Scathing Book Review – Pterosaurs (Witton 2013) – Wing membrane mistakes

Earlier here, here, here, here and here we looked at the new book, “Pterosaurs” by Mark Witton (2013) and the many problems, mistakes and oversights that book contains. Today we’ll look at how Witton attempts to support the traditional hypothesis of a deep chord wing membrane attached at the ankle (Fig. 1). We covered that topic earlier here.

Figure 1. From Witton (2013) the Vienna specimen of Pterodactylus with a beautifully preserved wing membrane that is shallow at the elbow, stretched between the wingtip and elbow  and includes a small fuselage fillet back to mid thigh.

Figure 1. Click to enlarge. From Witton (2013) the Vienna specimen of Pterodactylus with a beautifully preserved wing membrane that is shallow at the elbow, stretched between the wingtip and elbow and includes a small fuselage fillet back to mid thigh. Witton’s caption indicates the ‘in vivo’ wing membrane is not accurately represented here ‘in situ’. He considers the membrane, “somewhat desiccated, shriveled.” So, what happens when the data doesn’t fit the hypothesis? Witton blames the data. The uropatagium and toe webbing, by the way, were unaffected.

When a bad hypothesis meets good data
Witton (2013) upholds the deep chord wing membrane hypothesis. So when excellent data indicates a shallow chord with fuselage fillet (the Stromer model, Fig. 8), Witton invents excuses for it (Fig. 1), calling it “dessicated” and “shriveled.” There are no other examples of desiccated membranes in pterosaur fossils. In any case, wing membranes contained little water in life, so how could they shrink when desiccated, especially when buried underwater? Adding to the confusion, on the same page (Witton 2013: 196), he illustrates a nicely preserved uropatagium and webbed toes from the same specimen. These, strangely enough, have not suffered at all from desiccation!

To clarify things
Peters (2002) published an image (Fig. 8) of what happens when the Vienna specimen unfolds its wings. Here it is animated (Fig. 2). Witton ignored this paper.

The Vienna Pterodactylus.

Figure 2. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. There is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

The real wings, based on the excellent data provided by the Vienna specimen, demonstrate the membranes were stretched between the wingtip and elbow, not the ankle.

Note: In all pterosaurs (Fig. 2) the wings were functionally disconnected from the hind limbs (contra the traditional view upheld by Witton), which means pterosaurs would have no trouble running around on the ground, bipedally or quadrupedally.

Witton (2013) misinterprets the pterosaur wing membrane
Earlier here and elsewhere we looked at the true shape of pterosaur wing membranes. Unfortunately, Witton (2013) promotes a completely different view. And this is not just a matter of opinion or sides in an argument. This fact vs. fiction (Fig. 1).

Pterosaur wing membranes according to Witton (2013). Mistakes here include the 1. deep chord wing membrane attached at the ankles, 2. trailing edge structure, 3. single uropatagium on Rhamphorhynchus.

Figure 3. Pterosaur wing membranes according to Witton (2013). Mistakes here include the 1. deep chord wing membrane attached at the ankles, 2. trailing edge structure, 3. single uropatagium on Rhamphorhynchus.

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

Figure 4. Here’s how the wing membrane in pterosaurs virtually disappeared when folded. There is absolutely no connection of the wing membrane to the ankle. Rather it goes to the elbow, as shown here, then to mid thigh as a fuselage fillet. Note how readily it disappears when folded!

The Zittel wing

Figure 5. The Zittel wing from a species of Rhamphorhynchus. Click to enlarge. Here it is more than clear that the wing is very shallow at the elbow. There’s the humerus. All that’s missing is the body. Here the wing is stretched between the wingtip and elbow. What could be more clear? I’ve added a body (Fig. 8) if you really need one.

Non-believers
Upon seeing this image (Fig. 5) promoted as a great example of a narrow-chord wing membrane, Darren Naish considered this “ambiguous” because the specimen has no torso (Fig. 8). Why do you need a torso? You have the entire wing! And it follows the Vienna Pterodactylus (Fig. 1) configuration – narrow at the elbow (and the BRI 010 specimen, see Fig. 6!). There’s no trailing membrane here that – can – extend to the ankle (Fig. 8). There’s no example of such a wing membrane anywhere, except, to some eyes, in Sordes. But that was demonstrated to be due to a disarticulated radius and ulna, which can be identified in the fossil.

Now, just to be fair and open, 
Helmut Tischlinger kindly sent me a short paper (Monninger et al. 2012) describing a new Rhamphorhynchus specimen BRI 010 (Fig. 6), in which “a linear structure runs along the trailing edige from the ankle to the tip of the wing finger.” That’s exciting. If verifiable, this would support the Witton model. Unfortunately, requests for hi-rez images of this specimen have gone unanswered. But I can present the image in low resolution from the abstracts, which are available online.

Rhamphorhynchus BRI 010. Here, unfortunately, the ankle is preserved right next to the elbow. Notably the wing membrane makes a beeline for the elbow, not curving posteriorly to meet the ankle. This is what we also see in the darkwing Rhamphorhynchus.

Figure 6. Rhamphorhynchus BRI 010. Click to enlarge. Color added. Here, the wing was reported to extend to the ankle. Unfortunately, the ankle is preserved right next to the elbow. Notably, the wing membrane does make a beeline for the elbow, not curving posteriorly to meet the knee. This is the configuration we also see in the darkwing Rhamphorhynchus.

