Pterosaur wing appearance when quadrupedal

Figure 1. GIF animation (2 frames) showing the original and repaired versions of this Quetzalcoatlus statue and its artisans.

Figure 1. GIF animation (2 frames) showing the original and repaired versions of this Quetzalcoatlus statue and its artisans. Pterosaur wings folded to near invisibility when folded as shown by manipulating bones and observing fossils. Only a narrow chord wing membrane, as in figure 2, works here. Note the unwarranted wrinkles in the original wing membrane. Note in the original the trailing edge of the wing membrane is directed to mid-metacarpal, rather than to the 180º metacarpophalangeal joint as in the repaired version, fossils and other illustrations below. And what is going on with those tiny anterior pteroids? That is wrong, so wrong.

Pterosaur workers
artists and filmmakers have struggled to portray pterosaur wing membrane when the wings are folded and the pterosaur is walking around (Figs. 1, 3–5). Fossils (Fig. 2) that show how the wings looked when folded are too often ignored.

Figure 4. Here's how the wing membrane in pterosaurs virtually disappeared when folded. This is CM 11426 (no. 44 in the Wellnhofer 1970 catalog),

Figure 2. Here’s how the wing membrane in pterosaurs virtually disappeared when folded. This is CM 11426 (no. 44 in the Wellnhofer 1970 catalog), Note: the left wing has been axially rotated during taphoonmy such that the folded portion of the membrane was fossilized posterior to the bony spar.

CM11426
(Fig. 2) shows how wing membranes fold down whenever the wing bones are flexed (folded). Like bats, pterosaur wing membranes fold away to near invisibility. If you think CM11426 looks a bit like Quetzalcoatlus, you’re right! It’s in the lineage in the large pterosaur tree (LPT), but it’s not larger than a typical Pterodactylus (Fig. 9).

Stan Winston Pteranodon suit for Jurassic Park 3.

Figure 3. Stan Winston Pteranodon suit for Jurassic Park 3. Those wrinkled wing membranes are a dead giveaway that Winston was lost when it came to wing folding in Pteranodon. And that’s not to mention the too short metacarpals (see fig. 4 for comparison)

For Jurassic Park 3
Stan Winston’s Pteranodon (Fig. 3) had saggy, baggy wing membranes. So did early paintings by Burian (Fig. 4). These clearly do not reflect what happens in fossils and in life.

Figure 4. Artist Z. Burian also struggled to realistically portray the folded wing membrane in pterosaurs forgetting the fossils and the fact that both birds and bats have no trouble folding their wings without wrinkling them.

Figure 4. Artist Z. Burian also struggled to realistically portray the folded wing membrane in pterosaurs forgetting the fossils and the fact that both birds and bats have no trouble folding their wings without wrinkling them.

Too often 
artists freehand their pterosaurs (Fig 5 purple), ignoring the bone and soft tissue evidence.

wo of the most completely known Pteranodon

Figure 4. Two of the most completely known Pteranodon (UALVP24238 and NMC4138) along with the skull of KUVP2212 to scale. In purple, John Conway’s Pteranodon (purple) with a much smaller skull and an inappropriate  elbow-high walking configuration.

Toy Pteranodon, ca. 1962, from the Marx Company.

Figure 5. Toy Pteranodon, ca. 1962, from the Marx Company.

Toy pterosaurs
also suffer from deep chord wing membranes (Fig. 5). Proportions here are wildly inaccurate for the toddler set. Accuracy is also absent in many professional reconstructions that include skeletons (Fig. 4), so there is enough blame to go around. The fossils (Fig. 6) document how the artists and sculptors should present those folded wing membranes. Too few artists and sculptors who claim accuracy are actually producing accuracy.

Figure 1. Click to enlarge. The plate and counter plate of the BSP AS V 29a/b specimen of Pterodactylus with color overlays of the bones and visible soft tissues.

Figure 6. The plate and counter plate of the BSP AS V 29a/b specimen of Pterodactylus with color overlays of the bones and visible soft tissues.

