Anhanguera animation at the NHM (London)

This one started off with so much promise
as the animators at the National History Museum (NHM) in London assembled their version of the ornithocheirid pterosaur, Anhanguera, bipedally (Fig. 1), as you’ll see when you click on the video under ‘References’.

Figure 1. Animated by the NHM, Anhanguera is bipedal and flapping its literally oversize wings.

Figure 1. Animated by the NHM, Anhanguera is bipedal and flapping its literally oversize wings standing on oversize feet with an undersized skull and hyperextended elbows and unbalanced stance.

Unfortunately there were some morphology issues (compared in Fig. 2):

  1. wings too long
  2. sternal complex missing
  3. gastralia missing (but rarely preserved in ornithocheirids)
  4. feet way too big
  5. skull too small
  6. tail too short
  7. not sprawling
  8. free fingers too big
  9. wing fingers should tucked tight against elbows (in the same plane)
  10. one extra cervical
  11. anterbrachia too short and gracile
  12. elbows overextended (in Fig. 1)
  13. too much weight put on forelimbs, center of balance (wing root) should be over the toes
  14. Prepubes are extremely rare in ornithocheirds, but when present they are tiny, putter-shaped and oriented ventrally in line with the bent femora, not anteriorly
Figure 2. NHM Anhanguera compared to skeletal image from ReptileEvolution.com.

Figure 2. NHM Anhanguera compared to skeletal image from ReptileEvolution.com. There are at least 10 inaccuracies here. See text for list.

Also unfortunately, the video quickly devolved
to the invalid and dangerous quad launch, when (doggone it!) it was all set up to do a more correct and  much safer bird-like launch. The laws of physics and biomechanics are ignored here, but at least David Attenborough narrates.

Figure 3. NHM Anhanguera quad launch select frames.

Figure 3. NHM Anhanguera quad launch select frames. The laws of physics and the limitations of biomechanics are ignored here.

Attempts to convince readers and workers
that the quad-launch hypothesis cheats morphology and physics (as recounted here and at links therein) have so far failed. But I’m not giving up. So, if anyone has a connection to the NHM in London, please make this post available to alert them of their accidental foray into wishful thinking and inaccurate morphology.

References
National History Museum (NHM) in London

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“Why we think giant pterosaurs could fly” (…NOT!)

Yesterday the Dinosaur Mailing List
linked a MarkWitton.com blogspot.com post titled, Why we think giant pterosaurs could fly.” It’s worthwhile looking (once again) at the arguments Dr. Witton most recently put forth to test them against the evidence presented by pterosaurs here at PterosaurHereseies. After all, it’s not fair to dredge up arguments Dr. Witton may have long ago abandoned. Alas, Dr. Witton is holding fast to his old arguments and pet hypotheses, many of which paint a false picture of pterosaur biology and behavior, based on evidence to the contrary (see below).

Dr. Witton precedes his arguments
with the admission that, “Giant azhdarchids are invariably known from scant remains, sometimes a handful of fragments representing bones from across the skeleton or, in the case of Quetzalcoatlus northropi, an incomplete left wing.” We looked at Q. northropi wing elements earlier here (Fig. 1). They are indeed scant, but nevertheless, impressive.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 1. Quetzalcoatlus specimens to scale. Q. sp. is also enlarged to the humerus length of Q. northropi. Gray zones are hypothetical and/or restored. Reduction of the wing, even in the smaller species, argues against flight in giant azhdarchid pterosaurs, as it does in much smaller flightless pterosaurs.

 

Dr. Witton reports,
…just a few bones can betray volant habits. It’s evident that even the largest pterosaurs bore wing anatomy comparable to their smaller, incontrovertibly flightworthy relatives. The huge deltopectoral crest…is a clear correlate for powered flight in giant species.” 

Unfortunately
Dr. Witton does not acknowledge the presence of any flightless pterosaurs (taxon exclusion). Flightless pterosaurs could test Dr. Witton’s ‘dp crest clear correlate’ hypothesis. Three flightless pterosaurs have been reported here based on their relatively short wings: SoS2428, PIN 2585-4, and Alcione (Fig. 2). Notably, all three have an unreduced deltopectoral crest.

Figure 2. Flightless pterosaurs, SOS24248, PIN2584-4, Alcione, to scale.

Figure 2. Flightless pterosaurs, SOS24248, PIN2584-4, and Alcione, to scale. Reducing the span of the wing is the easiest and most common way to become flightless in pterosaurs.

Wing length vs body size
provides the best argument for flightlessness in the case of SoS2428 (Fig. 3), itself a pre-azhdarchid. The same argument works for the other two flightless pterosaurs when comparisons to flighted sisters are presented.

