Here’s a pterosaur proposal doomed to a crashlanding

I can’t believe
the quad launch hypothesis (Fig. 1)  is still alive… but it is. Perhaps just barely.

Rayfield, Palmer and Martin have an offer
for a budding paleontologist/engineer student designed to frustrate that young talent because they know their conclusion before they initiate experiments and they will not investigate more promising hypotheses.

According to Rayfield, Palmer and Martin (links below):
“The main objective of this proposal is to investigate the effectiveness of the quadrupedal launch [of pterosaurs] and by comparing it with the bipedal launch of birds, test if it was one of the factors that enabled pterosaurs to become much larger than any bird, extant or extinct.” (Fig. 1 – and note: they are not testing the hypothetical quad launch of pteros against the hypothetical bipedal launch of pteros)

Figure 1. Quad launch of giant pterosaur as envisioned by Dr. Emily Rayfield. See text for list of problems.

Figure 1. Quad launch of giant pterosaur as envisioned by Rayfield, Palmer and Martin. See text for list of problems. Note how the pterosaur literally floats off the Earth here, achieving great height, higher than any kangaroo leap from a standing start, prior to the first down stroke of the wings. Note the placement of the fingers in the final frame, unlike the ichnite evidence that shows lateral to posterior orientation of the fingers. Fossils show wing membrane fold to near invisibility prior to flight and the wing membrane is stretched between the elbow and wingtip. Artwork by Colin Palmer.

Choose to accept this assignment and you will be asked to:
“Create anatomical reconstructions of possible azhdarchid morphologies and using kinematic simulation software to create a simple baseline bipedal launch model, validated against published data for birds and humans and tested for sensitivity to assumptions and modeling detail. 

Your reward for doing so:
“The student will join the large and vibrant Bristol palaeobiology community and receive training in anatomical and computational techniques.”

Main supervisor:
Prof Emily Rayfield
Co-supervisor(s):
Dr Colin Palmer (University of Bristol),
Ms Elizabeth Martin (University of Southampton)

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 2. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate. This configuration gets both the legs and the wings working together to build up airspeed prior to takeoff — if possible. This mode also powers rapid running — if flight is not possible.  Note the large mass of thigh muscles here, anchored on the long ilium and prepubes, much larger than the forelimb bones anchored on that small pectoral girdle.

According to Rayfield, Palmer and Martin [objections in bold]
“Pterosaurs adopted a quadrupedal stance 1, which meant that their forelimbs were used for both flight and locomotion, including launch 2, so carried less baggage once airborne 3 Hypothesised quadrupedal launch behaviour provided a long launch stroke and recruitment of large muscle mass to power take-off (Habib 2008) 4; proportionately larger than that available to birds. While the underlying concept of the quadrupedal launch is now widely accepted 5, the kinematic and anatomical details are poorly understood meaning that estimates of available launch power are very imprecise.6, Increasing our understanding of the take-off process will shed new light on the role it played in pterosaur gigantism and to help refine our estimates of pterosaur maximum size.”

“The project will establish the differences between the ground launch dynamics of birds and pterosaurs, how these relate to differences in morphology, scale with and enforce upper limits to size, before ultimately establishing the most effective morphology to maximise launch capability. This will be achieved by creating anatomical reconstructions of possible azhdarchid morphologies and using kinematic simulation software to create a simple baseline bipedal launch model, validated against published data for birds and humans and tested for sensitivity to assumptions and modelling detail. This baseline model will then be modified to incorporate quadrupedal launch morphology. The effect of varying muscle morphologies on power output and the effects of varying size and subsequent allometric relationships will be determined. Finally, anatomically correct simulation models will be constructed to model quadrupedal launch capability and potential upper limits to size.”

