Scaphognathus wing membrane in visible light

Today a paper by Jäger et al. 1831
put the holotype of Scaphognathus (Goldfuß 1831; Late Jurassic) under various forms of illumination and re-discovered soft tissue originally noted and rarely cited.

Figure 1. Holotype of Scaphognathus GIF animation showing extent of wing membrane ignored by xx et al. 2018.

Figure 1. Holotype of Scaphognathus GIF animation showing extent of wing membrane ignored by xx et al. 2018.

Ironically
the authors ignored the most obvious aspect of the Scaphognathus soft tissue: the presence of a narrow chord wing membrane (Fig. 1), as documented by Peters (2002) and ignored ever since, per Chris Bennett’s threat, “You won’t get published, and if you do get published, you won’t get cited.”

Figure 2. Here is the Vienna specimen of Pterodactylus in situ and with matrix removed. Now compare this figure with figure 3, which shows the wings and uropatagia unfolding. There is no way to turn this into a deep chord wing membrane. And it decouples the forelimbs from the hind limbs.

Figure 2. Here is the Vienna specimen of Pterodactylus in situ and with matrix removed. Now compare this figure with figure 3, which shows the wings and uropatagia unfolding. There is no way to turn this into a deep chord wing membrane. And it decouples the forelimbs from the hind limbs.

The Vienna specimen of Pterodactylus
(Figs. 2, 3) are the prime examples of a narrow chord wing membrane, stretched between the wing tip and elbow… as in all pterosaurs that preserve soft tissue.

The Vienna Pterodactylus.

Figure 3. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. There is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

There are still no examples
of a deep chord wing membrane (attached to the ankle or tibia) preserved in any pterosaurs, as documented here, here, here and here.

References
Goldfuß A 1831. Beiträge zur Kenntnis verschiedener Reptilien der Vorwelt. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum, 15:61-128.
KRK Jäger, Tischlinger H, Oleschinski G, and Sander PM 2018. Goldfuß was right: Soft part preservation in the Late Jurassic pterosaur Scaphognathus crassirostris revealed by reflectance transformation imaging (RTI) and UV light and the auspicious beginnings of paleo-art. Palaeontologia Electronica 21.3.4T: 1-20. pdf
Peters D 2002. A new model for the evolution of the pterosaur wing – with a twist. Historical Biology 15: 277–301.

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Is Jeholopterus pregnant? And what’s hiding in plain sight beneath that left wing?

There seems to be an overlooked egg shape
inside Jeholopterus, the vampire pterosaur, at just the right place (Figs. 1, 2; IVPP V12705). It’s not full term, so embryo/hatchling bones are not readily visible (= fully ossified) and currently impossible to reconstruct. Then again, that patch could be just a scuff mark.

Figure 1. Jeholopterus GIF animation showing new left wing shape plus underlying debris, perhaps in the form of theropod feathers.

Figure 1. Jeholopterus GIF animation showing new left wing shape plus underlying debris, some in the form of theropod feathers. Folded wings on pterosaurs should essentially disappear. This new interpretation follows that hypothesis. Click for an enlarged image.

Remember
pterosaurs are fenestrasaur – tritosaurlepidosaurs, so they are able to retain eggs within the mother’s body until just before hatching. Even their super-thin, lizard-like egg shells (or lack thereof) supports the present tree topology of pterosaurs as lepidosaurs in the large reptile tree (LRT, 1315 taxa) and disputes traditional models of archosaurian origin first invalidated by Peters 2000 by phylogenetic testing. Pterosaur eggs found alone (not near the mother) outside the body (like the IVPP anurognathid) include full term embryos. The Hamipterus egg accumulation chronicles a mass death of pregnant mothers, probably by lake burping.

Moreover
Jeholopterus seems to have landed on (= sunk on to after death) some theropod/bird feathers or similarly shaped pond plants. I suspected there was something wrong with that way-too-broad-while-folded wing. Pterosaur wings typically fold up to near nothingness, like bat wings do, when folded. It turns out, that’s the case here, too. There is a fringed trailing edge where the current and correct blue area ends. Make sure you click for a larger image.

Figure 2. Possible Jeholopterus premature egg in which embryo bones are not well calcified. Ribs and gastralia on a separate frame.

