SVP abstracts – Ornithocheirid hip range of motion (ROM)

Griffin et al. 2019 report on their study
of the Coloborhynchus (Figs. 3) pelvis during a hypothetical launch. We looked at this issue earlier here following publication of Witton and Habib 2010.

From the abstract:
“Pterosauria includes the largest animals to achieve powered flight. How medium to large-sized pterosaurs were able to launch into the air is a matter of debate.”

Oh, no. Not this invalid hypothesis again. Griffin et al. believe that giant azhdarchids could fly. They could not. Look how short their wings are compared to volant giant seabirds, pteranodontids and ornithocheirids (Fig. 1).

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Griffin et al. continue:
“Birds employ their legs to accelerate their bodies into the air, but the difficulties large birds face in becoming airborne suggests take-off may limit the maximum size of birds. It has been suggested that pterosaurs employed their fore and hindlimbs in take-off, the so-called quadrupedal launch mechanism, overcoming the size constraint.”

That suggestion is not documented in the fossil record. Quad launch is not only dangerous, it is untenable and clearly inferior to using both the wings and legs to produce massive amounts of thrust as large volant birds do. Flightlessness in man-sized and smaller birds made possible flightless giant birds. The same was true for pterosaurs. All the giant pterosaurs had clipped wings (vestigial distal phalanges).

Unsuccessul Pteranodon wing launch based on Habib (2008).

Figure 2. Unsuccessul Pteranodon wing launch based on Habib (2008) in which the initial propulsion was not enough to permit wing unfolding and the first downstroke.

Griffin et al. continue
“Range of motion (ROM) studies are a common way of determining the viability of hypothetical poses in extinct animals. Here we use ROM mapping of the hip joint of a mid-sized pterosaur, Coloborhynchus (SMNK PAL 1133. Fig. 2) to test whether the joint surfaces of the acetabulum and femur were capable of achieving a bipedal and/or a quadrupedal stance during the range of motion required for take-off.” 

Figure 2. GIF animation showing stages in the bipedal take off of Coloborhynchus. Please imagine the wings talking their first mighty flap at the moment of takeoff, relieving the hind limbs from most of the stress.

Figure 3. GIF animation showing stages in the bipedal take off of Coloborhynchus. Please imagine the wings talking their first mighty flap at the moment of takeoff, relieving the hind limbs from most of the stress. In the invalid quadrupdal pose, note the proximal wing finger makes an impression, which never happens in pterosaur tracks.

Griffin et al. continue:
“Using the software programs Maya and MATLAB, possible intersections and orientations between different bones of the hip joint were identified and coded as viable or unviable. Osteological ROM mapping reveals a quadrupedal stance is more likely in launch, with maximum crouch during quadrupedal launch and flight positions being possible.”

See, they had a preconceived bias and did not comparatively test the bipedal configuration. Remember, in the bipedal pose the wings are ready to provide thrust BEFORE the legs launch the pterosaur into the air (Fig. 3). So the legs are not working alone. By contrast in the quad launch scenario, the wings are not unfolded, and not raised above the shoulders when the pterosaur is at the apogee of whatever feeble take-off abducting the antebrachium can provide (Fig. 2).

Figure 1. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221.

Figure 4. The as yet undescribed SMNS PAL 1136 specimen is much larger than comparable bones in the new specimen, MPSC R 1221. This is a resting pose. When walking or preparing to flap the wings would have to rise off the substrate. This sort of giant-winged, small footed, volant creature rarely landed, IMHO.

Griffin et al. continue:
“However, it is important to consider not just osteological ROM but also the effects of soft tissues. ROM simulations can approximate the effect of different soft tissue such as ligamentous constraints and joint cartilage. We find that the required orientation for bipedal launch was not possible without the presence of cartilage. In order to achieve a bipedal stance in this specimen, a minimum of 3 mm of cartilage is required to sufficiently increase the ROM.”

3mm. That’s not very much, and well within the range of possibilities for a large pterosaur. I look forward to seeing their bipedal launch configuration. Having dealt with pterosaur workers cheating morphology to support their bias (e.g. Elgin, Hone and Frey 2011), I’m always suspicious  based on reputation and history.