Okay let’s take a closer look at those boldface objections

  1. Not all pterosaurs were quadrupedal. We know this from bipedal pterosaur tracks other workers tend to avoid and from reconstructions showing awkward configurations when quadrupedal. The sacrum is reinforced with fusion and additional vertebrae (Fig. 6) to support the lever arm produced by the presacral area in a bipedal configuration. Sister taxa to pterosaurs, including Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama were all either facultative or obligate bipeds.
  2. Take a look at several of the animations pictured in this blog and see for yourself which model makes more sense when gravity is part of the equation. All pterosaurs were built so they could lift their forelimbs from the substrate while keeping balanced over their toes in order to simply walk, to flap their wings prior to flight, to flap their wings for added thrust during terrestrial locomotion, to frighten predators and intimidate rivals, to mate, etc. etc.
  3. The ‘baggage’ referred to here means the hind limbs in birds, which are not used in flight. Pterosaurs used their hind limbs as horizontal stabilizers in flight, as evidence by their uropatagia, and so legs were not ‘baggage,’ but key aerodynamic control and lift surfaces. This hypothesis is ignored by the Rayfield team.
  4. The muscle mass for pterosaur hind limbs has traditionally been underestimated. The Habib model also accepts that the force of quadrupedal launch is transformed down the large wing metacarpal (Fig. 3). Unfortunately ALL known pterosaur tracks show only the tiny three free fingers contact the substrate — and they were not built to transfer the great forces involved in quadrupedal launches. More unfortunately, the Habib figure (Fig. 3) cheats the length of the tiny free fingers, making them smaller still in order to enable the Habib hypothesis.
  5. The quadrupedal launch hypothesis is widely accepted among a very small group of paleontologists based in the South of England. There is no fossil ichnite evidence for quadrupedal launch. No animal larger than a vampire bat is capable of this feat, and they have traits that pterosaurs (and other bats) do not.
  6. This final confession by the Rayfield team is welcome and a long time coming. Pity they are shoving their problem over to a naive student, not well-versed in the history of this problem, unless he/she is a reader of this blog!
The so-called catapult mechanism in pterosaurs

Figure 3. Left: The so-called catapult mechanism in pterosaurs. Note the falsely reduced fingers enabling wing contact with the substrate. Right. The actual pterosaur morphology that keeps the wing off the substrate.

The proposal objective (above) is flawed.
Rayfield, Palmer and Martin want to test bipedal birds vs. quadrupedal pterosaurs, leaving out any study of bipedal pterosaurs. This assumes the validity of the quadrupedal launch a priori to finding hard evidence for it in the fossil record. Ignoring and deleting competing hypotheses and data is something we’ve seen from other pterosaur workers, also from southern England. Their must be some sort of factor of influence there.

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 4. Unsuccessful Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Pteranodon attempting a quadrupedal take-off
(Fig. 4) cannot open its wing fingers, which are like long bamboo poles held against the back of the wrist when quadrupedal, fast enough to open the wings before the first downstroke and gravity causes a crash — even if given one heck of a leap in a quadrupedal mode – a leap no kangaroo could match.

On the other hand
when Pteranodon starts with wings ready for the first downstroke at the moment of hind limb leap, then all the forces Pteranodon can muster are at play at the moment of take-off. A little more take-off speed could be added with a short, speedy, lizardy sprint while flapping for thrust and airspeed (Fig. 2).

Successful heretical bird-style Pteranodon wing launch

Figure 5 Successful heretical bird-style Pteranodon wing launch in which the hind limbs produce far less initial thrust because the first downstroke of the already upraised wings provides the necessary thrust for takeoff in the manner of birds. This assumes a standing start and not a running start in the manner of lizards. Note three wing beats take place in the same space that only wing wing beat takes place in the widely accepted wing launch model of Habib (2008).

There is nothing wrong with a bipedal Pteranodon
I modeled one myself (Fig. 6). There is something wrong with a pole-vaulting Pteranodon, trying to lift its wings off the ground while at the same time forcing them against the substrate, rotate them parasagittally to the open position, extend the wings horizontally, lift the wing tips above its head, then apply the downstroke, all before crashing on its face. Evidently several English workers have invested far too much time and pages in the academic literature to turn back now. Professional pride is at stake and no one will notice if some of the evidence is overlooked and avoided.

Standing Pteranodon

Figure 6. Standing Pteranodon. Note the high number of sacral vertebrae here to support the long lever arm of the presacral area.