What do you get when you choose accuracy?
A much less monstrous awkward portrayal and a much more elegant bird-like/bat-like portrayal comes from keeping true to the bones and soft tissues as they are. Deep chord wing membranes that attach to pterosaur ankles are as outdated as tail-dragging dinosaur portrayals. And while we’re at it, keep those pteroids pointing inward, forming straight leading edges for the distal propatagia.

Pterodactylus walking. Note the foot will never plant itself in front of the hand here. And why are both hands on the ground at the same time as the back foot? Hmm.

Figure 7. Pterodactylus walking. Note the foot will never plant itself in front of the hand here. And why are both hands on the ground at the same time as the back foot? Hmm.

Pterodactylus walk matched to tracks according to Peters

Figure 8. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

This animation frame (Fig. 7) from a walking pterosaur movie associated with the Crayssac tracks accurately portrays the wing membrane essentially invisible when folded. Artist unknown.

Another animation matched to Crayssac tracks (Fig. 8) does not include wing membranes, but they would have been nearly invisible here. This version shows a more upright quadrupedal stance, as if the pterosaur wings were used like ski poles. As noted earlier, this is essentially a bipedal pose, enabling wing opening and flapping without shifting the center of balance.

Go with the evidence, not traditional and sometimes current renderings. Follow the evidence.

The Vienna Pterodactylus.

Figure 9. The Vienna Pterodactylus.  Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. That is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

While we’re talking about Quetzalcoatlus
and its flying abilities, it is worthwhile to take another look at gracile m4.2 (second wing phalanx) on the giant Q. northropi vs. the same phalanx on the much smaller and more likely volant Q. species (Fig. 10). Sorry I didn’t bring this up during the earlier discussion, on azhdarchid flight, first published online three years ago here, but I forgot I had it, and it’s more damning evidence against giant pterosaur flight.

Figure 1 Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn't make sense if Q. northropi was volant.

Figure 10. Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn’t make sense if Q. northropi was volant.

Figure 1. Freehand wing planform cartoon for Quetzalcoatlus from Witton and Habib 2010. There is no evidence in any pterosaur for this wing plan.

Figure 11. Freehand wing planform cartoon for Quetzalcoatlus from Witton and Habib 2010. There is no evidence in any pterosaur for this wing plan. Such deep chord wings cannot help but create unwarranted wrinkles when folded.

Wing folding
and the muscles that enabled complete flexion (Fig. 12) were covered earlier here.

Figure 1. Pterosaur (Santanadactylus) wing folding. Note when the wing is perpendicular to the metacarpus the flexor must be off axis in order to complete the wing folding process. The insertion must be distal to the joint because the flexor process of m4.1 extends dorsally over the metacarpus during wing folding. Otherwise the ventral (palmar) flexor would be cut off from the swinging dorsal process.

Figure 12. Pterosaur (Santanadactylus) wing folding. Note when the wing is perpendicular to the metacarpus the flexor must be off axis in order to complete the wing folding process. The insertion must be distal to the joint because the flexor process of m4.1 extends dorsally over the metacarpus during wing folding. Otherwise the ventral (palmar) flexor would be cut off from the swinging dorsal process.

References
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. PlosOne 5(11): e13982. doi:10.1371/journal.pone.0013982

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SVP 2 – more Quetzalcoatlus post-cranial studies

Padian et al. 2015
describe the post-crania of Quetzalcoatlus (Fig. 1). There are a few confusing comments in this abstract (see below), which I did not edit. I encourage you to translate them yourself as best as you can.

Quetzalcoatlus in dorsal view, flight configuration.

Figure 1. Quetzalcoatlus in dorsal view, flight configuration.