“A ROM study that included ligaments in addition to cartilage reduced the available viable orientations. This ROM generated in this study does not rule out the possibility of a quadrupedal launch in pterosaurs, and provide greater support for the quadrupedal rather than the bipedal launch hypothesis.”

These authors mistakenly believe that pterosaurs were archosaurs. Testing reveals they are lepidosaurs (Peters 2007). Ligament issues need to based on lepidosaur pelves and hind limbs, not archosaur. Did the authors sprawl the femora, matching femoral head axis to pelvic socket axis? Having built several pterosaur skeletons, I can tell you, the bipedal stance works best. The ROM at the hips is the LEAST of their worries if they are trying to launch a pterosaur with ventrally folded wings.


References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Griffin BW et al. 2019.
Simulated range of motion mapping of different hip postures during launch of a medium-sized ornithocheirid pterosaur. Journal of Vertebrate Paleontology 2019.
Peters D 2007.The origin and radiation of the Pterosauria.Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
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. https://doi.org/10.1371/journal.pone.0013982

The Times (UK) declares: proof for ‘winged dinosaurs’ vaulting

According to The Times.co.uk,
“Isle of Wight find proves winged dinosaurs took off by ‘vaulting’ into the air. Following the discovery of a fossilised giant pterosaur, scientists may have resolved how the 650lb beasts took flight. The sheer size of such creatures has long baffled scientists because they seem too heavy to take off. Now research with a computerised 3D model suggests they used their massive leg and wing muscles to catapult themselves into the air.”

Figure 1. Image from The Sunday Times (UK) showing the Isle of Wight and an ornithocheird filled with helium on a smaller planet taking off by vaulting.

Figure 1. Image from The Sunday Times (UK) showing the Isle of Wight and an ornithocheird filled with helium on a smaller planet taking off by vaulting. See figure 2 for the 650 lb Hatzegopteryx. The human silhouette (gray at left) is way too small for this ornithocheirid, so they got their pterosaurs mixed-up.

“Robert Coram, a professional fossil hunter who made the find, said: “It might have been the largest flying creature that had ever lived up to that time.”

“Mr Habib explained: “Mathematical modelling indicates that launching from a quadrupedal stance — pushing off first with the hind limbs and then with the forelimbs — would have provided the leaping power giant pterosaurs required for takeoff.”

FIgure 2. From The Sunday Times (UK) showing a human to scale with a restoration of Hatzegopteryx.

FIgure 2. From The Sunday Times (UK) showing a human to scale with a restoration of Hatzegopteryx.

This article appears to follow a Witton 2019 SVPCA abstract
(coincidence?) discussing the flight capabilities of the giant azhdarchid, Hatzegopteryx, using Graphic Double Integration and Principal Component Analysis. AND this article coincides with a Scientific American cover story on pterosaurs by Dr. Habib, discussed earlier here.

The pterosaur experts talking to The Times are still not discussing
the much smaller phylogenetic ancestors of azhdarchids with longer wings, nor do they consider the reduced to vestigial distal phalanges that essential clip the wings of azhdarchids over 1.8 m (6 ft) tall, nor do they recognize the traits that attend small flightless pterosaurs.

Let’s stop promoting giant volant pterosaurs
until these objections are met and resolved. Perhaps a little backtracking and apologizing for earlier grand standing is in order here.

Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 3. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Let’s define giant pterosaurs
as those at least 2m or 7ft tall at the eyeball (sans crest if present). The rest are large (more or less human-sized) pterosaurs (comparable to Pelagornis, Fig. 4) or smaller pterosaurs comparable to some other extant bird (e.g. goose-, robin- or hummingbird-sized).

Figure 1. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

Figure 4. Click to enlarge. The largest flying and non-flying birds and pterosaurs to scale.

You might remember
an earlier post featuring a classified ad from U of Leicester, (UK) seeking a student to prove the vaulting pterosaur hypothesis by finding appropriate pterosaur tracks. The Isle of Wight includes several strata with dinosaur tracks. Perhaps someday they will deliver giant pterosaur tracks that suddenly end. Then we can argue if the pterosaur flew from that point on and how it did so.


References
Witton M 2019. You’re going to need a bigger plane: body mass and flight capabilities of the giant pterosaur. SVPCA abstracts.
Counter arguments based on facts appear here:

New Scientific American cover story: Pterosaurs were monsters of the Mesozoic skies

Cover of Scientific American featuring article by Michael Habib.