References
Project description
Earls KD 2000. Kinematics and mechanics of ground take-off in the starling Sturnis vulgaris and the quail Coturnix coturnix. Journal of Experimental Biology 203, 725 – 739.
Habib  MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana B28, 159-166.
Heers AM and Dia KP 2014. Wings versus legs in the avian bauplan: Development and evolution of alternative locomotor strategies. Evolution 69, 305-320.
Witton MP 2013. Pterosaurs: Natural History, Evolution, Anatomy (Princeton University Press, Princeton.

Project enquiries
Email: e.rayfield@bristol.ac.uk
Contact number: 0117 394 1210
Host institution: University of Bristol
CASE Partner: Ginko Investments Ltd

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Walking azhdarchid movie matched to pterosaur tracks

Earlier Pterodactylus, a small pterodactylid pterosaur, was animated to match Craysaac tracks (Fig. 1). In this model the backbone is elevated higher here than in some of the wireframe pterosaurs you may have seen (Fig. 3) and the forelimbs carry little if any of the weight. Nevertheless, in this species they work like and impress like ski poles — doing the pterosaur walk.

Pterodactylus walk matched to tracks according to Peters

Figure 6. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

Today, Zhejiangopterus (Cai and Wei 1994), a large azhdarchid pterosaurs, is similarly animated to match large Korean pterosaur tracks (Hwang et al. 2002; Fig. 2).

Note how Zhejiangopterus carries its head, with the middle ear region above the center of gravity, like a human. At any point Zhejiangopterus could lower its skull for a meal or a drink. It could also raise its wings without shifting its balance to initiate a bipedal takeoff. Note how little the forelimbs actually touch the substrate. Again, this is the ski-pole hypothesis in which the forelimbs are used mainly to steady the pterosaur, not to generate thrust or support the weight (exception noted below).

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.)

Figure 2. The large azhdarchid pterosaur, Zhejiangppterus. is shown walking over large pterosaur tracks matched to its feet from Korea (CNUPH.p9. Haenamichnus. (Hwang et al. 2002.) The feet are planted just as the hands are lifted. Click to enlarge and animate if not moving.

The troubles with the horizontal backbone model are at least threefold

  1. The skull would be far from the center of gravity at the end of a long neck. Bearable, perhaps, in tiny Pterodactylus. unwieldy on giant Zhejiangopterus with its oversized skull.
  2. The forelimbs would bear most of the weight with the skull far beyond them. This is fine when floating and poling.
  3. Standing up to open the wings for display or flight would involve throwing the skull backward to end up standing bipedally. Awkward. Time consuming. The competing quad launch hypothesis is out of the question as reported earlier here and elsewhere for the reasons listed therein.
Figure 3. The horizontal backbone hypothesis for quadrupdal pterosaurs. This hypothetical model is supposed to match tracks, but the tracks can be matched to a genus and species, so why not use it?

Figure 3. The horizontal backbone hypothesis for quadrupdal pterosaurs (Mazin et al. 2009). This hypothetical model is supposed to match tracks, but the tracks can be matched to a genus and species, so why not use it? Click to enlarge. Note the massive bending of the wrist here. Completely unnecessary. 

Mazin et al. (2009) published a series of imagined wireframe pterosaurs matched to the tracks (Fig 3). This is odd because a former champion of bipedal pterosaurs was co-author Kevin Padian, who was a quad ptero-track denier for many years until the Craysaac tracks won him over (while continuing to deny the pterosaur nature of other tracks. Odder still because the animation that was used for the public (which I saw year ago and not sure if it is still in use, but is not used here) showed a more upright Pterodactylus.

Note: The published wire frame model might match the gait and placement of the ptero tracks, but the manus and pes of the wireframe model are but a small fraction of the size of the tracks. This is something the authors and their referees missed, or overlooked. But we all know, the devil is in the details.

“If the glove doesn’t fit, you must acquit.” — Johnny Cochran at the OJ Simpson murder trial.

And if the feet and hands don’t match,
you’ve got the wrong wire frame pterosaur model. Contra Mazin et al., I took the effort to match the manus and pes track to an extinct taxon. In Science, you must use the data as precisely as you can, and let those data tell you, as closely as possible, how to build your model. Don’t walk in with your pet hypothesis and try to shoehorn or BS your way through it, unless you can get away with it, as Mazin et al. did until now.

Figure 4. Zhejiangopterus at a stage in its walking cycle in which the right manus bears nearly all the weight.

