The reason and soul of PterosaurHeresies is to reveal the flagrant and untenable errors that continue to float around pterosaurs (in particular) and prehistoric reptiles (in general). We’re not just sniping here. Evidence is always provided when a case is made. And we do provide credit where workers have done their homework.
Here we’ll document some of the worst efforts wrought by experts in the ptero trade.
Case in point:
This YouTube video of an ornithocheirid pterosaur walking (Fig. 1) almost could not be worse. Unfortunately it was based on “expert testimony” from notable experts (see below). It might also owe some due to the Walking With Dinosaurs series from the BBC, which featured a similar giant ornithocheirid.
Figure 1. Pterosaur walk cycle posted on YouTube. Click to view. While following conventional thinking, this model demonstrates exactly why the hypotheses it is based on are so wrong.
1. Wing membrane attached to the ankles – not found anywhere in the fossil record. Awkward as hell as you’ll see it in action when you click on the video.
2. Fingers pointing forward – ichnites say laterally to posteriorly.
3. Pteroid pointing forward – all fossils indicate medially, but many papers indicate anteriorly
4. Wing folding – needs to butt up against the metacarpus and ulna as fossils show
5. Convex neck – all fossils show a concave dorsal neck
6. Hind limbs – way too robust. Should be mere sticks with tiny feet, smaller than shown.
7. Skull way too small
1. Widely splayed femora.
2. Upright torso
3. Elbows back
4. Robust thighs
Don’t Blame the Artist (too much)
He or she was only following the conventional thinking of today’s pterosaur experts, the ones who are ruining pterosaurs right before our eyes by producing visions of walking pterosaurs that do not follow the evidence. In many cases, there is a flagrant disregard and internal inconsistency.
Case in point
In Dr. David Unwin’s book The Pterosaurs From Deep Time (p201), he promotes this image (Fig. 2) as “Restoration of Anhanguera (Fig. 3) in the posture that pterodactyloids are now thought to have adopted while walking.”
Problems with this figure
Figure 2. According to Unwin 2006, this is the posture that “pterodactyloids are now thought to have adopted while walking.” It is based on Bennett (1991, figure 4). However, the position of the elbows here contradicts his text, which states, “[the humerus] lay nearly parallel to the body.” If you put your elbows out, which way to your fingers turn? In, not out. It takes maximum pronation to make them turn out again.
1. Lacks metacarpals 1-3. Lacks distinct phalanges on manual digits 2 and 3.
2. Pteroid articulates with tip of preaxial carpal
3. Elbows anterior to shoulders (try it yourself to see how awkward this is)
4. Feet way too big
5. Knees not aligned with prepubes, which are missing
6. Femora not bowed (so that axially aligned head fits into acetabulum socket)
7. Pelvis incorrect (looks like a Germanodactylus
8. Humerus too small
9. Sternal complex too flat (looks like a Pteranodon
10. Too few ribs
Here’s what Anhanguera should look like:
Figure 3. Anhanguera. Note the tiny feet, the bowed femora, the elbows back (the way Unwin described them but did not draw them), etc. etc. In this pose it’s not clear that manual digit 1 would ever touch the substrate, but then only individual pedal ichnites are known for ornithocheirids, no trackways.
Derived from Bennett 1991
Unwin’s 2005 figure was based on Dr. Chris Bennett’s 1991, 2000 reconstruction (Fig. 4) of Pteranodon, which had all of Unwin’s faults and a few of its own. The finger’s on Bennett’s Pteranodon faced palmar side up because Bennett mistakenly reconstructed the metacarpals palmar side forward while flying. We discussed problems with that hypothesis earlier. See a couple of good Pteranodon post-crania here. See some more or less complete Pteranodon here and here.
Figure 4. Bad Pteranodon reconstruction from Bennett 1991, 2000 in which the fingers faced palmar side up and the elbow bent at an impossible angle with regard to the shoulder joint. Unwin (2005) replaced the skull and flipped the hand. Due to the saddle-like shape of the shoulder joint, rotation should have been impossible, but Bennett ignores this.
Dr. Unwin’s Robodactylus
Unwin (2006) reports that Don Henderson and he “had our first baby.” It was a computer generated walking Anhanguera, they called Robodactylus that was differently configured than his illustration (Fig. 2), but still ignored many morphological traits.
Figure 4. Robodactylus. This is one frame in a walking sequence that is supposed to represent Anhanguera. After tilting the backbone up, “Suddenly it all fell into place,” according to Unwin. Note the incorrect parasagittal hind limbs and the improved “elbows back” posture. A careful look reveals the wing fingers are anterior to the forelimbs, which is a result of oversimplification while making the model.
I remember seeing the Henderson/Unwin presentation and shaking my head at how Frankenstein-ish it appeared. The worst aspect of this model is the position of the hind limbs in the parasagittal place. The best aspects include the elbows back and elevated torso. However, the elbows should have been almost straight below the shoulders (fig. 3).
But wait, it gets worse
After tackling Anhanguera, Henderson and Unwin digitized Rhamphorhynchus to create Roborhamphus (Fig. 5). Remember that Unwin (2006) thinks that all basal pterosaurs had a membrane that extended between the hind limbs (including pedal digit 5) and tail based on his misidentification of features in Sordes. He reported, “Effectively, in these early pterosaurs, all four limbs [and the tail] were linked to one another.”
