Walking azhdarchid movie matched to pterosaur tracks

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

Pterodactylus walk matched to tracks according to Peters

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

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

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

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

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

The troubles with the horizontal backbone model are at least threefold

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

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

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

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

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

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

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

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

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

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

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

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

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

Quetzalcoatlus scraping bottom while standing in shallow water.

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

 

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

wiki/Zhejiangopterus

Dimorphodon pterosaur takeoff – revised

Earlier I produced an animated GIF that showed how Dimorphodon could not have taken off using its forelimbs (Fig. 1; contra Witton 2013). At the same time I produced an animated GIF that showed how Dimorphodon could have taken off using its hind limbs

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

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

with wings still folded (modified Fig. 2), noting that back then I preferred to use the wings, but wanted to show how powerful the hind limbs were. For some reason I waited until today to offer an animated GIF in which the wings open prior to takeoff and together with the hind limbs initiate a power launch with maximum thrust (Fig. 3), just like birds.

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

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

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

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

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

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

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

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

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

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

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

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

Pterosaur launch talk from 2012 on YouTube

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

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

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

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

AMNH animated pterosaur takeoffs

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

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

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

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

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

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

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

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

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

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

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

Quetzalcoatlus running like a lizard prior to takeoff.

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

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

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

Quetzalcoatlus in dorsal view, flight configuration.

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

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

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

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

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

 

Largest flying creature ever video on YouTube

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

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

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

Quetzalcoatlus is featured, of course.

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

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

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

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

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

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

 

 

 

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

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

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

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

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

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

Two unlikely forelimb launching pterosaurs

Today we’ll look at two very different pterosaurs and wonder how it was even possible that these should be considered to be forelimb launchers.

The first is the basal pterosaur, MPUM 6009 (Fig. 1). It has the longest hind limbs compared to fore limbs. In these pterosaurs the hind limb leap alone would obviate the need for further spring off the forelimbs. Moreover, putting the short forelimbs on the substrate demands an awkward butt-high configuration unlikely to provide any sort of efficient launching. Phylogenetically all pterosaurs following this one had longer forelimbs capable of touching the substrate without losing balance over the toes.

MPUM 6009 with red and orange layers applied to show muscles. The hind limbs are well muscled, fully capable of leaping. The forelimbs are incapable of touching the ground without a very awkward butt-high configuration.

Figure 1. MPUM 6009 with red and orange layers applied to show muscles. The hind limbs are well muscled, fully capable of leaping. The forelimbs are incapable of touching the ground without a very awkward butt-high configuration.

Basal pterosaurs, derived from long-legged flapping fenestrasaurs like Longisquama, had longer hind limbs than forelimbs. This legacy of this hind limb leaping cannot be ignored.

 A completely different situation here with Nyctosaurus bonneri, in which the forelimbs are much longer than the hind limbs. Could those forelimb muscles provide a sufficient leap to clear the ground with those giant wing fingers before it comes crashing back to earth. Better to extend the wings while bipedal on those meaty thighs, then start flapping, running and leaping.

Figure 2. A completely different situation here with Nyctosaurus bonneri, in which the forelimbs are much longer than the hind limbs. Could those relatively small forelimb muscles provide a sufficient leap to clear those giant wing fingers before crashing back to earth? Better to extend the wings while bipedal on those meaty thighs, then start flapping, running and leaping, adding thrust with each wing flap.

When the forelimbs are much longer than the hind limbs
Nyctosaurus (Fig. 2) is the prime example of pterosaurs with the opposite morphology: longer forelimbs than hind limbs. Here it is hard to imagine this pterosaur becoming airborne without extending its wings for lift. The meaty thighs could have kept this pterosaur balanced over its toes while the wings unfolded. The meaty thighs could also have provided an initial leap or run to launch. Such large wings would have provided extra thrust, but only while extended. The triceps muscles appear to be pitifully too small to rapidly extend the forelimb to launch the pterosaur like a super pogo-stick.

Most other pterosaurs have a more balanced configuration with forelimbs and hind limbs more closely related in terms of length and the placement of joints. Even these were able to raise their forelimbs off the substrate to unfold the wings without losing balance over the toes.