Figure 4. Zhejiangopterus at a stage in its walking cycle in which the right manus bears nearly all the weight. M. Habib noted the arm bones were much stronger than they needed to be for flight. Well, maybe that’s because Zhejiangopterus was walking on its forelimbs. Birds don’t do that. BTW that’s the same force vector Habib imagined for his ill-fated quad takeoff. I hate to say it, but this pose makes more sense in every way.

If my model of pterosaur walking is correct,
and I’m sure it has minor flaws that may never be known, then the tiny manus bears nearly the entire weight of the pterosaur at one and only one brief point in the step cycle (Fig. 4) that does not need support in normal bipedal walking. The tiny area of the tiny fingers is likely to impress deeper because the weight of the pterosaur is concentrated on a smaller area (compared to the long foot) in contact with the substrate. This pose also might answer Mike Habib’s original mystery as to why the pterosaur humerus was built stronger than it needed to be for flight. Birds don’t put their weight on the forelimbs. And few bats do (the tiny vampire is the exception).

Here are the alternative models 
for pterosaur quadrupedal standing (Fig. 5) for ready comparison. Which of these provides a bended knee with the proper vectors for thrust? The manus doesn’t have to and didn’t provide thrust, but it should not have been placed so far forward that it could only provide a braking vector to the shoulder.

Click to enlarge. Averinov re-published images of Zhejiangopterus and Quetzalcoatlus from Witton 2007 and Wittion & Naish 2008 that demonstrate a certain devil-may-care attitude toward the anatomy, especially in Quetzalcoatlus. There was little regard for the the shape of the pelvis in both images and little regard for the lengths of the cervical elements and robust pectoral girdle in Q. My images, on the other hand, were traced from photos taken during a visit to Texas several years ago.

Figure 5. Click to enlarge. Averinov re-published images of Zhejiangopterus and Quetzalcoatlus from Witton 2007 and Wittion and Naish 2008 that demonstrate a certain devil-may-care attitude toward the anatomy, especially in Quetzalcoatlus. Moreover, just imagine the long lever problems these two have with that long extended neck while walking and the tremendous strain put on that forelimb, which is not angled correctly to provide thrust. It don’t provide thrust in the more upright pose either, but it doesn’t need to. In that case it merely provides some stability.

On the other hand, a feeding pterosaur in water might have looked something like this (Fig. 6).

Quetzalcoatlus scraping bottom while standing in shallow water.

Figure 6. Quetzalcoatlus scraping bottom while standing in shallow water. Here the hollow and airy skull is nearly weightless or even buoyant in water. 

 

References
Cai Z and Wei F 1994. On a new pterosaur (Zhejiangopterus linhaiensis gen. et sp. nov.) from Upper Cretaceous in Linhai, Zhejiang, China.” Vertebrata Palasiatica, 32: 181-194.
Hwang K-G, Huh M, Lockley MG, Unwin DM and Wright JL 2002. New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, southwestern Korea. Geology Magazine 139(4): 421-435.
Mazin J-M, Jean-Paul Billon-Bruyat J-P and Padian K 2009. First record of a pterosaur landing trackway. Proceedings of The Royal Society 276:3881–3886.
online pdf 
Unwin D and Lü J. 1997. 
On Zhejiangopterus and the relationships of Pterodactyloid Pterosaurs, Historical Biology, 12: 200.

wiki/Zhejiangopterus

Dimorphodon pterosaur takeoff – revised

Earlier I produced an animated GIF that showed how Dimorphodon could not have taken off using its forelimbs (Fig. 1; contra Witton 2013). At the same time I produced an animated GIF that showed how Dimorphodon could have taken off using its hind limbs with wings still folded (modified Fig. 2), noting that back then I preferred to use the wings, but wanted to show how powerful the hind limbs were. For some reason I waited until today to offer an animated GIF in which the wings open prior to takeoff and together with the hind limbs initiate a power launch with maximum thrust (Fig. 3), just like birds.

Click to animate. Witton's Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, pushes the pterosaur down. There's just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap.

Figure 1. Click to animate. Witton’s Dimorphodon in the process of leaping. Note the wings are in the upswing at the apex of the leap. The opposite and equal reaction, along with gravity, pushes the pterosaur down. There’s just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap.