Figure 2. Possible Jeholopterus premature egg in which embryo bones are not well calcified. Ribs and gastralia on separate frames.

Look up at the left hand
of Jeholopterus and you’ll see there is some sort of fossilized matter (greenish color added on overlay) on the stratum that the specimen sank to. The same appears to be happening near the left wing tip, where something like feathers or long leaves appear, giving the illusion of a little too much pterosaur wing chord, especially in comparison to the right wing, which appears ‘normal.’

Figure 3. Jeholopterus counter plate in UV with brachiopatagium traced.

Figure 3. Jeholopterus counter plate in UV with brachiopatagium traced. UV image from Kellner et al. 2010.

Jeholopterus ninchengensis (Wang, Zhou, Zhang and Xu 2002) Middle to Late Jurassic, ~ 160 mya, [IVPP V 12705] was exquisitely preserved with wing membranes and pycnofibers on a complete and articulated skeleton (see below). Unfortunately the fragile and crushed skull was undecipherable to those who observed it first hand. Using methods described here, Peters (2003) deciphered the skull and identified the IVPP specimen of Jeholopterus as a vampire. In that hypothesis, Jeholopterus stabbed dinosaurs with its fangs, then drank their blood by squeezing the wound with its plier-like jaws while hanging on with its robust limbs and surgically sharp, curved and elongated claws. From head to toe, Jeholopterus stood apart morphologically. It was not your typical anurognathid. Derived from a sister to the CAGS specimen attributed to Jeholopterus, the holotype of Jeholopterus was a phylogenetic sister to Batrachognathus.

Figure 2. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer.

Figure 4. Reconstruction of Jeholopterus. This owl-like bloodslurper was covered with super soft pycnofibers to make it a silent flyer. Note the wider than tall torso and super long, super sharp claws.

These Jeholopterus wing images support
the narrow chord wing membrane stretched between elbow and wing tip (Peters 2002) and ignored by all subsequent workers. Note: Peters 2002 did not understand that something else made the left wing of Jeholopterus appear to have a deeper chord at mid wing. The illusion is that complete!

References
Cheng X, Wang X, Jiang S and Kellner AWA 2014. Short note on a non-pterodactyloid pterosaur from Upper Jurassic deposits of Inner Mongolia, China. Historical Biology (advance online publication) DOI:10.1080/08912963.2014.974038
Kellner AWA, Wang X, Tischlinger H, Campos DA, Hone DWE and Meng X 2010. The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane. Proc Royal Soc B 277: 321–329.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2003. The Chinese vampire and other overlooked pterosaur ptreasures. Journal of Vertebrate Paleontology 23(3): 87A.
Wang X, Zhou Z, Zhang F and Xu X 2002. A nearly completely articulated rhamphorhynchoid pterosaur with exceptionally well-preserved wing membranes and “hairs” from Inner Mongolia, northeast China. Chinese Science Bulletin 47(3): 226-230.

wiki/Jeholopterus

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.

Big pterosaurs: big or little wing tips

Earlier and below (Fig. 2) we looked at large and giant pterosaur wings comparing them to the largest flying birds, including one of the largest extant flying birds, the stork, Ciconia, and the extinct sheerwater, Pelagornis, the largest bird that ever flew.

FIgure 2. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus

FIgure 1. A basal pteranodotid, the most complete Pteranodon, the largest Pteranodon skull matched to the largest Pteranodon post-crania compared to the stork Ciconia and the most complete and the largest Quetzalcoatlus. Note the much reduced distal phalanges in the complete and giant Quetzalcoatlus, distinct from the Pteranodon species.

Today
we’ll look at how the largest Pteranodon (Figs. 1, 4) compares to much larger pterosaurs, like Quetzalcoatlus northropi (Figs. 1, 2) that have vestigial wingtips similar to those of the  much smaller flightless pre-azhdarchid, SOS 2428 (Fig. 3).

Note the tiny three distal phalanges
on the wing of the largest Quetzalcoatlus, distinct from the more typical elongate and robust distal phalangeal proportions on volant pterosaurs of all sizes. Much smaller definitely flightless pterosaurs, like SOS 2428, shrink those distal phalanges, too. That’s the pattern when pterosaurs lose the ability to fly.