From the abstract
Quetzalcoatlus northropi was named on the basis of a few incomplete post-cranial
bones that suggested a wingspan of 11-13 m; a morph about half this size is represented by numerous bones and partial skeletons, on which most anatomical studies are based. The 9th and 8th cervical vertebrae could pitch dorsally and the 7th pitched ventrally; the 6th and anterior cervicals pitched dorsally. This bend mitigated horizontal compressive load of the neck on the dorsal column. Some lateral movement was possible at all cervical joints. Dorsal movement was restricted to only three or four mid-dorsals and was mainly lateral. The scapulocoracoid could be protracted and retracted in an arc of about 25°, allowing the glenoid to move anterodorsally and posteroventrally. The humerus could have rotated in the glenoid about 25°; elevated about 45°, and depressed about 25-35°. When soaring, the distal humerus would have been about 20° above the horizontal, and the distal radius and ulna about 15° below it. The angle at the elbow in dorsal view would
have been about 115°. The humerus could move no more than 3-5° anterior to the shoulder, at which point vertical mobility is limited to about 5° above the horizontal and about 10° below it. When the humerus is fully pronated, protraction-retraction is limited to 40-45°. Oriented approximately laterally, the humerus could be elevated above the horizontal about 35°. The radius and ulna could flex to about 75° at the elbow but no rotation [pronation/supination] was possible at either end. When flexed, the radius slid distally over the ulna and retracted the wrist and outboard bones up to 60° (depending on the humeral position). Very limited rotation of the wing metacarpal against the distal syncarpal was possible. The asymmetrical distal ‘pulley’ joint of the wing metacarpal depressed the wing-finger during retraction. All joints of the hind limb are hinges except the hip, a ball-and-socket offset by a neck oriented dorsally, medially, and posteriorly. The hind limb was positioned in walking as in other ornithodirans*, and whether it could be elevated and retracted into a batlike pose incorporated into a hypothetical uropatagium is questionable.”

*a diphyletic taxon.

This abstract feels like
an engineer, in this case, probably J. Cunningham, wrote it, which is good. The reconstruction at reptileevolution.com (Fig. 1) agrees with this description, including the elevation of the elbows in flight, which is rarely done in illustrations and models. There is no trouble elevating the hind limbs into the plane of the wing with those ball and socket joints at the acetabulum. Quetzalcoatlus is often compared to a small airplane in size. Like all pterosaurs it would have also flown like a small airplane, with horizontal stabilizers.

Do not follow the reconstructions of some workers
who overextend the elbows and wrists.

References
Padian K, Cunningham JR and Langston WA (RIP) 2015. Post-cranial functional morphology of Quetzalcoatlus (Pterosauria: Azhdarchoidea) Journal of Vertebrate Paleontology abstracts.

 

Pterodactyls Alive! 1984 BBC video with David Attenborough on YouTube

Pterodactyls Alive! on YouTube click here

It’s more than 30 years old.
It’s not HD. It still supports the notion of a inverted hanging pterosaur. It precedes the discovery of eggs. Even so, it features a gliding Pteranodon model, lots of great sea bird scenes (including diving pelicans, soaring, dipping frigate birds and skimming skimmers) along with several great bat scenes (including grounded bats taking off).

And Mr. Attenborough was just starting to get gray hair back then.  :  )

The video also stars a bipedal animated Dimorphodon following the then recent release of Padian’s early work on that pterosaur.

 

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

Another bad Quetzalcoatlus on YouTube

This YouTube video probably goes back a few years because Alan Turner looks quite young and the dear departed Larry Martin looks quite healthy.

Figure 1. Bad Quetzalcoatlus folds its wings transversely instead of posteriorly -- among many other faults.

Figure 1. Bad Quetzalcoatlus folds its wings transversely instead of posteriorly — among many other faults. Click to play video. Computer animators — please check online for your data! Don’t use Marx toys (Fig. 3)!

 

Figure 1. Quetzalcoatlus specimens to scale.

Figure 2. Quetzalcoatlus specimens to scale. It stood more like a giant stork. And the wings folded up posteriorly, essentially hiding the wing membrane.

 

Toy Pteranodon, ca. 1962, from the Marx Company.

Figure 3. Toy Pteranodon, ca. 1962, from the Marx Company.

Here’s the Marx toy Pteranodon (Fig. 3) that apparently served as the model for the documentary Quetzalcoatlus.

Pterosaurs have been maligned too often, and too often by experts. Let’s hope such foolishness stops sooner, rather than later.