Figure 2. Click to animate. Dimorphodon hind limb leap - like a frog. But note the takeoff does not take advantage of available wing thrust until later. At the dip in the leap wing thrust takes over. The wings probably flapped faster than shown.

Figure 2. Click to animate. Dimorphodon hind limb leap – like a frog. But note the takeoff does not take advantage of available wing thrust until later. At the dip in the leap wing thrust takes over. The wings probably flapped faster than shown.

Figure 3. Click to animate. Dimorphodon hind limb leap - like a bird or a frog. There's nothing wrong with this method. It gets the wings open right away to provide thrust and lift at the apex of the hind limb portion of the leap. The thighs are massively muscled, more so than the forelimbs. The extension and flexion of the toes provide that last little umph! to the take-off, as in frogs and kangaroo rats. And let's remind ourselves, pterosaurs were fully capable of bipedalism and leaping, as shown here.

Figure 3. Click to animate. Dimorphodon hind limb leap – like a bird or a frog. There’s nothing wrong with this method. It gets the wings open right away to provide thrust and lift at the apex of the hind limb portion of the leap. The thighs are massively muscled, more so than the forelimbs. The extension and flexion of the toes provide that last little umph! to the take-off, as in frogs and kangaroo rats. And let’s remind ourselves, pterosaurs were fully capable of bipedalism and leaping, as shown here.

Which takeoff method is less risky? Uses larger muscle groups? Is replicated by living taxa? And falls in line with basal nonvolent taxa (like Sharovipteryx and Longisquama)? Why not use the wing thrust to ensure getting airborne? That’s what birds and bats do…

And why are paleontologists embracing this heretical idea and giving it the status of paradigm? Now the ‘normal’ takeoff, like a bird, is considered heretical.

Figure 4. Dimorphodon fingers. Yellow added for keratin extensions. M. Witton suggests that these claws are inappropriate for grasping and so doesn't mind placing Dimorphodon into a quadrupedal pose, making everything awkward to impossible from that point on. These claws look trenchant to me, ideal for clinging to tree bark  or other similar substrates.

Figure 4. Dimorphodon fingers. Yellow added for keratin extensions. M. Witton suggests that these claws are inappropriate for grasping and so doesn’t mind placing Dimorphodon into a quadrupedal pose, making everything awkward to impossible from that point on. These claws look trenchant to me, ideal for clinging to tree bark or other similar substrates.

Today’s blog post was inspired
by one produced by Dr. M. Witton in response to the Jurassic World movie, who noted, “The hands and feet of Dimorphodon are also robust, and equipped with large, trenchant claw bones (these, of course, provide the specific namesake, ‘macronyx’). There are indications that the extensor muscles controlling these might have been powerful, as every claw on both hands and feet is equipped with a neighbouring sesamoid – those intra-tendinous bones serving to enhance muscle output or protect tendons against powerful joint motion. Interestingly, the only other animals with these claw-adjacent sesamoids are lizards and a ‘bottom walking’ fossil stem-turtle – more on that another time. As with all pterosaurs, there is no indication that their hands or feet were for grasping, and their claws are really nothing like talons (take that, Jurassic World website).”

If I’m reading this correctly 
Dr. Witton doesn’t consider ‘trenchant’ (= penetrating) claw bones to be anything like ‘talons,’ which typically are unguals that penetrate prey. The feet of pterosaurs are indeed not made for grasping (screaming tourists, etc.), but the wing claws of Dimorphodon were ideally set up for vertical landings on tree trunks. When the wings are adducted the palmar side of the unguals face each other like clapping hands and could have readily grappled a tree trunk like a lineman, penetrating the bark with its talons. This is taken to the extreme in the related pterosaur, Jeholopterus and the bird-like dinosaur, Velociraptor, which had similar stiff fingers supporting feathers and trenchant claws – ideal for grappling, but not grasping.

Earlier we looked at
pterosaur hands here in the first of a seven-part series. The variety you’ll see will show you that pterosaur fingers and claws evolved for several environments and uses.

References
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.