Causes of the problem
Shortchanging the muscles of the pelvis, prepubis and femur by Witton (2013) and others is only one cause of their false paradigm. Creating poor reconstructions that disfigure real morphology is the second problem. Putting faith in imaginary ancestors with odd and improbable morphologies rather than verifiable fossil ancestors with real bones is the third cause.

That’s why I’m here, to encourage change based on evidence.

Scathing Book Review – Pterosaur hind limb muscles and the prepubis: Witton vs Peters

Earlier here, here and here we had a critical look at the hypotheses regarding various aspects of pterosaur phylogeny and morphology. Today we’ll look at the muscles of the pterosaur hind limb and how Witton (2013) emaciated them.

Pterosaur hind limb muscles according to Witton (2013, above) and based on lizard musculature (Fig. 2).

Figure 1. Pterosaur hind limb muscles according to Witton (2013, above) and based on lizard musculature (Fig. 1, below and Figs. 2, 3). Witton does not extend femoral muscles to the prepubis or the anterior ilium. Evidently it’s important for those who do not want pterosaurs to exhibit any bipedal abilities to denigrate hind limb muscle strength, as shown by the emaciated appearance Witton gives them and by reducing their anchorage.

Make sure those hind limbs look emaciated
if you want to convince others that pterosaur hind limbs were not capable of providing bipedal locomotion (in step with quadrupedal locomotion for most) or hindlimb leaping/launching/takeoff. Witton 2013 emaciates his pterosaur femoral muscles and reduces their points of origin on the ilium and prepubis. Why? He supports the forelimb launch hypothesis for pterosaurs big time.

Two dead lizards, dorsal and ventral views. Note the meaty thighs.

Figure 2. Two dead lizards, dorsal and ventral views. Note the meaty thighs. Same as in birds and crocs. Witton emaciates them.

Real lizard femoral muscles are robust and meaty (Figs. 2,3 ). The muscles get thicker at mid thigh. This even happens in birds and crocs! Why would Witton emaciate them?

Lizard muscles according to Romer (1956. 1062,1971). Ilium muscles in red. Pubis and ischium muscles in blue. Caudal muscles in yellow.

Figure 3. Lizard muscles according to Romer (1956. 1062,1971). Ilium muscles in red. Pubis and ischium muscles in blue. Caudal muscles in yellow. Curious that no muscles arise from the posterior ilium.

No Prepubis Anchor
Pterosaurs extend their ventral muscle anchorage by adding a prepubis, which can be very long indeed in Rhamphorhynchus (Fig. 2) and Campylognathoides (Fig. 3). No muscles attach to the prepubis in Witton’s version (Fig. 1). One wonders why not, especially when the prepubes and femora are aligned during normal locomotion (Figs. 2-4).

Instead Witton 2013 follows Claessens et al. (2009) mistake when he reports the prepubes “were capable of moving up and down with each breath taken by their owner.” This “rotating prepubis” hypothesis was falsified earlier based on the Claessen et al. use of a flipped and partial prepubis to support their hypothesis. They got the bone upside down!! No other prepubes in any other pterosaurs support the Claessen et al. hypothesis. The pubis/prepubis joint is a butt joint in all pterosaurs. So it basically cannot move. The prepubis acted as an extension to the pubis. Pubofemoralis muscles probably extended down the prepubis as if it were an elongated pubis. Respiration occurred by expansion of the ribs, as in all tetrapods, not by the rotation of the prepubes. Correctly configuration shown below (Figs. 2-4).

The darkwing Rhamphorhynchus JME SOS 4785

Figure 2 The darkwing Rhamphorhynchus JME SOS 4785. Note the depth of the prepubis. Even if this prepubis could rock back and forth it would not further deepen the torso.

 The Pittsburgh specimen of Campylognathoides. This pterosaur had the largest prepubes of all pterosaurs. Note the ventral orientation, aligned with the femora during normal standing.

Figure 3. The Pittsburgh specimen of Campylognathoides. This pterosaur had the largest prepubes of all pterosaurs. Note the ventral orientation, aligned with the femora during normal standing. Note the butt joint between the pubis and prepubis.

The Triebold Pteranodon, one of the most complete ever found. The metacarpals are quite a bit longer here. So is the beak.