Linking the hind limbs to a tibia’s length of tail with uropatagia is how Henderson and Unwin decided the tail was unable to rise at its base. This is their infamous “raincoat test” that shows how awkward and bound up early pterosaurs were in their view. All this disfigurement is all due to Unwin’s misinterpretation of Sordes and the importance he gave it, trumping all other evidence (Fig. 6b).
Figure 5. Roborhamphus. This is how Henderson and Unwin animated Rhamphorhynchus during a walking cycle. Hmm. If this is right, then maybe pterosaurs did indeed share a recent common ancestor with parasuchians. (jess kiddn) Good luck getting Roborhamphus off the ground! They reported they could not raise the torso without “the tail bashing into the ground.” This pose, to their surprise, worked. Here the feet appear to be way too small, perhaps cheated to enable a recovery stroke without too much toe drag. Not sure if the wings are foreshortened in this view, but they should be much longer (see fig. 6).
Figure 6. The darkwing specimen of Rhamphorhynchus muensteri demonstrating more accurate proportions, a little chubbier than Roborhamphus with longer wings and a bendable tail base. The uropatagia do not bind the hind limbs and the wing does not attach to the hind limbs.
Here’s the real darkwing Rhamphorhynchus (Fig. 6, 6b) based on DGS with its torso and tail raised. It’s those little bendable proximal caudals that enable the tail to rise, pulled by sacral muscles that Henderson and Unwin did not consider. In the Henderson/Unwin model (Fig. 5) Unwin (2006) reported, “Remember that the body, neck and head lay in almost a straight line in these animals (as also for example in lizards and crocodiles), and this fitted neatly with the horizontal walking posture of Roborhamphus.” Like birds, that’s not true of any pterosaur, except, perhaps, while flying.
Figure 6b. Wing membranes and uropatagia in a basal pterosaur, the darkwing Rhamphorhynchus. The uropatagia did not connect to the tail, only the pelvis, so the tail could rise as in figure 6. The wing membrane does not attach to the ankle. Those patches that appear to do so are body fluids fossilized by bacterial activity. They have no wing structure to them.
Dr. Mark Witton will soon have his pterosaur book out. Previews can be seen here. This is the Witton and Naish (2008) vision of a walking Zhejiangopterus pterosaur (Fig. 7) published in Naish’s blog.
Figure 7. Click to follow link. A walking Zhejiangopterus (Witton and Naish 2008). Here all four limbs are planted at the same time. The foot-to-foot distance is much larger than the hand-to-hand distance. This configuration also plants the manus anterior to the pes, which is the opposite of what we see in fossil ichnites. By elevating the backbone all problems are solved. The outstretched and cantilevered neck is also a potential problem, like the Kent, Stevens sauropod neck in the ONP (osteologically neutral pose) rather than the more biologically followed (OEP) osteologically elevated pose (see fig. 4), promoted, ironically, by Taylor, Wedel and Naish (himself, 2009). The depth of the pelvis is far too shallow here. See figure 5 for an alternative stance. Try walking with your arms at length in front of you while you walk and see how quickly the lactic acid builds up. Then imagine putting the weight of a large skull at the end of six-foot-long arms and you’ll get an idea how quickly tiring this Witton and Naish pose would become for this poor azhdarchid.
Not sure why Witton and Naish (2008, Fig. 7) tried to promote their hypothesis of a walking pterosaur by planting all four feet on the ground in a pattern that does not fit known ichnites or tetrapod walking cycles. Two of those limbs need to be elevated (recovery phase). In order to match tracks that place the manus print just aft of the pedal imprint the backbone needs to be elevated (see animation, fig. 10). The knees need more bend on initial contact. The neck also needs to be elevated, following hypotheses in Naish’s own work (Taylor, Wedel and Naish 2009).
No Bitching Without A Solution
Here (fig. 8) and here (running Quetzalcoatlus) all the problems are solved. The neck is held high. The wings are completely folded. The manus could easily impress behind the pes (as in Fig. 10). The fingers extend laterally to posteriorly. The foot and hand both have recovery phases. The center of gravity is just anterior to each footfall, as in humans. The hands are like ski poles, not contributing to thrust. And this pterosaur (figs. 8, 10) is ready to take off from a standing start. You can see the animated model (fig. 10) matches the tracks in morphology, size and gait.
Figure 8. Click to enlarge. There are several specimens of Zhejiangopterus. Here I am showing the standing pose with that giant skull better balanced over the body and, with bent knees and and upright torso, these feet are able to implant just in front of each hand while walking. And this pterosaur is ready to spread its wings and fly after launching itself with those huge thigh muscles.
Figure 9. 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. At least one foot is off the ground here. That’s a positive. Note the wing membrane behind the elbow: nice!! But also look at how far that fuselage fillet has to stretch here. Untenable. See Figure 10 for a more upright solution.
The same problems attend this poor chap (Fig. 9) with the horizontal backbone. At no time in the step cycle of this pterosaur are those forelimbs going to provide thrust, but rather braking. Pterosaurs were secondarily quadrupedal and many could go both ways. Not sure why workers insist on giving pterosaurs a horizontal backbone. Matching the skeleton to tracks (Fig. 4) is easy to do and gives much more tenable results.
Figure 10. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks
Ichnites don’t tell how long the implantation of the manus was. Here that time appears shorter than the implantation of the foot. The manus steadied the pterosaur while applying no thrust.
Earlier we covered bipedality and quadrupedality in pterosaurs here. We covered bipedal take-off in pterosaurs here and here. Tomorrow we’ll take on more monstrous reconstructions.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.
Witton M and Naish D 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271