Pterosaur launch talk from 2012 on YouTube

Dr Mike Habib
gave a one-hour talk on pterosaurs and his hypothesis of forelimb takeoff back in 2012 when the idea was novel.. That talk was uploaded to YouTube here. In counterpoint back then we discussed Habib’s forelimb launch hypothesis for pterosaurs here and here. We’ll continue with that discussion today.

Habib reports
that he does not believe or is not aware of flightless pterosaurs, but I think he was aware of Jme-Sos 2028, which was in ReptileEvolution in 2011 and entered the literature in 2013. Habib does not believe in bipedal pterosaurs, despite bipedal tracks. He notes a tendency to produce giant flyers, but actually they quite rare with regard to taxon number, and were only present in the latest Cretaceous. Habib does not recognize tiny pterosaurs as adults and he does not believe in multi-modality (walking disconnected from flying), despite fossil evidence for disconnected hind and forelimbs. Habib did not discuss pterosaur origins.

Habib used CT scanning
for figuring out the inner and outer diameter of long pterosaur bones. The bone is thinner than in birds, about the proportions of a cardboard paper tube. Key to Habib’s hypothesis, he notes the forelimbs are stronger than the hind limbs in pterosaurs. He notes the hind limbs of pterosaurs are average-to-weak compared to birds. Furthermore, Habib reports that take-off in birds is ‘hindlimb’ driven with takeoff initiated 80-90% by leaping, the rest with a downbeat. Even in hummingbirds with their tiny legs and feet the ratio is 50-50.
Habib notes that initial lift is difficult in all flying creatures. The vampire bat uses its forelimbs to catapult itself 2 feet vertically before flapping. That is several times its standing height. He notes launch speed is related to wing loading (wing area/weight), which can increase substantially after a meal, which brings us to…
Quadrupedal launch in pterosaurs
As discussed several years ago at various posts (see above) unfortunately Dr. Habib ignores the literature on bipedal pterosaur tracks and the origin of pterosaurs from long-legged and bipedal fenestrasaur precursors. Late in the talk he gives credit to Dr. Padian, who championed bipedality among pterosaurs, but omly imagined bipedal ancestors, and had nothing to do with discovering fenestrasaurs. When you make all pterosaurs ungainly quadrupeds, shackled by a membrane that connects wing tips to ankles, you put pterosaurs at an unnatural and completely imagined disadvantage. Habib also imagined short manual digits that enabled digit 4 to act like grasshopper hind limbs to catapult them into the sky.
All pterosaurs were capable of bipedal locomotion.
They could balance with their feet beneath their armpits, like birds do. Quadrupedal ptero tracks were all produced by a few clades of beachcombing pterosaurs during their browsing mode. All of these had relatively small wing claws. Other pterosaurs had much larger trenchant manual claws, ill-suited for contact with the ground.
With regard to forelimb launch,
all of the animated pterosaurs that Dr. Habib approved appear to be helium filled as the first down flap comes a long time after the initial launch. Moreover, none of the animations show the pterosaur leaping several times its standing height, as in the vampire bat. Worse yet, the giant wing fingers, which initially are folded posteriorly during the forelimb leap need to be extended prior to or at the acme of the leap, but initially there is no airspace to do this. Based on the orientation of the ventral orientation of the forelimbs during launch and recoil, the wing finger has to extend ventrally in the plane of the wing, This is hazardous to the swinging wing tip if it contacts the launch pad. The ground gets in the way unless the pterosaur is high enough to avoid this. All pterosaur takeoff animations authorized by Dr. Habib appear to glaze over this point, as if the long wing finger had no mass or moment arm and the initial leap never experiences recoil in the ventral plane. Rather the wings imeediately pop out effortlessly. Even a lightweight fishing rod takes a little time and effort to get from one point to another. As a suitable analog, imagine doing a leaping pushup high enough to extend and produce a downflap with fishing rods rotating ventrally in both hands. Much better to flap and run from the start for maximum ground speed and thrust.
If a heavily muscled 6’ tall kangaroo
cannot initially leap its own height, or more, from a standing start, it seems unikely that a larger pterosaur can do this in the manner of tiny vampire bats. Size matters.
Large birds flap with great effort to get their mass off the ground or water. That seems to be a good model for large pterosaurs as well.
Quetzalcoatlus running like a lizard prior to takeoff.