Figure 4. The Triebold Pteranodon, one of the most complete ever found. I have this skeleton cast. The prepubes extend ventrally, in line with the femora and unable to expand the torso during respiration. Expanding ribs, as in all tetrapods, provided all the necessary torso expansion for respiration.

Witton's prepubis mistakes, based on mistakes by Claessen et al. 2009. (Above) in Rhamphorhynchus the prepubis is waaaay too small. In both the prepubis is incorrectly oriented and incorrectly attached to the pubis.

Figure 5. Witton’s prepubis mistakes, based on mistakes by Claessen et al. 2009. (Above) in Rhamphorhynchus the prepubis is waaaay too small. In both pterosaurs the prepubis is incorrectly oriented and incorrectly attached to the pubis.

Elongate ilia
And why would the all pterosaur ilia extend so far anterior (especially so in Sos 2428), framing so many sacrals (Fig. 1), without bringing a few muscles with them? After all, that’s what mammals and dinosaurs do. And the muscles arising from the ilium in lizards concentrate anteriorly. Finding homologies and analogies is how we find the most parsimonious answer.

The missing caudofemoralis
Lizards and most dinosaurs have a robust tail with elongate transverse processes and deep chevrons. These are muscle anchors for the caudofemoralis, tail muscles that pull the femur posteriorly, contributing to the step cycle. In birds and pterosaurs these muscle anchors are largely, but not completely missing. The pelvis (and prepubis) have taken over those duties. The caudofemoralis is largely, but not completely missing in birds and probably pterosaurs. As in birds, pterosaur the anchoring transverse processes are vestigial or missing and their chevrons, where present, extend parallel to the caudal centra, not ventrally. In pterosaurs, chevrons are not caudofemoralis anchors, but secondarily adapted as tail stiffeners. They are essentially absent in basal pterosaurs, like MPUM6009. They redevelop in several taxa. These same caudal patterns (attenuated tails) are found in pterosaur precursors, the fenestrasaurs, evolving from less attenuated tails in tritosaur lepidosaurs, a key trait that ties them all together.

It’s important to examine living animals to see their muscle patterns in order to reconstruct them in prehistoric animals. It’s important to know what new bones, like the prepubis, are used for (not respiration). It’s important to note the details in a skeleton, establishing articular surfaces and creating accurate reconstructions.

References
Claessens, LPAM, O’Connor PM and Unwin DM 2009. Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism. PLoS ONE 4(2):e4497.http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004497
Romer AS 1971. The Vertebrate Body (shorter version). WB Saunders Co. 452 pp.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.x

Scathing Book Review – Pterosaurs (Witton 2013) – Dimorphodon problems

Updated June 10, 2015 with a revised Dimorphodon takeoff  (Fig. 3) that included a downstroke right at the start of the leap. 

Earlier we looked at the inaccurate cartoon produced of the hind-wing glider, Sharovipteryx by author and illustrator, Mark Witton.  Here we’ll continue up the phylogenetic line to consider the disfigurements Witton applied to a basal pterosaur.

As a purported pterosaur expert, Mark Witton, author of the new book “Pterosaurs,” should be able to accurately portray a pterosaur skeleton. Unfortunately his Dimorphodon drawing is filled with errors (Fig. 1). For comparison, an accurate portrayal based on a bone-by-bone tracing is shown below (Fig. 4).

Dimorphodon by Mark Witton, filled with errors.

Figure 1. Dimorphodon by Mark Witton, filled with errors. This pose does allow Witton to avoid the digitigrade and bipedal issues, which would be visibly odd if set in a standing pose. Is there any way this pterosaur could complete a pushup that would launch it into the air high enough to unfold that big wing finger before crashing to Earth. This is a risky move every time it’s attempted!