Cover of Scientific American featuring article by Michael Habib. There are many things wrong with this image and Habib’s article.

Dr. Michael Habib reports,
online for Scientific American, “Fossils and mathematical modeling are helping to answer long-standing questions about these bizarre animals.”

Conspicuously absent from that subhead:
phylogenetic analysis, perhaps because that’s not Habib’s strong suit.

Figure 1. Chase Stone illustration from pterosaur article demonstrating how helium-filled giant azhdarchids on a smaller planet took flight.

Figure 1. Chase Stone illustration from pterosaur article demonstrating how helium-filled giant azhdarchids on a smaller planet took flight. Note now long it takes to perform the first downstroke. Figure 8 shows what would really happen in such a quad launch.

Habib begins with the widely agreed upon basics.
He reports, “Many possessed heads larger than their bodies, making them, in essence, flying jaws of death. No animal in the Mesozoic would have been safe from their gaze.” So, no exaggeration or hyperbole here. Just fulfilling the cover story headline. 

“All that paleontologists know about pterosaurs comes from the fossil record. And that record has been frustratingly fragmentary, leaving us with just a glimmer of their former glory and a host of questions about their bizarre anatomy and ill fate.” Again, another wild statement without the glimmer of reality. We have a rather complete cladogram of pterosaurs with no gaping holes in the fossil record.

“One of the enduring mysteries of pterosaurs is how the largest members of this group became airborne.” Simple answer: they were flightless. Get used to it.

Habib confessess, “After all, it seems unfathomable that birds of such sizes could fly (although this would be puzzling given their many anatomical adaptations for flight).” Simple answer: Their smaller ancestors with relatively longer wings flew.

Figure 2. Pterosaur artwork from SciAm Habib article. Frames 2 and 3 show accurate skeletons. Compare wing proportions of Quetz sp. with ornithocheirid.

Figure 2. Pterosaur artwork from SciAm Habib article. Frames 2 and 3 show accurate skeletons. Note the clipped wings of Quetz. sp. comparee to wing proportions of similarly-sized ornithocheirid. The wings of the big Quez look large enough to fly. but not when compared to other pterosaurs.

Habib reports, “Membrane wings, such as those of pterosaurs and bats, produce more lift per unit speed and area than the feathered wings of birds. This additional lift improves slow-speed maneuvering capability, which for small animals helps with making tighter turns and for big animals facilitates takeoff and landing.”

Habib continues, “Flying animals do not flap their way into the air or use gravity to take off from an elevated location such as a cliff.” Judge this statement after remembering all the flapping birds and bats you’ve ever seen taking off. The first thing they both do is open up their wings (Fig. 3).

Successful heretical bird-style Pteranodon wing launch

Figure 3. 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.

Then Habib goes around the bend, “Many birds can manage impressive leaps. They are constrained by their heritage as theropod dinosaurs, however: like their theropod ancestors, all birds are bipedal, meaning they have only their hind limbs to use for jumping. Pterosaurs, in contrast, were quadrupedal on the ground. Their wings folded up and served as walking, and therefore jumping, limbs.” Therefore? How many animals leap with their folded wings or forelimbs? I have only seen a tiny grounded vampire bat (at 1.2 ounces) do this. But bats push large pulses of air down with their umbrella-like wings when they fly. Action = reaction, not high-pressure below vs. low pressure above, as in soaring birds and pterosaurs.

Anhanguera taking off

Figure 4. Anhanguera taking off in a plantigrade bipedal configuration according to Chatterjee and Templin 2003.Ridiculous.

It’s always fun to pull out
a bad study when trying to prove your point. Habib does this by recalling Chatterjee and Templin 2003 (Fig. 4)  in which “the animal could not weigh more than 165 pounds and had to run downhill into a headwind.”

Habib reports, “What really confuses scientists and enthusiasts alike is not the wings of pterosaurs but the heads. The skull on a rather typical Cretaceous pterosaur might be two or even three times the body length (usually taken as the distance between the shoulder and hip). Some had skulls surpassing four times the length of their bodies. In some species the neck is triple the length of the torso, with the head size triple again, such that the head and neck could make up more than 75 percent of the total length of the pterosaur. Why would any animal be so ridiculously proportioned? And how could such a body plan possibly work for a flying creature?” 