Lateral, ventral and dorsal views of SoS 2428

Figure 3. Lateral, ventral and dorsal views of SoS 2428 alongside No. 42, a volant sister taxon. In dorsal view it becomes very apparent which one would be flightless.

Arthurdactylus

Figure 4. Arthurdactylus in dorsal view. Note the rather small deltopectoral crest in this taxon.

It’s a good time to remember
that hatchling pterosaurs had adult proportions. They were able to fly shortly after hatching. This also means that small to tiny pterosaurs had wing/body ratios comparable to those of the largest incontrovertibly flying pterosaurs, the ornithocheirids (Fig. 4) and pteranodontids. Notably, the deltopectoral crest of the ornithocheirid, Arthurdactylus, is relatively smaller than one would predict using Witton’s hypothesis, and quite variable in other members of this clade.

Dr. Witton reports,
“for large azhdarchids: their functional morphology and trackways show strong terrestrial abilities and they probably spent a lot of time grounded, only flying when harassed, or wanting to move far and fast. Indeed, in all likelihood giant pterosaurs couldn’t launch every few moments.”

Unfortunately
Dr. Witton does not consider the possibility that large azhdarchids could have employed wing thrust to hasten their getaways on the ground, like many large birds do (Fig. 5).

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 5. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate.

Witton and Habib 2010
used software designed to model bird flight to predict that giant azhdarchids could fly faster than 90 kph and were easily able to sustain long distance glides.

Witton reports: “The key to everything: quad launch”
and provided a helpful illustration (Fig. 6) to show the moment of takeoff. Remember, in pterosaurs the wing finger never makes an imprint, so the three tiny free fingers must bear some multiple of the entire weight of the pterosaur at the moment of lift-off, then the ventrally-oriented wing finger must circle around to provide at least one upward lift and one downward flap before the otherwise inevitable crash. Not even a heavily muscled kangaroo can lift itself to such a height on the first leap. Not even a body builder can perform such a push-up… but a tiny vampire bat can, and does so routinely.

Figure 6. In the 'quad launch' hypothesis, for which there is currently no fossil imprint evidence, the pterosaur does a sort of leaping push-up using its tiny free fingers to bear a multiple of its entire weight during the acceleration, without flapping, to takeoff speed.

Figure 6. In the ‘quad launch’ hypothesis, for which there is currently no fossil imprint evidence, the pterosaur does a sort of leaping push-up using its tiny free fingers to bear some multiple of its entire weight during the acceleration, without flapping, to takeoff speed. Then the dangerous part begins. The pterosaur has to swing its wings up and down to creat aerial thrust before crashing (see figs. 7, 8). The short humerus provides little leverage to do this. Among tetrapods, only tiny highly derived bats are able to succeed with this sort of takeoff scenario. All other pterosaurs flap first, then fly.

What happens
if pterosaurs don’t make altitude every time they attempt a launch? (Fig. 7) Calamity (Fig. 8). There is no room for error, no evolutionary path to perfection, even if possible. Can one enhanced pushup provide the necessary airspeed and altitude without wing assistance? Witton and Habib think so? Look what those giant wings have to do before contributing to thrust and lift. Much better to get those wing providing thrust and lift at the moment of takeoff, rather than waiting until, perhaps, too late.

Successful Pteranodon wing launch based on work by Habib (2008).

Figure 7. Successful Pteranodon wing launch based on work by Habib (2008). Best case scenario.

 

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 8. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Successful heretical bird-style Pteranodon wing launch

Figure 9. 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 wing 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 and time that only one wing beat takes place in the Habib/Molnar model.

 

re: the pelvis
Witton reports, “The avian skeleton has two large girdles for limb muscles: an enlarged shoulder and chest region for flight muscles, and an enhanced pelvic region to anchor those powerful hindlimb launch muscles. Pterosaurs, in contrast, have only one large limb girdle – their shoulders, making this the de facto likely candidate for powering their launch cycles.”

Standing Pteranodon

Figure 10 Standing Pteranodon (the Triebold specimen). Note the robust and extended pelvis supported by at least nine sacrals.

It may be traditional to discount the pelvic region
of pterosaurs, but in all cases, the pelvis is also enhanced (Fig. 10) with fused sacrals, prepubes and an anteriorly expanded ilium anchoring powerful, and under appreciated muscles.

Ignoring evidence that does not serve a pet hypothesis.
Witton ignores the hard evidence of bipedal pterosaur trackways, when he quotes Habib 2008, who “also notes that launch in living tetrapod fliers correlates to terrestrial gait: the number of limbs used to locomote on the ground is the same as the number used to take-off. Birds walk and launch with two legs, while bats walk and launch using all four. An extensive record of pterosaur trackways shows that pterosaurs were quadrupedal animals like bats, and it stands to reason that they also launched from four limbs: they would contrast with our living fliers if they had to shift gaits to take off.” 

