaurs have very limited yaw authority. If they attempt more than a very, very mild whiffle, they will suddenly diverge into a steepening, descending, tightening spiral that will drop the aeroelastic number below the flutter limit. It is difficult to recover from that. This is why the azdharchid pterosaurs have modifications in phalanges IV-2 & 3 that not only facilitate a bell lift distribution (in lieu of an elliptical distribution), but require it. One purpose of the bell distribution is to generate proverse yaw during turns rather than adverse yaw - pterosaurs have difficulty in compensating for adverse yaw. The bell distribution is also why they shed the induced drag vortices at about 70% of the semispan instead of the wingtip.
Camber is both variable and locally controllable in pterosaurs EXCEPT when the aeroelastic number (due to decreasing lift coefficient with increasing speed) drops first below the bistable limit (at which time the camber on one or both wings can invert, thereby suddenly reversing the direction of lift forces) and then the flutter limit (at which time the membrane becomes uncontrollable and flutter can actually break the outer phalanges). Pterosaurs can survive a break in IV-4, but a break of IV-2 or 3 is invariably fatal.
BTW, I mostly fly antique taildraggers that lack flaps, so I use a whiffle to facilitate descent on almost every landing. I like the whiffle.
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chornedsnorkack
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I see. Even in level flapping/soaring flight...
I see. So pterosaurs have poor maneuverability in flight compared to many recent and contemporary birds and bats?
Do you often find pterosaur skeletons with fractures that fully healed in lifetime?
As you mention, pterosaurs had limited fat reserves and seem to have needed flight to feed efficiently. Full healing of a fracture takes several weeks, yet the process starts earlier. Do you find fossils with partially healed fractures - the pterosaur survived for a few weeks and the bone started healing, but then died of hunger because of inability to use the bone? What other signs of prolonged and fatal illnesses are found in fossil bones?
"I see. So pterosaurs have poor maneuverability in flight compared to many recent and contemporary birds and bats?"
It was pretty good, but not comparable to birds and bats. On the other hand, they could develop far higher lift coefficients. And their maneuverability was good enough to make them effective at dynamic soaring.
"Do you often find pterosaur skeletons with fractures that fully healed in lifetime?"
Not often and only in IV-4.
"Do you find fossils with partially healed fractures - the pterosaur survived for a few weeks and the bone started healinwing.g, but then died of hunger because of inability to use the bone?"
Not that I'm aware of. All the other breaks I'm aware of show no sign of healing.
"What other signs of prolonged and fatal illnesses are found in fossil bones?"
Severe arthritic scarring in the mortise and tenon joint between the distal carpal and metacarpal IV. As an aside, the angular extent of that scarring provides an indicator of the usual amount of pronation and suppination in the outer wing.
It was pretty good, but not comparable to birds and bats. On the other hand, they could develop far higher lift coefficients. And their maneuverability was good enough to make them effective at dynamic soaring.
"Do you often find pterosaur skeletons with fractures that fully healed in lifetime?"
Not often and only in IV-4.
"Do you find fossils with partially healed fractures - the pterosaur survived for a few weeks and the bone started healinwing.g, but then died of hunger because of inability to use the bone?"
Not that I'm aware of. All the other breaks I'm aware of show no sign of healing.
"What other signs of prolonged and fatal illnesses are found in fossil bones?"
Severe arthritic scarring in the mortise and tenon joint between the distal carpal and metacarpal IV. As an aside, the angular extent of that scarring provides an indicator of the usual amount of pronation and suppination in the outer wing.
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Matteo, you remember it correctly, though I personally doubt that the impact triggered or enhanced any of the Deccan eruptions.
Note that on the cover of Memoir 19, 'Lawson' should be italicized but not capitalized. As an aside, Doug Lawson found the Type Specimen of Quetzalcoatlus northropi. He did NOT find the small morph of Quetzalcoatlus lawsoni formerly called Quetzalcoatlus species that was eventually named after him after Wann's death. Wann Langston, Jr was the principal investigator on Quetz, and in near 50 years he never gave Qsp a species name because he couldn't find any diagnostic differences between it and northropi (neither can I, but that's not my specialty). I confess I still tend to call the little critter Q species or Qsp.
Like all these publications, some parts are quite good; others are a bit iffy.
The Cover Illustration is by John Conway. It is quite good with the exception of the headcrest, the position of the eye, and the flight position of the hindlimbs. If you put a Quetz hindlimb in that position, the knees would be sticking out in front of the shoulders (John knew that - he is one of the few who had access to Quetz, and he keeps a hindlimb at home - as do I). I contributed mostly to the biomechanics section.
Note that on the cover of Memoir 19, 'Lawson' should be italicized but not capitalized. As an aside, Doug Lawson found the Type Specimen of Quetzalcoatlus northropi. He did NOT find the small morph of Quetzalcoatlus lawsoni formerly called Quetzalcoatlus species that was eventually named after him after Wann's death. Wann Langston, Jr was the principal investigator on Quetz, and in near 50 years he never gave Qsp a species name because he couldn't find any diagnostic differences between it and northropi (neither can I, but that's not my specialty). I confess I still tend to call the little critter Q species or Qsp.
Like all these publications, some parts are quite good; others are a bit iffy.
The Cover Illustration is by John Conway. It is quite good with the exception of the headcrest, the position of the eye, and the flight position of the hindlimbs. If you put a Quetz hindlimb in that position, the knees would be sticking out in front of the shoulders (John knew that - he is one of the few who had access to Quetz, and he keeps a hindlimb at home - as do I). I contributed mostly to the biomechanics section.
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BTW, one of the features of the flapping stroke that very few people seem to be aware of is that the suppination during the upstroke is actually a pronation relative to the freestream.
And the pronation during the downstroke is actually a suppination relative to the freestream.
This is true of birds and bats as well
And the pronation during the downstroke is actually a suppination relative to the freestream.
This is true of birds and bats as well
chornedsnorkack
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Is it true of insects?
Probably, but I haven't stepped through any insects' flapping cycles to quantify it one way or the other, so can't make a definitive statement. It would have been true for the meganeura, with their higher reynold's numbers and mininised viscous effects.
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chornedsnorkack
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What would be more interesting here is - considering the airspeed and maneuverability of insects, how do you identify adaptations of pterosaurs to hunt insects in flight? Actual stomach contents are rare, but how about mouthparts, wings, maneuverability?
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