Habib argues against flight in giant azhdarchids when he confesses, “…it is the disproportionate effect that the skull weight has on the animal’s center of gravity. A huge head, especially if mounted on a huge neck, moves the center of gravity quite far forward.” (Fig. 2). “For a typical walking animal, this creates a serious problem with gait: the forelimbs have to move into an awkward forward position for the animal to be balanced.” Not so. We see the same thing in living storks (Fig. 5). They stand upright with their center of balance always beneath the wing root.

Figure 1. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Figure 5. Estimating giant azhdarchid weight from estimated height and comparables with similar smaller taxa.

Habib reports, “Imagine using crutches to walk while minimizing the weight on both legs—you would advance both crutches simultaneously and let them bear all your weight, then swing your legs forward between them, touch down and repeat.” Now imagine using all your power to use your arms and crutches to leap 10 feet into the air to unfold your giant wings. Try as you might, you can’t do it. Neither could pterosaurs, even if they maintained balance over their wing roots (Figs. 6, 7).

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

 

Pterodactylus walk matched to tracks according to Peters

Figure 7. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

Habib reports, “During takeoff, incidentally, the legs would have pushed first, followed by the arms, for a perfect one-two push-off.”

Not often. Perhaps never. And in the real world would have been awkward and dangerous (Fig. 8).

Habib reports, “This arrangement would not have made for the most efficient walking gait, but it was doable. And anyway, pterosaurs traveled primarily by flying.” Don’t you hate it when scientists lump every sort of pterosaur into the same bad habits and niches? Clearly ctenochasmatids and azhdarchids had different habits than anurognathids. BTW, Habib never introduces us to the three known types of flightless pterosaur, including the plover-sized SoS 2428 in the azhdarchid lineage.

Unsuccessul Pteranodon wing launch based on Habib (2008).

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.

Then Habib pulls his most famous ‘rabbit out of the hat’
by failing to show what happens the moment after the pterosaur quad launch (Fig. 9) while cheating contact between the fourth metacarpal and the substrate AND moving metacarpals 1-3 to the top of the metacarpal 4, instead of in front (medially) as in all other tetrapods and pterosaurs (Fig. 9).

Figure 9. Quad launch hypothesis from Habib's SciAm article. He cheats the position of metacarpals 1-3 and does not show what happens after the leap.

Figure 9. Quad launch hypothesis from Habib’s SciAm article. He cheats the position of metacarpals 1-3 to the dorsal surface of metacarpal 4 and does not show what happens after the leap. Think how high this pterosaur has to jump to open up that ventrally oriented giant wing finger. Example in figure 8 above.

If you’re at all interested,
here (Fig. 10) is the real folding mechanism on the same genus of pterosaur manus. Note the placement of fingers and metacarpals 1-3. Habib’s hypothesis depends on a snapping of the wing, like a grasshopper’s leg, produced through contact between the wing finger tendon and the substrate, which is impossible given pterosaur anatomy and hand prints which only show fingers 1-3 making an impression with digit 3 often pointing posteriorly beneath the wing finger (Fig. 10).

Figure 10. Above in color: Earlier image with shorter free fingers from Habib. Below: Tracing from bone photos for comparison.

Figure 10. Above in color: Earlier image with shorter free fingers from Habib. Below: Tracing from bone photos for comparison.

Habib discusses the solution to the center-of-gravity (balance) issue
in giant azhdarchids by angling the wings somewhat forward to match it. Of course, this is not necessary if the giant azhdarchid is forever flightless. The continuing problem with Habib’s hypothesis that he keep ignoring is the FACT that the distal phalanges of giant azhdarchids are reduced to vestiges, effectively clipping the wings. He also cheats the anatomy (Figs. 9, 10) and never acknowledges that issue.

Habib concludes with the widely held hypothesis
that only large pterosaurs existed 65 million years ago, too large to survive the impact extinction. He does not compare Late Cretaceous pterosaurs to Late Jurassic tiny Solnhofen pterosaurs that survived that extinction event.