 

Evidence for a flightless Quetzalcoatlus northropi

Quetzalcoatlus northropi (Fig. 1, Lawson 1975) is well known as the largest pterosaur of all time. It is known chiefly from most of the wing, which dwarves that of the more complete specimen of Q. sp. (Kellner and Langston 1996), which was found a mere 40km away from sediments of a similar age (Latest Cretaceous). Other giant azhdarchid pterosaurs competing for “the largest pterosaur of all time” are known from less complete remains.

Figure 1. Quetzalcoatlus specimens to scale.

Figure 1. Click to enlarge. Quetzalcoatlus specimens to scale. Here Q. northropi is 2.5x taller than Q. sp, if nothing else changed other than size. 

Some workers (Henderson 2010) have questioned the flying abilities of Q. northropi. Others (Witton and Habib 2010) have given it tremendous flying abilities, able to soar between continents. Both have relied on scaling the small specimen up to the size of the giant.

I was curious
to compare the large and small specimens. Several years ago I took photos of the large specimen wing at the Langston lab in Austin, Texas. The tracings of the large specimen were scaled down to the size of the small specimen (Fig. 2). They are — almost  — identical.

Figure 1 Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn't make sense if Q. northropi was volant.

Figure 2. Quetzalcoatlus sp. compared to the large specimen wing, here reduced to match that of the smaller specimen. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. Note m4.2 is narrower and shorter on the larger specimen, which doesn’t make sense if Q. northropi was volant. It might have been shorter still if Option 1 is valid. At this point, either is possible. 

Scaling pterosaurs helps one understand some of the “big” questions. Everyone knows that to double the height of the animals is to cube its weight. The same holds true for pterosaurs. So then we might ask, if the larger specimen had higher wing loading, why wasn’t the wing spar more robust? As you can see, the wing elements were not more robust in the giant — AND — m4.2 was more gracile (Fig. 2).

The answer to that question is not so obvious, as we learned before. The proportions of giant azhdarchids were quite similar to those of the tiniest proto-azhdarchids, as you can see below (Fig. 3).

We also see distal wing phalanx reduction in the evolution of the flightless pterosaur, Sos 2428 from tiny ancestors, n42, and n44 (from the Wellnhofer 1970 catalog, Fig. 3) with longer wings.

Figure 2. The flightless pterosaur, Sos 2428, along with two ancestral taxa, both fully volant. Note the reduction of the wing AND the expansion of the torso. We don't know the torso of Q. northropi. It could be small or it could be very large.

Figure 3. The flightless pterosaur, Sos 2428 to scale along with two ancestral taxa, both fully volant. Note the reduction of the wing AND the expansion of the torso. We don’t know the torso of Q. northropi. It could be small or it could be very large.

Here in the flightless pterosaur (Fig. 3), perhaps more importantly, the torso expanded greatly in every direction during the evolution of flightlessness. The pelvis was also much larger in Sos 2428.

We don’t have enough torso material from the Quetzalcoatlus northropi specimen to understand its volume. While it is possible that the torso remained small, as in Q. sp. (Fig. 1), it is equally possible that it could have expanded to become voluminous, as in Sos 2428.

Until we know, we can only guess, but the relative reduction of the distal wing elements, beyond what we see in the smaller specimen, adds weight to the argument that flight was more difficult for the giant.

More data would help settle this issue.
We take our clues wherever we can. Don’t overlook the little stuff.

References
Henderson DM (2010). Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30(3):768-785.
Kellner AWA and Langston W 1996. Cranial remains of Quetzalcoatlus (Pterosauria, Azhdarchidae) from late Cretaceous sediments of Big Bend National Park, Texas. – Journal of Vertebrate Paleontology 16: 222–231.
Lawson DA 1975. Pterosaur from the latest Cretaceous of West Texas: discovery of the largest flying creature. Science 187: 947-948.
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. PlosOne 5(11): e13982. doi:10.1371/journal.pone.0013982

wiki/Quetzalcoatlus

 

 

Digital modeling of pterosaurs (Henderson 2010)

Yesterday, and the day before, we reviewed Hone and Henderson (2013) who conducted computational experiments with four misbegotten digital pterosaur models (Fig. 1). They reported that pterosaurs were unlikely floaters that would have struggled to keep their noses above the surface and so risked drowning, despite their air-filled skeletons.