Even at low resolution
we can tell that this is a Rhamphorhynchus with a well-preserved wing membrane with a trailing edge directed precisely at the elbow, as in the darkwing Rhamphorhynchus. Unfortunately the ankle has swung forward to the elbow. If the narrow-chord wing is correct, then this image needs no further explanation. If the deep-chord wing is correct we should see some sort of bending or curving toward the knee of the trailing edge (as shown in Fig. 3), but there is none.

Thank goodness!
By the text of the short paper I thought I was going to have to apologize to the pterosaur experts.

Linear structure on the trailing edge?
I can’t comment on the linear structure along the trailing edge, having never seen one, but then I haven’t seen this specimen in high resolution either. We’ll have to wait.

Pteroid location
As part of the leading edge, the propatagium and pteroid are also important aspects of the pterosaur wing. Witton (2013) ignored the evidence and his own text that the pteroid articulated with the proximal carpal (radiale) and instead sometimes illustrated it in the cup of the preaxial carpal (Fig. 7), sometimes locating it on the radiale, sometimes on the distal carpal. His text does report the preaxial carpal articulated with the distal carpal, so why the imprecision? Witton reports the pteroid “probably articulated in a depression on the medial side of the preaxial carpal (Bennett 2007) and MAY have also contacted the proximal syncarpal (Peters 2009).” Actually, with the way the wrist bent, the pteroid would rarely if ever contact the preaxial carpal. They diverged from one another and were separated by the length of the proximal and distal carpals.

Dimorphodon by Mark Witton, filled with errors.

Figure 7. Dimorphodon by Mark Witton, with the pteroid articulating with the cup of the preaxial carpal.

Pteroid origin
Witton did not report the pteroid and preaxial carpal were present on Cosesaurus (Peters 2009), first observed but misidentified by Ellenberger (1993) who, unfortunately, flipped that manus over in order to have digit 2 longer than the lateral digits.

Anyway, a series of errors over time ultimately brings us to the truth of what is actually happening with the wings of pterosaurs, a configuration first envisioned by Stromer in 1910 (Fig. 8b).

The Vienna wing and the Zittel wing.

Figure 8. Click to enlarge. The Vienna wing and the Zittel wing. Both Zittel and Peters 2002 added a body to the Zittel wing and arrived at the same unambiguous conclusion. The caption within the figure provides details.

References
Monninger S, Frey E and Tischlinger H 2012. Supporting structures in the flight membrane of pterosaurs. EAVP abstracts, Teruel, España. Royo-Torres, R., Gascó, F. and Alcalá, L., coordinators. 10th Annual Meeting of the European Association of Vertebrate Palaeontologists. ¡Fundamental! 20: 1–290.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
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.

4 thoughts on “Scathing Book Review – Pterosaurs (Witton 2013) – Wing membrane mistakes

  1. No, this is assuredly NOT “fact vs fiction”. It is “difficult to interpret taphonomy” vs “the Dave Peters magic-eye technique”. You are again making claims that are simply assertions and cannot be accepted at face value. Example 1: “There are no other examples of desiccated membranes in pterosaur fossils”. Oh really? And how do you >know< this? Example 2: "wing membranes contained little water in life". They're made of skin and other tissues, so are you sure about this? (aren't epidermal cells like… 95% water?). Example 3: "how could they shrink when desiccated, especially when buried underwater?". How do you know that this specific pterosaur's taphonomic history was spent entirely in water? Have you heard of osmosis? In fact, do you even know that water can be lost from tissues in a hypersaline environment?

    On the Vienna wing, it is indeed ambiguous (thank you for sort-of quoting me on this, even though you linked to another of your own blog articles): you consistently fail to note or acknowledge that it was extensively 'prettied up' between discovery and publication. In fact, we know that it was EXTENSIVELY MODIFIED by preparators, with much of its original surface layer and even parts of the membrane edges removed entirely!!

    Again, Cosesaurus does not have the pteroid and such that you say it does. Petersland = not the same as reality.

    Again, I am really bothered by the fact that what you've titled a 'Scathing book review' is, in fact, an assemblage of your idiosyncratic musings and pet ideas. You are being intellectually dishonest.

  2. If the Vienna Pterodactylus was extensively modified, then kindly send me to the reference from which you get your data. And the question is always, “how so?” Your ‘all caps’ suggests to readers that it was massive destruction (and to what end or motivation??), when, it may have been simply removing matrix here and there. At this point, I find your insinuations without evidence unbelievable in light of the fact that ALL other pterosaurs (see above) exhibit this wing configuration. Send me the evidence and lighten up on the insults or you’ll be put on the spam list. You’re showing signs that you may be the one who is being intellectually dishonest, especially so when slinging insults instead of data.

    Re: Cosesaurus, you haven’t seen the Ellenberger illustrations of the pteroid and preaxial carpal? There are only two people who have published extensive works on Cosesaurus. Both of us made mistakes rectified recentlty by experience and new insight. Even so, I invited you to toss out any traits you deemed bogus and there’s still a long list of traits that make Cosesaurus the Archaeopteryx of pterosaurs. Why is this extremely important fossil being ignored by fossil workers? Would the world collapse if I was right?

  3. “No cases of desiccated membranes in pterosaur fossils”

    Ah yes, you suppose that animal corpses probably floating and showing obvious signs of decomposition would have retained the exact wing shape as in life.

    Then again, the concept of post-mortem alteration is alien to you. Nearly all of your nonsense relies on ignoring it.

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