Figure 2. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.

Figure 2. A previously published GIF animation. Q. northropi and Q. sp. compared to Ciconia, the stork, and Pelagornis, the extinct gannet, to scale. That long neck and large skull of Quetzalcoatlus would appear to make it top heavy relative to the volant stork, despite the longer wingspan. Pteranodon and other flying pterosaurs do not have such a large skull at the end of such a long neck (Fig. 1). The longer wings of pelagornis show what is typical for a giant volant tetrapod, and Q. sp. comes up short in comparison.Today we’ll compare the wingspan of the largest Quetzalcoatlus to the largest and more typical Pteranodon species (Fig. 2).

Unfortunately
pterosaur workers refuse to consider taxa known to be flightless, like SOS 2428 (Peters 2018). It’s easy to see why they would be flightless (Fig. 3). Scaled to similar snout/vent lengths with a fully volant pterosaur like n42 (BSPG 1911 I 31) the wing length and chord are both much smaller in the flightless form.

Lateral, ventral and dorsal views of SoS 2428

Figure 3. Lateral, ventral and dorsal views of the flightless SoS 2428 (Peters 2018) alongside No. 42, a volant sister taxon.

Comparing the largest ornithocheirid,
SMNK PAL 1136, to the largest Pteranodon (chimaera of largest skull with largest post-crania in Fig. 4) shows that large flyers have elongate distal phalanges, distinct from body and wing proportions documented in the largest azhdarchids, like Quetzalcoatlus.

Figure 5. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136.

Figure 4. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136. Note the long distant wing phalanges on both of these giant flyers. This is what pterosaurs evolve to if they want to continue flying. And this is how big they can get and still fly. Giant azhdarchids exceed all the parameters without having elongate wings. Note: the one on the left has a longer wingspan whir the one on the right has a more massive torso and skull together with more massive proximal wing bones and pectoral girdle. On both the free fingers are tiny, parallel oriented laterally and slightly tucked beneath the big knuckle of the wing finger. The pteroid points directly at the deltopectoral crest. 

As the largest Pteranodon and largest ornithocheirid (SMNS PAL 1136)
(Fig. 4) demonstrate, as flying pterosaurs get larger, they retain elongate distal wing phalanges. And big, robust phalanges they are.

By contrast in azhdarchids and pre-azhdarchids
there is a large size bump after n42 (BSPG 1911 I 31) the fourth wing phalanx either disappears (see Microtuban and Jidapterus) or shrinks to a vestige. Then there’s Zhejiangopterus (Fig. 5), with a big pelvis, gracile forelimbs and a giant skull on a very long neck. Just that neck alone creates such a long lever arm that the pterosaur is incapable of maintaining a center of balance over or near the shoulder joints.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 5. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

As mentioned earlier, becoming flightless permitted, nay, freed azhdarchid pterosaurs to attain great size. They no longer had to maintain proportions that were flightworthy. Instead they used their shortened strut-like forelimbs to maintain a stable platform in deeper waters. And when they had to move in a hurry, their wings could still provide a tremendous amount of flurry and thrust (Fig. 6) for a speedy getaway.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 6. Quetzalcoatlus running without taking off, using all four limbs for thrust. That long lever arm extending to the snout tip in front of the center of gravity is not balanced in back of what would be the center of lift over the wings

For the nitpickers out there…
some specimens of Nyctosaurus (UNSM 93000, Fig. 7) also have but three wing phalanges, but they are all robust. The distal one is likely the fourth one because it remains curved. Phalanges 2 and 3 appear to have merged, or one of those was lost. Compare that specimen to a more primitive Nyctosaurus FHSM VP 2148 with four robust wing phalanges.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

Figure 5. Cast of the UNSM 93000 specimen of Nyctosaurus. Missing parts are modeled here.

References
Peters D 2018. First flightless pterosaur (not peer-reviewed). PDF online.

 

Largest ‘flying reptile’ from the Crato formation? Maybe not.

Cheng et al. 2018
report on a partial wing finger (MPSC R 1221, Fig. 1) that they say represents, “The largest flying reptile from the Crato Formation, Lower Cretaceous, Brazil.”

But is it? 