  1. Apparent mandibular fenestra – caused by a slipped surangular detailed here and confirmed by Bennett (2013).
  2. All pterosaurs have eight cervicals (prior to ninth vert with deep ribs)
  3. 1st and 2nd dorsal ribs should be hyper-robust and 2nd articulates with sternal complex
  4. Prepubis is the wrong shape and should articulate with the ventral pubis at its stem and against the edges of the last gastralia at its anterior process
  5. Caudal vertebrae should align with the sacrals with neural spines rising above the ilium
  6. The radius in all tetrapods originates on the lateral humerus, not the medial
  7. The pteroid should originates on the proximal carpal, not the preaxial carpal (Peters 2009, Kellner et al. 2012)
  8. Metacarpals 1-3 should align palmar sides down, out and away from metacarpal 4. This provides room for all four metacarpals to have extensors tendons.
  9. Following a wrong hypothesis, Witton orients his pterosaur fingers posteriorly, but all pterosaur tracks show digits 1-2 were oriented laterally and only digit 3  oriented posteriorly due to a spherical metacarpophalangeal joint, as in many lizards.
  10. Pedal digit 5 never flexes at pedal 5.1 (Fig. 1), but does flex nearly 180 degrees at pedal 5.2 in fossils (Fig. 4). Witton disfigured toe 5 this way in order to have it frame a uropatagium, as has been suggested for Sordes and MSNB 8950, but both are misinterpretations detailed here and here. The actual orientation of pedal digit 5 is detailed in Peters (2000, 2011, Fig. 4) and here and here.
  11. The tail and torso both appear to be too short. Freehanding, like Witton does, is not conducive to accuracy.

Forelimb pterosaur leaping
One of the hypothetical practices Witton endorses for pterosaurs across the board is the much promoted, but wisely criticized, forelimb launch. We’ve discussed its failing before. There is still no evidence for it in the fossil record, although Witton pins his hopes on a three-year-old rumor. Witton illustrates nearly all of his pterosaurs in the forelimb launch configuration (fig. 1). What Witton doesn’t show is what happens shortly thereafter. Here (Fig. 2) is Witton’s Dimorphodon trying to become airborne after attempting a mighty pushup with folded wings beneath its body and mighty triceps extensors working their hearts out. Forelimb leaping is also tremendously difficult for athletes as seen here. Click the image (Fig. 2) to animate it if not already animated.

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

Figure 2. Click to animate. 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, brings the pterosaur down. There’s just not as much leverage and musculature here as in the vampire bat, which can accomplish this leap. Human athletes cannot get this high. At the apex of this leap the wings are just beginning to unfold. Moreover those big wing fingers have to swing through a ventral arc before swinging above the torso prior to the first wing beat. Finally, there’s not much forward thrust here.

There has always been a better way for Dimorphodon to leap (Fig. 3), like a leaping lizard and the vast majority of all tetrapods: by using the hind limbs, like birds, frogs and kangaroo rats do.

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

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

Exceptions include tiny vampire bats (Fig. 4) which arrived at forelimb leaping secondarily, as a bi-product of their lifestyle and the extremely weak legs of bats in general. Primates, jumping rodents and flying lemurs are much better at hind limb leaping than bats are. Click here to see the video of the top 10 fastest, highest jumping animals.

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 4. 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, is way too 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.

Size matters!
Dimorphodon is not a large pterosaur. Even so, it is several times larger than a vampire bat (Fig. 4). Its not just the effect of gravity, which increases with the cube of height, but it’s also the cushion of air, that becomes so much more cushiony the smaller a creature gets and as it adds surface area. That’s why vampire bats can get away with forelimb leaping while pterosaurs larger than a vampire bat likely could not. And giraffe-sized pterosaurs could probably leap with their forelimbs about as high as a giraffe can leap with its forelimbs.

At least he’s consistent
Witton incorrectly pastes dorsal metacarpals 1-3 back-to-back against metacarpal 4 (now rotated palmar side posterior to enable wing folding, Fig. 1). That orients the free fingers palmside anterior during flight and all posteriorly when hyperextended during terrestrial locomotion (Fig. 1). Unfortunately that doesn’t match pterosaur handprints, which are lateral for digits 1 and 2 (sometimes anterior for digit 1) and posterior for digit 3 due to a spherical joint there. That also means when a pterosaur wants to clamber up a tree, it can’t because in Witton’s view the palms are face up, as if begging.

The better orientation is palm side down while flying (or palms medial (like clapping) when walking). That also gives all four forelimb digits plenty of room to have extensor tendons. The preferred configuration also means the fingers hyperextend laterally when walking with the exceptional digit 3 oriented backwards to match ichnites. Details here.

But not always consistent
Witton’s figure 7.10 has the palms facing each other while the pterosaur is floating. They should be palms up in his view.