Witton calls the quad-launch
“the most efficient launch mechanism conceivable for a tetrapod,” ideal for such a strong humerus and such a weak femur. Julia Molnar produced a video of a quad launch.  You might remember that the Molnar pterosaur free fingers were incorrectly reduced (Fig. 11) and relocated to the dorsal (in flight) surface of the wing in order to get that big wing finger on the ground and ready to snap like a grasshopper’s hind limb. Yes, they cheated the anatomy to make their pet hypothesis work… and Dr. Witton warmly embraced, rather than pointing out its faults.

The so-called catapult mechanism in pterosaurs

Figure 11a. Left: The so-called catapult mechanism in pterosaurs. The fingers are in the wrong place and cheated small in order to let the wing finger make contact with the substrate – which never happens according to hundreds of pterosaur tracks. Right. The actual design of pterosaur (in this case Anhanguera/Santandactylus) fingers. Click to enlarge.

Errors in the Habib/Molnar reconstruction of the pterosaur manus

Figure 11b. Errors in the Habib/Molnar reconstruction of the pterosaur manus

 

The infamous animation by Molnar
(click to play YouTube video) apparently assumes a nearly weightless mass, a super powerful pushup, and a suspension of the moment of inertia required to drag that big pool stick of a wing finger around to the flying position after it has just been oriented ventrally to say nothing about the effects of drag while opening that less than aerodynamic wing membrane. Isn’t it better to completely extend that wing and set it in the upward position before launch?

Summary of points ignored by Dr. Witton

  1. The largest flying pterosaurs have the largest/longest wings
  2. Flightless pterosaurs do exist and they are identified by their short wings
  3. Flightless pterosaurs retain a large deltopectoral crest and continued flapping to provide thrust for fast getaways and threat displays
  4. The quad launch hypothesis was built on the false premise of wing finger contact with the substrate
  5. The quad launch is dangerous for its participant every time they perform it. Much better to generate wing thrust at the moment of takeoff, not some time later. Such takeoffs can be aborted or diverted without the danger of a crash landing.
  6. The quad launch hypothesis works well for small  bats, ankle high to a Dimorphodon (Fig. 12), which fly in a different fashion from other volant tetrapods, but this ability does not scale up well for giraffe-sized or other pterosaurs.
  7. Dr. Witton cherry-picks the data that fits his hypotheses and ignores data that invalidates the last few years of his work.
  8. Given the paucity of data at present for giant azhdarchids, it would have been appropriate to restore Q. northropi as flightless AND volant, and tell us where the dividing line would be if the missing bones were one way or the other, making comparisons to smaller azhdarchids and to other fully volant large pterosaurs, like ornithocheirids and pteranodontids.
  9. It would have been professional and appropriate for Dr. Witton to alert us to the (perhaps inadvertent) cheating Molnar and Habib did to their pterosaur manus (Fig. 11) before some rank amateur brought it to our attention, and not to adopt this bogus and untenable idea with such gusto (Fig. 6), perhaps out of friendship.
Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It's more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Figure 12. Dimorphodon and Desmodus (the vampire bat) compared in size. It’s more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters.  Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours, especially with giant finger claws.

At what stage(s) did azhdarchids lose the ability to fly?
If we just look at wing length (reduction of distal elements) then this clade appears to have become flightless at least twice (Fig. 13). In both instances that happens when the wing finger tip is no higher (when folded) than the dorsal rim of the dorsal vertebrae. And that happens the second time when azhdarchids double in size to standing over a meter tall. If valid, then the doubling and doubling in size of azhdarchids was possible because they gave up aerial pursuits in favor of a fully terrestrial and/or wading niche, as in the many giant flightless birds we are more familiar with.

Azhdarchids and Obama

Figure 13. Click to enlarge. Here’s the 6 foot 1 inch former President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as our former President. The doubling and doubling again in size was made possible by giving up the constraints of flying. 

 

References
Habib MB 2008. Comparative evidence for quadrupedal launch in pterosaurs. Zitteliana, 159-166.
Witton MP and Habib MB 2010. On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PloS one, 5(11), e13982.

markwitton-com.blogspot.com/2018/05/
Seven problems with the quad launch hypothesis

Pteranodon quad hopping water takeoff, according to the AMNH

Hopefully this is going to be the last time
the American Museum of Natural History embarrasses itself with bogus pterosaur tricks. We looked at problems from the original 2014 AMNH pterosaur display here and elsewhere. Evidently they have decided to stop using math, physics and modern analogs, alas, to their disgrace… while cartooning (Fig. 1) the bird-like pterosaurs under the guise of a scientific exhibition.