Figure 10. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

AMNH animated pterosaur takeoffs

On YouTube the American Museum of Natural History (AMNH) has placed two new pterosaur take-off sequences in their video, “Meet the Paleontologists,” part of last year’s pterosaur exhibit. One snippet features Jeholopterus (Fig. 1) and the other features Quetzalcoatlus (Fig. 2). Both purport to demonstrate the forelimb take-off method that Mike Habib’s team present here and I critiqued here and here.

IMHO, pterosaurs, like birds used multiple downbeats of their powerful wings to create thrust and lift as shown here.

Th AMNH snippets takes the opposite tack,
that pterosaurs used their folded forelimbs to push them off the ground, supposedly, but not quite like a vampire bat, (no height is generated at lift-off) and fractions of moments later, they unfold their wings and glide upward (!!!), evidently tossing out the effects of gravity and drag and the need to add thrust, forward momentum and airspeed. The originator of this hypothesis, Mike Habib, appears in the AMNH video. So I assume he had some input. I can’t image that Mike would approve these, as they break several rules of physics, as noted above.

Because the camera moves
in each animation, in both video snippets frames were realigned to remove that camera movement. If you’ve read this far without seeing the videos, refresh the page to start them over.

GIF movie 1. Jeholopterus. Each frame is 5 seconds and there are 7 frames. Click to animate if necessary.

GIF movie 1. Jeholopterus. Each frame is 5 seconds and there are 7 frames. Click to enlarge and animate if necessary. It recycles only once. As this movie starts with the page opening, you may wish to refresh the page.

The animated Jeholopterus (GIF move 1)
does not leap skyward with its spring-like forelimbs then unfold its wings like a vampire bat. Rather it simply leans forward off the rock with hind limb thrust, glides while unfolding its big wings then produces an upbeat before a downbeat. Not sure how it managed to rise during the upbeat. It must be a bubble in a breeze. All that thrust prior to the first downbeat had to come from the original hind limb push-off, but they gave Jeholopterus such puny legs. Nothing here makes sense.

GIF movie 2. Quetzalcoatlus take off. Each frame is 5  seconds. 7 frames total. Recycles once. Click to animate and enlarge if necessary.

GIF movie 2. As this movie starts with the page opening, you may wish to refresh the page. Quetzalcoatlus take off. Each frame is 5 seconds. 7 frames total. Recycles once. Click to animate and enlarge if necessary. Here the giant animal appears to rise and accelerate without one downbeat of its wings. Watch the shadow to see where the wings are in the middle frames.

In the Quetzalcoatlus movie (GIF movie 2
there is indeed a recoil prior to takeoff, but once again the leap doesn’t elevate the pterosaur. Rather the pterosaur again appears to be light as a bubble as it rises only after opening its wings without a downbeat, then accelerates and rises. Where does all this thrust come from?

In the alternate hypothesis
(Fig. 3), Quetzalcoatlus flaps its wings while gaining airspeed with its legs, as in many large birds. So plenty of airspeed is generated from both sets of limbs and the wings are already extended and beating like crazy prior to takeoff.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 1. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate. The difference between this wing in dorsal view and the wing in figure 2 come down to the angle between the bones.

Key to the AMNH pterosaur problems
is their inability to imagine pterosaurs getting up on their hind limbs and standing bipedally to flap their wings like birds. Yet if they did their reconstructions in strict accordance with the bones they would find that pterosaurs could balance themselves on their hind limbs — even those that left quadrupedal imprints. We know this because their feet extended as far forwards as their center of balance, at the wing root, their shoulder joints — even those that walked quadrupedally. Pterosaurs were quite capable in every mode they found themselves in, from flying, to walking, to swimming. They weren’t awkward, as commonly portrayed.

The second problem with the AMNH animations
is their lack of faith in the thrust of the each downbeat of the wing. Bats do it. Birds do it. Why not let pterosaurs do it? Pterosaurs had to toss down a lot of air to get airborne, especially when they did not have sufficient forward airspeed to generate lift with Bernoulli’s principle. No matter how hollow their bones are, pterosaurs are not bubbles!