Whether pterosaurs had their fingers oriented laterally or posteriorly, that’s arrived at secondarily, because no tetrapods do this plesiomorphically. Their fingers always point in the direction of travel. The secondary lateral placement of the fingers on the substrate occurred after a bipedal phase shown in Cosesaurus/Rotodactylus and emphasized in Sharovipteryx. In Witton’s hypothetical scenario, the one that ignores real fossils, pterosaurs and their ancestors were never bipeds.

Pterodactylus walk matched to tracks according to Peters

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

No Bipedal Footprints?
Along with the adoption of the forelimb launch, Witton (2013) rejects the bipedal capabilities of pterosaurs, first promoted by Padian (1983) and later by Peters (2000a, b, 2011). Peters (2000a, b) recognized that pterosaur tracks known at that time were all plantigrade and quadrupedal but recognized that pterosaurs anatomy could vary and that even the quadrupdal pose included having the toes directly beneath the center of gravity, the shoulder glenoid (Fig. x). That enabled the forelimbs to be raised without changing elevating the back. Witton ignored this data. He also reports there are no records of digitigrade pterosaurs, but his book includes an illustration of one (his figure 7.9) and he ignores the several digitigrade pterosaurs in other published works (Peters 2011, Fig. 5) mentioned, referenced and illustrated here, here, herehere and here.

Digitigrade pterosaur tracks

Figure 5. A pterosaur pes belonging to a large anurognathid, “Dimorphodon weintraubi,” alongside three digitigrade anurognathid tracks and a graphic representation of the phalanges within the Sauria aberrante track. Digit 5 impressing far behind the other toes is the key to identifying tracks as fenestrasaurian or pterosaurian.

Not Digitigrade? It pays to be specific here.
Witton referenced Clark et al. (1998) who reported that basal pterosaurs, like Dimorphodon, had flat feet because they could not bend the metatarsophalangeal joint due to the squared-off (butt joint) shape. Peters (2000a) showed that Cosesaurus, an ancestor to pterosaurs, had the same sort of butt-joint metatarsophalangeal joints, and that its feet exactly matched Rotodactylus tracks, but only when the proximal phalanges were all elevated (because they could not be bent), in accord with the findings, but not the conclusions of Clark et al. (1998). Peters (2000a) also showed that many pterosaurs, from Dimorphodon Pteranodon, raised the metatarsals and proximal phalanges in the same way to produce a digitigrade pes. The reduction of pedal digit 5 in derived pterosaurs led to their becoming plantigrade. Beachcomber pterosaurs also rested on their ski-pole like arms and became quadrupeds, but those forelimbs did not provide thrust due to the placement of the hands in front of the shoulder sockets.

Cosesaurus foot in lateral view matches Rotodactylus tracks.

Figure y. Cosesaurus foot in lateral view matches Rotodactylus tracks.

Ironically,
while Witton favors the archosaur model for pterosaur origins, he rejects digitigrade pedes in pterosaurs, a trait widely found in basal dinosaurs and basal bipedal crocs.

Bipedal capability (in the manner of modern bipedal lizards), a narrow chord wing membrane and twin uropatagia solve all sorts of problems introduced and sustained by Mark Witton and the other experts he hangs with. And, there’s fossil evidence for all of this (throughout this blog and reptileevolution.com)! And none for the Witton follies.

Extension and Flexion Forelimb Limitations
Pterosaur arms cannot fully flex if they have large pteroids. The elbow joint also prevents this. Pterosaur arms cannot fully extend due to elbow limitations and the presence of the propatagium, which, as in birds, prevents overextension. These problems limit the ability of the forelimbs to flex and extend completely, like frog legs, to produce the best leap possible.

No Such Limitations in the Hind Limb
Simply leaping (or running and leaping) gets the job done so much better than an exaggerated pushup. Like birds, pterosaurs used their wings to flap and fly. That thrust can be employed during the initial hind limb leap, but not during the initial forelimb leap.

Leaping Lizard
If you want to have a good laugh while watching a rather ordinary lizard leap 3x its body length, check out this YouTube video. Just think how far a pterosaur could leap with those much longer frog-like hind limbs and elongated hips providing power at the femur, the tibia, the metatarsus and the toes in coordinated fashion, accentuated by powerful thrust provided by large flapping wings.

