Zittel Wing – Rio Ptero Symposium

Earlier we looked at another Rio Ptero Symposium abstract. There are several more to come.

Chris Bennett (2013) took a fresh look at the century-old Zittel wing of Rhamphorhynchus (Fig. 1). He determined that we need to flip our view of it. According to Bennett, those aren’t straw-like actinofibrils ribbing the wing that contract to make the wing extensible. Rather those are narrow spaces between popsicle-stick like actinofbrils that make the wing “inextensible.”

Figure 1. The Zittel wing simply flipped to give the impression of dips (upper image) or ridges (lower image) in the wing membrane due to shadows that the eye assumes to come from above the image.

Figure 1. The Zittel wing simply flipped to give the false image of dips (upper image) or true image of ridges (lower image) in the wing membrane due to light direction that the eye assumes to come from above the image. Note the round bones give away the true light direction. Inserts show Bennett’s new view (upper image) of wide aktinofibrils. Lower image shows traditional view of straw-like aktinofibrils that enable wing reduction.

Bennett notes, “actinofibrils were long flattened bands of keratin” and “The raised longitudinal strips are not the actinofibrils, but rather the grooves between the ridges are impressions of the actual actinofibrils and thus for 120 years we have had it upside down and backwards” and  “Thus its size and shape of the Zittel wing is essentially as in life.” Of course that flies against all the other examples of pterosaurs in which the wing folds to near invisibility.

This is not Bennett’s first foray into radical and irrational hypotheses. His autapomorphic interpretation of the flathead anurognathid skull and his completely imaginary hypothesis on pterosaur wing origins are among his earlier ventures. It’s hard to reconcile Bennett’s inextensible wing with the several other examples in the fossil record of extensible wings that collapse into almost nothingness.

On the other hand
in the same Rio Ptero volume Bennett successfully argued against the presence of an antorbital fossa and mandibular fenestra in basal pteros, as discussed earlier here.

Bennett SC 2013. If 6 was 9: Turning our interpretation of the Zittel wing upside down. Rio Ptero 2013 Short Communications. 22-25.


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