Jurassic Park 3 logo, including a nice Pteranodon in ventral view with narrow chord wings.

After seeing Jurassic Park I, II and III, many readers may think that digital modeling with computers has already reached some sort of acme, able to accurately model these reptiles with ultra-precision. Unfortunately, when it comes to academic publication, that’s not always the case. And yet such works as Hone, Sullivan and Bennett (2009), Henderson (2010) and Hone and Henderson (2013) continue to be published.

Bring up the quality please
I have no beef with digital models, but the quality has to be there. The last time I saw Hone present a digital model it was for a sabertooth paw built with digital cylinders designed to discredit PILs (Hone, Sullivan and Bennett 2009, Fig. 1). These cylinders did not echo the real bone configurations. Taking up this challenge (Peters 2010) used a real sabertooth paw (Fig. 1) and found PILs, as anyone can.

Figure 1. Above: A digital Smilodon pes created by Hone, Sullivan and Bennett. This is a poor substitute for a tracing of the real Smilodon manus and pes, with naturally flexed and extended phalanges and complete PILs added. Lesson: try to avoid digital models until the accuracy rises to the occasion.

Figure 1. Above: A digital Smilodon pes created by Hone, Sullivan and Bennett.
This is a poor substitute for a tracing of the real Smilodon manus and pes, with naturally flexed and extended phalanges and complete PILs added. Lesson: try to avoid digital models until the accuracy rises to the occasion. Due to these flexions and extensions, cat paws are more of a 3D problem in PILs, rather than the more typical planar configuration.

In similar fashion,
Henderson’s (2010) digital model of Quetzalcoatlus (Fig. 3) has been wisely criticized as also being inaccurate*. It’s as if he did not pay any attention to the bones and soft tissues preserved and the implications those have for muscle masses, especially those of the hind limb. In other words, Henderson seems to have skipped a very important step: start with the bones and create an accurate reconstruction on paper before going digital. The same holds true for his Rhamphorhynchus (Fig. 2).

Figure 2. Henderson (2010) modeled Rhamphorhynchus with a deep chord wing, tiny thighs and shallow pelvic area and an inflexible neck, all inaccurate based on reconstructing the bones.

Figure 2. Henderson (2010, above left) modeled Rhamphorhynchus with a deep chord wing, tiny thighs and shallow pelvic area and an inflexible neck, all inaccurate based on reconstructing the bones (lower and at right). Perhaps of more importance to the floating argument, the phalanges are too slender in the Henderson model, so yes, they would make less efficient pontoons in that model.

 

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 3. Quetzalcoatlus recreated as a digital model by Henderson 2010 compared to a bone reconstruction. No wonder the results were odd. The geometry and the math had no chance of being correct with such a wrong reconstruction.

I have no trouble with those who make 3D reconstuctions digitally. I think that’s the wave of the future. I do have a problem with those who claim they are accurate when they are not. And likewise I have a problem with referees and colleagues who give a green light to these little monsters, permitting these pterosaur experts to disfigure pterosaurs.

* from Wikipedia/Quetzalcoatlus: “Henderson’s work was further criticized by Habib, who pointed out that although Henderson used excellent mass estimations, they were based on outdated pterosaur models,”

References
Henderson, DM.  2010. Pterosaur body mass estimates from three-dimensional mathematical slicing, Journal of Vertebrate Paleontology, 30(3):768-785.
Hone DWE, Sullivan C, Bennett SC 2009. Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions.Historical Biology (Impact Factor: 1.19). 03/2009; 21:67-77. DOI:10.1080/08912960903154503
Hone DWE, Henderson DM 2013. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats, Palaeogeography, Palaeoclimatology, Palaeoecology (2013 accepted manuscript), doi: 10.1016/j.palaeo.2013.11.022
Peters, D. 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500