References
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Kellner AW, Costa FR, and Rodrigues T. 2012. New Evidence on the pteroid articulation and orientation in pterosaurs. Abstracts, Journal of Vertebrate Paleontology.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Peters D 2011.  A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos, 18: 2, 114 —141

Mark Witton’s “Pterosaurs” – a book review part 1

Dr. Mark Witton is fantastic artist and devotee of pterosaurs. He has a new book called Pterosaurs (with an Amazon.com preview). I’ve ordered the book and will make an in depth report after it arrives. The following is based on the online preview of chapter 1. Witton’s writing style is entertaining and engaging. The book should have popular appeal on that level.

The cover portrays a magnificent crested Nyctosaurus at sunrise or sunset. Gorgeous!

Then things tumble.

Witton’s Table of Contents shows an embryo Pterodaustro with a very short rostrum, unlike any Pterodaustro I’ve ever seen. And I’ve seen the embryo. The rostrum extends nearly the entire length of the egg. An agreement with Laura Codorniú prohibits me from publishing the image until she does, but the reconstruction of the long-beaked embryo Pterodaustro is based on that tracing. As we learned earlier, pterosaurs grew isometrically, resembling their parents on hatching.

Witton’s Rhamphorhynchus image on page 2 portrays the infamous cruro/uropatagium, a membrane spanning the hind limbs and not including the tail. The image also includes the infamous deep chord wing membrane, for which there is no evidence whatsoever as the Sordes situation was falsified. Witton’s two Rhamphs also have much shorter wings than any Rhamphorhynchus I’ve ever seen. One of Witton’s wonders has brought its wrists (carpals) in close to the base of the neck, which is novel, at least, but kills the tension on the extensor tendon that keeps the wing membrane aerodynamic. As in birds, when the elbow flexes, the wing folds. Having the wings fold in flight isn’t bad. Birds do it all the time for a brief low drag rest. At least the feet are properly positioned in Wittons’ illustration.

Page 3 portrays several dozen pterosaurs doing the forelimb leap that is such a travesty and fantasy that I slap my head every time I see it again and again. It has become firmly entrenched. Gadzooks@!# what is the ptero-world coming to?

Page 4 has a fine picture of Pterodactylus antiquus, the first pterosaur known to science, with a big round head crest. Not quite ready to buy into that one quite yet. Some Pterodactylus did have a crest, but not that one.

Page 12 portrays a hypothetic pterosaur ancestor. It looks like Peteinosaurus with a short digit 4 leaping from a branch (using muscular hind limbs). The caption reads, “The fossil record has yet to reveal an “intermediate” between fully formed pterosaurs and possible ancestors, meaning we can only speculate on their anatomy and appearance.” And once again, pterosaur professors are casting a blind eye toward the hard evidence presented in the large reptile tree where dozens of ancestors are lined up. As you’ll recall, ludicrous as it sounds, we can even put turtles up as the closest known sisters to pterosaurs if we delete all the other sisters and candidates from the new Lepidosauromorpha, as demonstrated here. This just proves that pterosaur workers are actively avoiding the issue and the answer. But, I have to say, it’s a beautiful and evocative image that Witton has created, wrong though it may be.

Page 16 portrays three purported pterosaur ancestor/sisters, Sharovipteryx, Euparkeria and Scleromochlus. Witton calls Sharovipteryx an archosauromorph protorosaur, when it is neither. It is a fenestrasaur tritosaur lepidosaur, as we learned earlier. Euparkeria is closest to erythrosuchids, about as far from pterosaurs as one could imagine. Scleromochlus, shown hopping in Witton’s illustration with a dino quadrate leaning the wrong way, is a basal crocodylomorph. Witton strongly leans toward the “pterosaurs are ornithodires” direction despite the tiny hands and lack of pedal digit 5 in Scleromochlus.