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

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

No…
if the scale bars are correct. The larger, as yet undescribed, and very impressive SMNS PAL 1136 specimen (Fig. 1) is not mentioned in the text. I do not know if the SMNS specimen is from the Crato or Roualdo formation (I have not gone back to look up that datum). In any case, the authors overlooked this specimen, because it is not mentioned in the text or charts that list a few dozen other large pterosaurs. It should have been included. Of course, then the headline would have read, “…second largest…” and no one wants that.

So was this oversight intentional?
We’ll never know. The SMNS specimen has been in the literature for 24 years (Frey and Martill 1994).

Addendum several days later
The Crato Formation was not erected until 13 years after the 1994 paper by Martill, Bechly and Loveridge. Therefore all layers were considered Santana Formation in 1994. So the SMNS specimen from the Santana formation might have come from the upper or lower layers. It should have been included in the 2018 survey.

The authors conclude
“Based on the fusion of the extensor tendon process and the first wing phalanx and bone histology, MPSC R 1221 presents a subadult individual of a late ontogeny stage (OS5) at time of death, whichmeans that the final maximized wingspan might have been larger. This is corroborated by the osteohistological sections since this individual did not present an external fundamental system.” Look how eager the authors are to hang on to that superlative, ‘largest’, even though we know of at least one that is so much larger.

The authors do not realize
or continue to deny data, that pterosaurs do not follow archosaur fusion patterns during ontogeny—because pterosaurs are not archosaurs, and their fusion patterns follow phylogenetic patterns.

I never heard the term,
“external fundamental system” before. So, I looked it up: “A closely spaced series of lines of arrested growth that is called the External Fundamental System (EFS) indicates that adult size has been reached.” Now we all know!

I hope this blog post
will one day turn out dozens of young paleontologists who will read every paper they see with a seasoned and skeptical eye. If so, a few of you may someday become editors of academic journals or manuscript referees. When that happens, don’t let mistakes like this slip out. Having a website, like ReptileEvolution.com, that is full of data and illustrations, makes it easy to fact-check superlative claims, like this one, with just a few clicks.

On that note:
here (Fig. 2) is a published illustration of a pterosaur wrist from Duque and Barret 2018 with labels that were a little mixed up with regard for the ulna and radius. The referees should have caught this.

Figure 1. From figure 9 from Duque and Barreto 2018 with corrections noted and digit 5 colorized

Figure 2. From figure from Duque and Barreto 2018 with corrections noted and digit 5 colorized. This mistake should have been caught by the authors and referees, not me.

References
Cheng X, Bantim RAM, Sayão JM, Kellner AWA, Wang X and Saraiva AAF 2018. The largest flying reptile from the Crato Formation, Lower Cretaceous, Brazil. Historical Biology. https://doi.org/10.1080/08912963.2018.1491567
Duque RRC and Barret AMF 2018. New exceptionally well-preserved Pterosauria from the lower Cretaceous Araripe Basin, Northeast Brazil. Cretaceous Research 10.1016/j.cretres.2018.05.004
Frey E and Martill DM 1994. A new Pterosaur from the Crato Formation (Lower Cretaceous, Aptian) of Brazil. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 194: 379–412.

Battle of the giant Quetzalcoatlus sculptures

Bigger is better
especially when it comes to pterosaurs in museum exhibits. To wit: The Field Museum (Chicago, IL, USA) is installing a flying Quetzalcoatlus (Fig. 3) and a standing Quetzalcoatlus (largely imagined and restored, based on an almost complete wing bone, Fig. 1).

The artist/professors in Southern England
have one as well (Fig. 1). And full scale Q. northropi sculptures can be found worldwide! (See links and images at the end of this post.)

Figure 1. Field Museum Quetzalcoatlus (tan) vs. English Quetzalcoatlus (gray) vs. a tracing of the real Q. sp. and Q. northropi scant remains.

Figure 1. Field Museum Quetzalcoatlus (tan) vs. English Quetzalcoatlus (gray) vs. a tracing of the real Q. sp. and Q. northropi scant remains. Yes, the skull on the Field Musuem model is too long, evidently following the invalid archosaur hypothesis of origin. Pterosaurs, like other tritosaurs, do not change their proportions during growth as fossils demonstrate.

