Reinterpreting pterosaur wings – svp abstracts 2013

The Vienna Pterodactylus.

Figure 1. The Vienna Pterodactylus. Click to animate. Wing membranes in situ (when folded) then animated to extend them. Bennett 2013 confirms this wing morphology, previously and mistakenly attributed to “membrane shrinkage” by Elgin, Hone and Frey 2011 . The static images are from Peters 2002.

From the abstract
Bennett 2013 wrote: “The Vienna specimen of Pterodactylus antiquus (Natural History Museum, Vienna 
specimen NHMW 1975/1756/0000) is complete, fully articulated, and preserves propatagial and brachiopatagial soft tissues on part and counterpart slabs. When first described, linear features in the patagia were interpreted as widely spaced cylindrical internal elastic actinofibrils present throughout the brachiopatagium, a projection into the suboval window framed by trailing edge behind the right elbow was interpreted as the result of bunching of actinofibrils originating at the carpus, and it was suggested that the appearance that the brachiopatagium attached to the distal femur might be misleading because Desmodus can present a similar appearance with wings folded at rest. The recent discovery of closely spaced broad flat keratinous actinofibrils and distinct fold lines in the wings of Rhamphorhynchus muensteri (e.g., Zittel wing, Marsh specimen) prompted a reevaluation of the Vienna specimen. It was found that linear features in the patagia include: 1) closely spaced broad flat structures subparallel to wing phalanges, lightly permineralized with calcite on the upper slab, interpreted as keratinous actinofibrils of folded dactylopatagium; 2) clumped straight structures originating behind the metacarpophalangeal joint and resisting longitudinal compression to project into the window on the right and a like distance behind the elbow on the left, interpreted as actinofibrils associated with fold A; and 3) often curving structures that parallel the leading edge of the propatagium and the trailing edge of the brachiopatagium medial to the window, interpreted as collagen fibers bearing tensile loads in tenopatagial patagia. The suggestions as to the appearance of trailing edge attachment to the thigh is accepted. The absence of uropatagial impressions indicates they were less resistant to decay than propatagia and plagiopatagia, probably because their tensile fibers were smaller and/or fewer. The new information permits a new reconstruction of Pterodactylus wings.”

Notes
Nice to get confirmation of the narrow chord wing membrane reconstruction with a fuselage fillet extending to the anterior thigh. As reported earlier, Peters (2002) followed Schaller (1985) and Zittel (1882) in presenting this interpretation and configuration as the ONLY true pterosaur wing membrane configuration — found in every known specimen, no exceptions.

Earlier we looked at Bennett’s reinterpretation of aktinofibrils as much wider structures. Now that they have been observed in two specimens the validity is enhanced. Even so, I would like to see an independent researcher confirm the observation. I’m still concerned about the “inextensibility” that Bennett mentioned, as the Vienna specimen shows how extensible the wings can be.

Surprised to see that Bennett thought the uropatagia were absent. Here’s a photo in visible light. Be sure to mouse over to see the interpretation of the outline. Below (Fig. 2) is another photo in visible light. A photo in UV light (Fig. 3) where the uropatagia appear to be missing because they don’t glow, but did leave boundary lines, just like the right propatagium.

Figure 3. The Vienna specimen in visible light. The uropatagia are indeed ephemeral.

Figure 3. The Vienna specimen in visible light. The uropatagia are indeed ephemeral.

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 2. 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. The uropatagia do not glow here.

References
Bennett S 2013. Reinterpretation of the wings of Pterodactylus antiquus based on the Vienna specimen. Journal of Vertebrate Paleontolgy abstracts 2013.
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Schaller D 1985. Wing Evolution. In: Hecht, M., Ostrom, J.H., Viohl, G. and Wellnhofer, P., eds, The Beginning of Birds. Proceedings of the International Archaeopteryx Conference, Eichstätt 1984, (Freundes Jura Museum, Eichstätt), 333–348.
Zittel KA 1882. Über Flugsaurier aus dem lithographischen Schiefer Bayerns. Palaeontographica 29: 7-80.

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