Witton takes aim at my placing pterosaurs within the Squamata as the most unlikely hypothesis currently under consideration. See a recent post on this here. Witton writes, “There seems little similarity between the skulls of pterosaurs and the highly modified, mobile skulls of squamates or any similarity between the trunk and limb skeletons of each group.” Well, frequent readers will know that pterosaurs are tritosaur lepidosaurs, an outgroup clade to the two that make up the Squamata, the Iguania and the Scleroglossa. Pterosaurs are neither of these. Tritosaurs do not have the mobile skulls found in some squamates. They also don’t have the fused tarsals of squamates. They are distinct. Witton has whitewashed the tritosaur fenestrasaur hypothesis with this “red herring,” while virtually ignoring the fenestrasaurs, following in the less than noble footsteps of our colleague Dr. David Hone, whose exploits you can read about here. In chapter one, at least, Witton avoids any discussion of the pteroid and prepubis in Cosesaurus and other fenestrasaurs. Why should he ignore these key and readily observable traits? Dr. Pierre Ellenberger saw them first without recognizing their significance.

Page 17 Witton then discusses the possible protorosaur origins of pterosaurs, pointing to the shared trait of an elongated neck and forgetting the not-so-elongated neck of the basalmost  pterosaur, MPUM6009.  Witton points up the “fact” that protorosaurs lack an antorbital fenestra, but recent finds show that two protorosaurs had such a fenestra by virtue of convergence (really a side issue of little consequence). Witton finishes with protorosaurs by noting the body shapes are not at all pterosaurian, which is true.

Witton invites a closer look at Sharovipteryx and notices similarities to pterosaurs in the hind limbs and their membranes, but notes, “It’s hard to find other features that reliably link this animals with pterosaurs.” He may not have looked at the actual specimen as I have. Evidently he did not notice the ilium was anteriorly elongated, prepubes were present, more than five sacrals were present, the tail was attenuated with parallel chevrons, the bones were hollow, the feet have the same morphology as pterosaurs with a short metatarsal 5 and an elongated and robust p5.1 as obvious and compelling similarities. Once again, the blind eye rules. Witton reports that the Sharovipteryx skull lacks an antorbital fenestra and the foot is unlike that of any pterosaur. Where does he get his information? Certainly not from any sort of direct observation or adherence to the literature. Of course he doesn’t back up any of this with evidence. Witton concludes by noting that gliding with hind limbs is unique, failing to find parallels in Microraptor and the uropatagia of fenestrasaurs including pterosaurs. Sharovipteryx had fore limbs. Witton just doesn’t know or doesn’t show what they look like. But you can see them here.

Page 18 Witton prefers the archosauriform ancestry hypothesis due to the shared features of an antorbital fenestra and reduced bone counts in the fifth pedal digit, perforated lower jaws, and “many other anatomical similarities.” Really? Witton equates an evaporating pedal digit 5 in archosauriforms with the robust element in pterosaurs (and, of course he doesn’t count the ungual on the pterosaur digit). A robust pedal digit 5 is also found in Huehuecuetzpalli and all the tritosaur lepidosaurs that followed (except Macrocnemus and the drepanosaurs). Why doesn’t Witton consider these and put some study into them? The antorbital fenstra of archosauriforms is always (except for proterosuchians) surrounded by a fossa, a trait lacking in any pterosaurs.

Witton also prefers archosaurs as pterosaur sisters, and, in particular, Scleromochlus, despite the tiny hands that were, ironically, used to rule out Sharovipteryx. Evidently Witton prefers to have it both ways, so long as he stays within tradition. Witton lists fusion of the two proximal ankle bones to the shin (which does not occur in pterosaurs), reduction of the fibula (also in tritosaurs), the structure of the foot (actually more like that of tritosaur lizards like Cosesaurus, which retain an elongated pedal digit 5, which archosaurs lack), “several limb and hip proportions” (can Witton get even more vague here?) and the lack of bony scales along the back (then why is he ignoring those on Scleromochlus and Scutellosaurus).

Witton notes the shield-like pelves were different than in dinosaurs, but defends that by saying, “This may not be surprising, however, given, that pterosaur hindlinmbs were, uniquely among ornithodirans, used to support the wing in flight.” Utter rubbish!!! on the face of it and not pertinent to any phylogenetic discussion. You take the traits as they are and you let the computer decide where the taxa belong most parsimoniously. The “why” question or reason is never in play. By the way, similar pelves to pterosaurs can be found in fenestrasaurs, but these are ignored by Witton.