These models arrive on the heels
of a recent post on flightless giant pterosaurs. The Field Museum model (Fig. 1) appears to have a more precisely modeled skull, though about 50% too long (but really, without a skull, who knows?). Perhaps the skull was elongated (based on the smaller ?species) based on the invalid archosaur hypothesis of pterosaur origins. We know from the evidence of fossils that hatchlings and juvenile pterosaurs had adult proportions, not longer skulls.

Both models suffer
from putting too much weight on the tiny free fingers. The feet should be beneath the shoulder joint, as in birds, to take the weight off the tiny hyperextended fingers, acting more like ski poles, not providing thrust, only some sort of support.

The folded wing membrane should tend to disappear
(Fig. 2), but it shows in both models. The wing finger should flex closer to the elbow, but it doesn’t (probably to let the wing membrane show). The wing membrane chord should be shorter, to the elbow, but in both models the brachiopatagium blends with the leg, always awkwardly and in defiance of the data preserved in all pterosaur fossils (Fig. 2) that preserve soft tissue.

Here's how the wing membrane in pterosaurs virtually disappeared when folded.

Figure 2. Here’s how the wing membrane in pterosaurs virtually disappeared when folded. This is a tiny pre-azhdarchid, CM 11426.

Over at the Carnegie Museum (Pittsburgh, PA, USA)
they have a tiny pre-azhdarchid, CM 11426 (Fig. 2), with real wing membranes, as described above, matching those of other pterosaur soft tissues.

Figure 3. Field museum flying Quetzalcoatlus model has the invalid deep chord wing that attaches to the tibia.

Figure 3. Field museum flying Quetzalcoatlus model has the traditional but invalid deep chord wing that attaches to the tibia and makes this sort of pterosaur untenably awkward.

Figure 2. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. No wonder the results were odd. The math was wrong.

Figure 4. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. This is a possible slightly deeper wing chord. Compare this one to figure 5, which is more typical. And look at those hind limbs, like those of Sharovipteryx, forming a horizontal stabilizer, just like a typical airplane. And it matches the evidence (Fig. 2).

Not sure why pterosaur paleontologists
keep insisting that evidence (Fig. 2) can and should be ignored. It’s disheartening to see this and leaves them open to criticism.

Quetzalcoatlus running like a lizard prior to takeoff.

Figure 5. Quetzalcoatlus running like a lizard prior to takeoff. Click to animate. Giant azhdarchids gave up flying by reducing the lenth of their wings, following the patterns of other flightless pterosaurs. There is no awkwardness with this narrow chord wing design, which follows fossils like CM 11426 (Fig. 2).

Other online Quetzalcoatlus models/sculptures:

Low Poly Quetzalcoatlus model

https://www.alamy.com/stock-photo-muenchehagen-germany-10th-apr-2017-a-sculpture-of-the-quetzalcoatlus-138149396.html

https://blog.everythingdinosaur.co.uk/blog/_archives/2014/07/07/collecta-quetzalcoatlus-with-prey-model.html

If some of these seem to defy the ability to fly based on
a too far aft center of lift and a too far forward center of balance, or too small of a wing for such a large mass, no worries mate! If the imagination can soar, then so can these giants (NOT!) In the above YouTube video, the invalid, but traditional batwing shape of the brachiopatagium is best seen in the pterosaur’s shadow.

Quetzalcoatlus northropi

Tierra de dinos - Quetzalcoatlus Northropi

IF the wing membranes seem encumbering
awkward, liable to trip up the pterosaur or catch on some low lying shrub, no worried, mate! As these pterosaurs once wandered, let your imagination wander. There’s no need to precisely follow the evidence (Fig. 2) that shows the wing membranes essentially disappearing while flexed/folded.

Quetzalcoatlus at the Toledo Zoo

It’s going to be difficult to raise the wings for flight
given some of these awkward quadrupedal poses. Much better to have the center of balance over the toes at all static times (see below), shifting the balance forward while running at full speed (Fig. 5), like birds.

http://www.iaapa.org/DigitalShowDaily/2016/wed/Billings.asp

https://hiveminer.com/Tags/quetzalcoatlus

Why is this Houston Museum Quetzalcoatlus posed like this? Very strange.