References

https://www.scientificamerican.com/article/pterosaurs-were-monsters-of-the-mesozoic-skies/

New pterosaur hatchling video from Dr. Witton misinforms

A new video
from Dr. M. Witton looks at the possibility of gliding in hatchling pterosaurs. Unfortunately it is full of misinformation.

Distinct from what Dr. Witton is telling us,
pterosaur hatchling and juvenile proportions are not much different than their 8x larger adult forms. See link below and this growth series image: https://pterosaurheresies.wordpress.com/2015/12/15/pterodaustro-isometric-growth-series/

From the hatchling Pterodaustro image,
Dr. Witton has omitted the skull and neck, but it is present in the egg (it has to be!) and is nearly identical to that of the adult. We looked at a second embryo earlier here (Fig. 2), and for the first embryo see:  http://reptileevolution.com/pterodaustro-embryo.htm for details.
Figure 3. Rough reconstruction using color tracings. Note the elongate jaws and small eye, documenting isometric growth in this pterosaur, as in all others where this can be seen.

Figure 2. Rough reconstruction using color tracings. Note the elongate jaws and small eye, documenting isometric growth in this pterosaur, as in all others where this can be seen.

Relatively large hatchlings
were able to take flight shortly after hatching. True. The eggs were carried within the mother until ready to hatch, as in many lepidosaurs. The eggshell membrane is also lepidosaurian.
In direct contrast,
the fly-sized hatchllngs of tiny pterosaurs had to grow to a size at which they could leave their damp leaf litter environs, or suffer from desiccation based on their surface-to-volume ratio, as in the tiniest living lizards.  See: https://pterosaurheresies.wordpress.com/2011/08/11/the-tiniest-pterosaur-no-6/
Figure 4. Two of the smallest pterosaurs that both have a large sternal complex. BMNH42736 and B St 1967 I 276.

Figure 3. Two of the smallest pterosaurs that both have a large sternal complex. BMNH42736 and B St 1967 I 276.

Gliding is not an option
for baby pterosaurs hatching on the ground. Pterosaurs and their ancestors were flapping before they could fly. Gliding is an ability acquired later in large derived taxa, the same as in birds.
FIgure 8. Dimorphodon take off (with the new small tail).

FIgure 4. Dimorphodon take off (with the new small tail).

The quadrupedal launch
shown in several illustrations is not only bogus, but dangerous and inefficient for the pterosaur. Much better to use the giant flapping wing for thrust from the first moment of take-off. For details: https://pterosaurheresies.wordpress.com/2011/07/20/seven-problems-with-the-pterosaur-wing-launch-hypothesis/
Figure 8. A larger view of Nemicolopterus. Pedal digit 5 is relatively reduced here.

Figure 5. Nemicolopterus. This tiny taxon is close to Sinopterus, but closer to Shenzhoupterous. 

Dr. Witton discusses a Sinopterus dongi hatchling.
He is considering tiny adult Nemicolopterus (Fig. 5) a hatchling. The Nemicolopterus specimen has traits distinct from Sinopterus and nests separately in a cladogram closer to Shenzhoupterus, whereas all other adult/hatchling pairs nest together in a pterosaur cladogram. See: http://reptileevolution.com/nemicolopterus.htm
Figure 1. The new small Pteranodon wing, FHSM 17956, compared to Ptweety and the adult NMC41-358 specimen.

Figure 6. The new small Pteranodon wing, FHSM 17956, compared to Ptweety and the adult NMC41-358 specimen.

We know of not one, but two Pteranodon juveniles.
For details: http://reptileevolution.com/pteranodon-juvenile.htm
For all future and present paleontologists reading this blog.
It is vitally important that you back up your hypotheses with evidence. Don’t cherry-pick or cherry-delete data to fit your notions or fool an audience.

Flugsaurier 2018: Web-footed little pterosaur MB.R.3531

Flugsaurier 2018 part 4
Since the purpose of the symposium is increase understanding of pterosaurs, I hope this small contribution helps.

Figure 1. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx to scale.

Figure 1. Aurorazhdarcho primordial and the smaller Aurorazhdarcho micronyx to scale.

Habib and Pittman 2018
bring us a rarely studied Berlin pterosaur, MB.R.3531 (Fig. 1) originally named Pterodactylus micronyx, then Aurorazhdarcho micronyx. This specimen nests with other wading pterosaurs, Aurorazhdarcho, Eopteranodon and Eoazhdarcho forming  a clade overlooked by other workers, at the transition between germanodactylids and pteranodontids, not related to azhdarchids.