Witton writes, “arguments that basal pterosaurs were bipedal and digitigrade may be flawed” because basal ornithodires (aka: Asilisauruswhich bears no resemblance whatsoever to pterosaurs) were quadrupeds. This is far-reaching and totally bogus. I would be ashamed and would expect heavy chastisement having made such a comparison, especially after promoting bipedal Scleromochlus as a potential ancestor. But then Witton tops that bungle of reasoning by saying that Scleromochlus is “suspected of hopping about on plantigrade feet.” More fantasy! Few creatures, other than deer and horses, have feet more obviously digitigrade than Scleromochlus. Witton also ignores the known bipedal pterosaur footprints  (more here, here and more info here).

Page 21 Witton prefers an imagined hypothetical ancestor to a real one, and it glides from trees. Of course, this does nothing to explain the origin of flapping (because no gliders flap, unless they started off as flappers). Witton ascribes the mobility and length of the fifth toe to its use as a stabilizing tool, ignoring the fact that most tritosaurs from Tanystropheus to Sharovipteryx, have such a fifth toe, thus it cannot be developed for flight. Witton reports that the fifth toe, which is lateral, elongates to frame the medial membrane, which should strike you as odd and implausible. In reality the fifth toe is not connected to a membrane, except in Sharovipteryx, and each membrane trails each hind limb. They don’t cross to connect with each other.

Page 22 Witton reports that the hind limbs rotate out sideways to create efficient airfoils, but even that is fraught with error. One: Archosaurs can’t do this with their erect femurs. Two: Basal pterosaurs can’t do this either with their erect femurs. Raising the hind limbs to the horizon happens in later, more derived pterosaurs with a more sprawling femur.

Witton reports that during the evolution of pterosaurs that the fourth finger became so enlarged and unwieldy that it needed to be stowed away when grounded. We can all stow away our fingers by pressing them against our palms, but Witton ignores this. He also ignores the axial rotation of metacarpal 4 so that digit flexion puts digit 4 along the posterior rim of the hand, not the palmar side any longer. Witton reports ungual 4 was missing, since it was no longer necessary. We’ve seen so many several cases of ungual 4 present on pterosaurs that it needs to be considered universal.

Witton adds fibers to wing membranes as they need to be more sophisticated in their unsupported regions, ignoring that Cosesaurus had trailing fibers before it had wing membranes (Ellenberger 1993, Peters 2009).

With regard to flapping, our expert Dr. Witton reports, “At some point, manipulation of these wings in the vertical plane produced flapping, and self-propelled flight was achieved.” Gee, he makes it sound almost as if it was that easy. At ReptileEvolution.com and the PterosaurHeresies blog you learned the exact steps the exact taxa took to achieve flapping prior to the development of wings in pterosaurs, paralleling that same development in birds. So if Witton’s book leaves you unsatisfied and yearning for real answers, come see these websites and blogs.

Witton ascribes the development of flight muscles and bones to the ability of quadrupedal pterosaur ancestors to chiefly employ the forelimbs during leaps. He sort of leaves the larger hips and thighs out of the equation, evidently incapable of creating all the power necessary for a leap and leaving the unused arms in this bipedal model to do something else, like flap as a secondary sexual trait.

Dr. Witton does take the brave leap of including my published works in his reference list, something Dr. Unwin did not do in his less recent pterosaur book.

Let’s face it
If Dr. Witton does not even know what pterosaurs are (which he has acknowledged in his book), he has no business acting as an expert on pterosaurs and writing books about them. Unfortunately this is an acceptable trend continued by Dr. Unwin from Dr. Peter Wellnhofer. In chapter one Witton has already published too many errors. It’s too late in the game to fold ones’ hands and politely tell your readers, “Good question… we really don’t know. It’s one of the mysteries of paleontology.” There’s something called phylogenetic analysis that is guaranteed to give you an answer when you’re looking for an ancestor. However, you’ll have to include at least a few of the right taxa (among the tritosaurs in this case), to get close to the right answer. If you’re looking for the ancestors of pterosaurs, they’re right here in one place.

We’ll look at other Witton chapters in the future. But this one on pterosaur origins really irks me. It’s rather embarrassing that this sort of crap (a complete avoidance of certain data) is still being circulated. But I _do_ love the artwork.

References
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.