Why is this Houston Museum Quetzalcoatlus posed like this? Very strange.

Quetzalcoatlus neck poses. Dipping, watching and displaying.

Quetzalcoatlus neck poses from David Peters Studio. Dipping, watching and displaying. Yes, the third finger is wrong here. It should be pointing posteriorly.

With what we know about pterosaurs
this should be a golden age of restoration. Instead, these models will someday be seen for what they are… near misses. They replace elegance with awkwardness, facts with fancy, and precision with tradition.

References
https://blog.everythingdinosaur.co.uk/blog/_archives/2018/06/01/pterosaur-models-go-on-display.html

Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist 
Historical Biology 15: 277-301

Axial rotation: fingers in pterosaurs, toes in birds

A somewhat recent paper by Botelho et al. 2015
looked at the embryological changes that axially rotate metatarsal 1 to produce a backward-pointing, opposable, perching pedal digit 1 (= hallux).

Hallux rotation phylogenetically
Botelho reports: Mesozoic birds closer than Archaeopteryx to modern birds include early short-tailed forms such as the Confuciusornithidae and the toothed Enantiornithes. They present a Mt1 in which the proximal portion is visibly non-twisted, while the distal end is offset (“bent”) producing a unique “j-shaped” morphology. This morphology is arguably an evolutionary intermediate between the straight Mt1 of dinosaurs and the twisted Mt1 of modern birds, and conceivably allowed greater retroversion of Mt1 than Archaeopteryx.”

“D1 in the avian embryo is initially not retroverted9, and therefore becomes opposable during ontogeny, but no embryological descriptions address the shape of Mt1, and no information is available on the mechanisms of retroversion.”

Figure 1. Pes of the most primitive Archaeopteryx, the Thermopolis specimen.

Figure 1. Pes of the most primitive Solnhofen bird, the Thermopolis specimen. This digit 1 never left the substrate.

In Tyrannosaurus,
(Fig. 2) the entire metatarsal 1 with pedal digit 1 is rotated just aft of medial by convergence. It’s not axially rotated. It’s just attached to the palmar side of the pes. This pedal digit 1 was elevated above the substrate.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views.

Figure 2. The semi-retroverted pedal digit 1 of Tyrannosaurus rex in two views. This digit 1 was elevated above the substrate.

In some birds
like the woodpecker, Melanerpes, and the unrelated roadrunner, Geococcyx, pedal digit 4 is also retroverted. Sorry, I digress.

Further digression
The axial rotation of pedal digit 1 in birds is convergent with the axial rotation of metacarpal 4 in Longisquama (Fig. 3) and pterosaurs. In both taxa the manus was elevated off the substrate and permitted to develop in new ways. Manual digit 4 never leaves an impression in pterosaur manus tracks… because it is folded, like a bird wing, against metacarpal 4. In Longisquama such extreme flexion is not yet possible.

Figure 1. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized, as in pterosaurs.

Figure 3. Longisquama left and right manus traced using DGS then reconstructed (below). This is a very large hand for a fenestrasaur and manual digit 4 is oversized and the metacarpal is axially rotated, as in pterosaurs. Manual digit 5 is useless, but not yet a vestige. A pteroid is present, as in Cosesaurus. The coracoid is elongate as in birds. The sternum, interclavicle and clavicle are assembled into a single bone, the sternal complex, as in pterosaurs.

Note the lack of space between
the radius and ulna in Longisquama. This is what also happens in pterosaurs. It prevents the wrist from pronating or supinating, as in birds and bats… which means, the forelimb is flapping, not pressing against the substrate, nor grasping prey. That means all those images of Longsiquama on all fours are bogus. Now you know.

So now we come full circle
While the toes of birds axially rotate and the wing metacarpal of pterosaurs axially rotates, the forearms of birds, pterosaurs and Longisquama do not axially rotate. No one wants their wing to twist.

References
Botelho JF, Smith-Paredes D, Soto-Acuña S, Mpodozis J, Palma V and Vargas AO 2015. Skeletal plasticity in response to embryonic muscular activity underlies the development and evolution of the perching digit of birds. Article in http://www.Nature.com/Scientific Reports · May 2015 DOI: 10.1038/srep09840