Quetzalcoatlus in dorsal view, flight configuration.

Figure 2. Quetzalcoatlus in dorsal view, flight configuration. The hind limbs were not uselessly trailing. They were extended laterally acting like horizontal stabilizers on an airplane — and they contributed to lift, but not thrust.

The third problem
is their lack of accuracy in their reconstructions. Beside the bone issues, the hind limbs should be extended laterally in flight where they contributed to lift and acted like horizontal stabilizers. The AMNH did not get the ‘blueprint’ right for either pterosaur. All they needed to do is pay attention to the details — and remember it takes a lot of power to overcome gravity.

Figure 4. Jeholopterus in dorsal view. Here the robust hind limbs, broad belly and small skull stand out as distinct from other anurognathids. Click to enlarge.

Figure 3. Jeholopterus in dorsal view. Here the robust hind limbs, broad belly and small skull stand out as distinct from other anurognathids. Click to enlarge.

People are also bitching about the Jurassic World dinosaurs, but that’s a franchise that wants to sell merchandise and the original merchandise did not have feathers on their ‘raptors’. On the other hand, the AMNH is a museum. They should have the resources and experts to get things right in flight technique and morphology.

 

Largest flying creature ever video on YouTube

Let’s start the new year off
with a new/old pterosaur video on YouTube. This is a reedited version of the earlier National Geographic Sky Monsters video reviewed earlier.

Figure 1. National Geographic pterosaur documentary on YouTube. Click to view.

Figure 1. National Geographic pterosaur documentary on YouTube. Click to view.

Quetzalcoatlus is featured, of course.

So is Margot Garritsen, a Dutch engineer and Stanford professor who leads a team intent on building a flying pterosaur based on Paul Sereno’s ornithocheirid from the Sahara. They were counting on greater success with lighter materials and a more accurate wing movement for flight control.

According to the video
we have no idea where they come from. Actually we’ve known this for 14 years. More academically published data is being suppressed, unfortunately. But you can find out more here.

Dino Frey (Natural History Museum of Karlsruhe) is featured with a giant ‘wing bone’ from Israel having only a cylindrical body without articular ends. Looks to be about 8 inches in diameter, more than 8 feet long (60-foot, 18 m wingspan or twice the size of Quetzalcoatlus). It made the news here and here. Giant pterosaurian footprints from Mexico appear to confirm the size, all discovered prior to 2005, still not published.

On that note:
Mark Witton reported on the DML in 2008, “However, subsequent reappraisals of the alleged discoveries suggested that the footprints belong to a large theropod dinosaur and the ‘wing bone’ is, in fact, a particularly large piece of fossil wood (E. Frey, pers. comm. 2007), suggesting claims of 20 m flying reptiles were somewhat premature.”

Yes, even PhDs sometimes make mistakes. And later in the video the giant pterosaur ‘bone’ is confirmed as wood. Other problems you’ll no doubt recognize. Lot’s of bad and speculative propaganda here.

Some good data from Kevin Padian on pterosaur landings. You can see an earlier  animation here, but the video has a new one in 3-D.

 

 

 

Breeze: important for takeoff. Acrobatic leaping : not so much.

Pterosaur take-off analog
In this video of a glider with legs you can see it just takes a long set of wings and a stiff breeze to become airborne – not an elaborate acrobatic forelimb leap sequence. This is a good model, a good niche and a good location, for ornithocheirid and pteranodontid pterosaurs to rest, nest and take off. The invisible, but very present breeze is key to this aerie. It provides the lift. Gravity, when the nose of the aircraft is pointed down, provides the thrust.

 Click to play 48-second video of glider launching by airspeed alone caused by a stiff breeze.

Figure 1. Click to play 48-second video of glider launching by airspeed alone caused by a stiff breeze. This should put to rest all thoughts for the necessity of a dangerous and odd forelimb leap for pterosaurs, especially the big winged ones, the ornithocheirids and pteranodontids. As in airplanes, forward speed is increased by tipping the nose down.

But wait! There’s more!
Pterosaurs, of course, provided their own thrust when they flapped. So, really, why go through goofy acrobatics when all you have to do is stretch out and flap those big wings!

I mean, really!!
It’s this simple and much less risky than the alternative.