Figure 1. GIF animation from the American Museum of Natural History showing how their Pteranodon managed to hop off the surface of the water until suddenly able to flap and fly. Totally bogus.

Figure 1. GIF animation from the American Museum of Natural History showing how their Pteranodon managed to hop off the surface of the water until suddenly able to flap and fly. Totally bogus. It won’t develop any lift or thrust with wings folded. …Unless Pteranodon was filled with helium?? Those deep chord wing membranes are likewise not preserved in any fossil. 

Above is how the American Museum of Natural History
(AMNH) imagines the takeoff of Pteranodon from calm seas (Fig. 1, AMNH webpage). Not credible. Not accurate, either with those deep chord wing membranes, not yet found in any fossils.

Pelican take-off sequence from water.

Figure 2. Pelican take-off sequence from water. Click to enlarge.

Above is how the living pelican
(Pelecanus) actually takes off from gulf waters (Fig. 2 and YouTube video above it in slow motion, click to view). The Pteranodon-like pelican lifts its great wings out of the water to develop lift and thrust. Ground effect keeps it out of the water after one flap. Water is where drag occurs. And legs kicking or hopping has never lifted any pelican out of the water. The wings, fully extended as taut airfoils, do 99% of the work. The foot hops off of wave tops after flight has been initiated, are negligible thrust producers.

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Figure 3. Triebold Pteranodon in floating configuration. Center of balance marked by cross-hairs.

Above is how ReptileEvolution.com
imagines Pteranodon floating on the sea (Fig. 4) using its air-filled wing bones as lateral floatation devices. The torso and skull were also lighter than an equal volume of water, as in all floating birds.

Pterosaur water launch

Figure 4. Ornithocheirid water launch sequence in the pattern of a pelican launch. LIke ducks, geese and pelicans, pterosaur probably floated high in the water. Here the wings rise first and unfold in an unhurried fashion, keeping dry and unencumbered by swirling waters. Then the legs run furiously, like a Jesus lizard, but with such tiny feet, they were not much help in generating forward motion. The huge wings, however, did create great drafts of air, thrusting the pterosaur forward until sufficient airspeed was attained, as in the pelican.

Earlier we looked at several water take-off scenarios
for pterosaurs using Anhanguera as a model (Fig. 4). Keep those wings out of the water where they can develop thrust and lift with full extension and taut membranes. A sagging wing membrane (Fig. 1) develops neither lift nor thrust.

Successful heretical bird-style Pteranodon wing launch

Figure 5. Click to play. 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 wing 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 and time that only one wing beat takes place in the Habib/Molnar model. Compare to a similar number of wingbeats in the pelican.

Above is how the heretical hypothesis
imagines the takeoff of Pteranodon from the ground (Fig. 4): just like a crane, pelican or other large bird. For a water takeoff, just add water and keep the wings off the surface. Flapping so close to the water takes advantage of ‘ground effect’ where lift is increased when the wing is close to the ground.

By contrast,
either the AMNH model is made of helium or hung on a string, or the sea is made of jello, because against all laws of physics somehow those tiny fingers and feet are keeping the head and torso above the watery surface. If anyone can defend the AMNH scenario, please make comment below.

Just found out: The quad fly hypothesis goes back to 1943!
Daffy Duck in “To Duck or Not to Duck” was using the quad style to fly (Fig. 6) back in 1943, just before Elmer Fudd fired a shotgun at him. Compare this technique to Pteranodon in figure 1 and you’ll see convergence on a massive scale.

Figure 8. Daffy Duck in "To Duck or Not to Duck" 1943 uses the quad fly method. See figure 1 for comparable take-off technique.

Figure 8. Daffy Duck in “To Duck or Not to Duck” 1943 uses the quad fly method. See figure 1 for comparable take-off technique.

At the AMNH
Dr. Mark Norell, curator and chair of the Museum’s Paleontology Division, oversaw the pterosaur exhibition with Dr. Alexander Kellner of Museu Nacional in Rio de Janiero.

 

 

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

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

Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It's more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

Figure 3. Dimorphodon and Desmodus (the vampire bat) compared in size. It’s more difficult for larger, heavier creatures to leap, as the mass increases by the cube of the height. Size matters. And yes the tail attributed to Dinmorphodon, though not associated with the rest of the skeleton, was that long. Note the toes fall directly beneath the center of balance, the shoulder glenoid, on this pterosaur, And it would have been awkward to get down on all fours.

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 8. Dimorphodon take off (with the new small tail).

Figure 2, 3. Dimorphodon take off (with the new small tail).

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.