FIgure 1. Reconstruction of MB.R.3531, nesting with Eoazhdarcho, Eopteranodon and Aurorazhdarcho.

FIgure 1. Reconstruction of MB.R.3531, nesting with Eoazhdarcho, Eopteranodon and Aurorazhdarcho.

But phylogeny is not what interests Habib and Pittman.
They report, “We provide the description of an exceptionally well-preserved specimen of a juvenile aurorazhdarchid from the Jurassic of Germany which preserves details of the wing membrane and pedal webbing and use it to address mechanical questions regarding launch from water in small pterosaurs.” We can’t be sure it’s a juvenile because pterosaur juveniles are isometric copies of their parents and phylogenetic miniaturization often attends the genesis of new pterosaur clades.

This is a wading pterosaur, part of a clade of long-legged wading pterosaurs. It has webbed feet for wading, not for swimming. Wading birds don’t go in water deeper than they can wade in and they take to the air by flapping their wings and leaping. The MB.R. specimen was originally mistaken for Pterodactylus because it greatly resembled Pterodactylus, another clade of small to medium-sized waders leaving numerous webbed tracks. Also back then they had fewer pterosaurs to compare, other than Pterodactylus.

Habib and Pittman don’t buy into the lepidosaur origin of pterosaurs.
They report, “The latest range of motion estimates for the pterosaur hind limb (Manafzadeh and Padian, 2018) suggest that the hind limbs in pterosaurs had more limited abduction than previously modeled and that the hindlimbs operated primarily in a vertical plane.” We invalidated that claim earlier using phylogeny (pterosaurs are more closely related to squamates than to birds). Dozens of pterosaur fossils show the hind limbs spread and form horizontal stabilizers during flight (Fig. 3). That’s when the webbed feet become useful, as twin vertical stabilizers. Webbed feet are primitive for pterosaurs and are found in pterosaur outgroups, like Sharovipteryx.

Figure 3. Click to animate. The Vienna specimen of Pterodactylus (wings folded). Animation opens the wings and legs to reveal the true shape of pterosaur wings, stretched between the elbow and wingtip with a short fuselage fillet extending from elbow to mid femur. The feet act like vertical stabilizers.

Habib and Pittman insist
“We estimate that MB.R.3531 was capable of taking off from the water surface with a single escape push (under the most liberal model values) or with 1-2 follow-up bounding phases (under the most conservative model values), with the majority of the takeoff energy expended on the initial escape phase. The added propulsive area of the pedal webbing had a notable effect on the overall launch performance, increasing estimated propulsive accelerations by over 20% and reducing the number of required propulsive bounding phases.” There’s no need for bounding for floating pterosaurs. They can simply stretch out and flap their wings like pelicans do (Fig. 4) while they frantically kick their feet. In any case, the MB.R. specimen is a wader, so the problem is moot. We looked at water-launch problems in pterosaurs earlier here, here and here.

Pelican take-off sequence from water.

Figure 4. Pelican take-off sequence from water. Click to enlarge.

Habib and Pittman conclude:
“The exact values and kinematic results should be taken with caution, given the large number of values that had to be broadly estimated or assumed.” One wonders why these authors don’t just let their hypothesis drop in favor of one that employs the more than adequate thrust generating power of pterosaur wings together with frantically paddling feet.

References
Bennett C 2013. New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift, 87, 269–289.
Habib M. and Cunningham J 2010. Capacity for Water Launch in Anhanguera and Quetzalcoatlus. Acta Geoscientica Sinica, 31, Supp.1, 24–25.
Habib M and Pittman M 2018. An “old” specimen of Aurorazhdarcho micronyx with exceptional preservation and implications for the mechanical function of webbed
feet in pterosaurs. Flugsaurier 2018: The 6th International Symposium on Pterosaurs. Los Angeles, USA. Abstracts: 41–43.
Manafzadeh AR and Padian K 2018. ROM mapping of ligamentous constraints on avian hip mobility: implications for extinct ornithodirans. Proceedings of the Royal Society B, 285(1879).

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

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

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.