Pterosaur wing appearance when quadrupedal

Figure 1. GIF animation (2 frames) showing the original and repaired versions of this Quetzalcoatlus statue and its artisans.

Figure 1. GIF animation (2 frames) showing the original and repaired versions of this Quetzalcoatlus statue and its artisans. Pterosaur wings folded to near invisibility when folded as shown by manipulating bones and observing fossils. Only a narrow chord wing membrane, as in figure 2, works here. Note the unwarranted wrinkles in the original wing membrane. Note in the original the trailing edge of the wing membrane is directed to mid-metacarpal, rather than to the 180º metacarpophalangeal joint as in the repaired version, fossils and other illustrations below. And what is going on with those tiny anterior pteroids? That is wrong, so wrong.

Pterosaur workers
artists and filmmakers have struggled to portray pterosaur wing membrane when the wings are folded and the pterosaur is walking around (Figs. 1, 3–5). Fossils (Fig. 2) that show how the wings looked when folded are too often ignored.

Figure 4. Here's how the wing membrane in pterosaurs virtually disappeared when folded. This is CM 11426 (no. 44 in the Wellnhofer 1970 catalog),

Figure 2. Here’s how the wing membrane in pterosaurs virtually disappeared when folded. This is CM 11426 (no. 44 in the Wellnhofer 1970 catalog), Note: the left wing has been axially rotated during taphoonmy such that the folded portion of the membrane was fossilized posterior to the bony spar.

CM11426
(Fig. 2) shows how wing membranes fold down whenever the wing bones are flexed (folded). Like bats, pterosaur wing membranes fold away to near invisibility. If you think CM11426 looks a bit like Quetzalcoatlus, you’re right! It’s in the lineage in the large pterosaur tree (LPT), but it’s not larger than a typical Pterodactylus (Fig. 9).

Stan Winston Pteranodon suit for Jurassic Park 3.

Figure 3. Stan Winston Pteranodon suit for Jurassic Park 3. Those wrinkled wing membranes are a dead giveaway that Winston was lost when it came to wing folding in Pteranodon. And that’s not to mention the too short metacarpals (see fig. 4 for comparison)

For Jurassic Park 3
Stan Winston’s Pteranodon (Fig. 3) had saggy, baggy wing membranes. So did early paintings by Burian (Fig. 4). These clearly do not reflect what happens in fossils and in life.

Figure 4. Artist Z. Burian also struggled to realistically portray the folded wing membrane in pterosaurs forgetting the fossils and the fact that both birds and bats have no trouble folding their wings without wrinkling them.

Figure 4. Artist Z. Burian also struggled to realistically portray the folded wing membrane in pterosaurs forgetting the fossils and the fact that both birds and bats have no trouble folding their wings without wrinkling them.

Too often 
artists freehand their pterosaurs (Fig 5 purple), ignoring the bone and soft tissue evidence.

wo of the most completely known Pteranodon

Figure 4. Two of the most completely known Pteranodon (UALVP24238 and NMC4138) along with the skull of KUVP2212 to scale. In purple, John Conway’s Pteranodon (purple) with a much smaller skull and an inappropriate  elbow-high walking configuration.

Toy Pteranodon, ca. 1962, from the Marx Company.

Figure 5. Toy Pteranodon, ca. 1962, from the Marx Company.

Toy pterosaurs
also suffer from deep chord wing membranes (Fig. 5). Proportions here are wildly inaccurate for the toddler set. Accuracy is also absent in many professional reconstructions that include skeletons (Fig. 4), so there is enough blame to go around. The fossils (Fig. 6) document how the artists and sculptors should present those folded wing membranes. Too few artists and sculptors who claim accuracy are actually producing accuracy.

Figure 1. Click to enlarge. The plate and counter plate of the BSP AS V 29a/b specimen of Pterodactylus with color overlays of the bones and visible soft tissues.

Figure 6. The plate and counter plate of the BSP AS V 29a/b specimen of Pterodactylus with color overlays of the bones and visible soft tissues.

What do you get when you choose accuracy?
A much less monstrous awkward portrayal and a much more elegant bird-like/bat-like portrayal comes from keeping true to the bones and soft tissues as they are. Deep chord wing membranes that attach to pterosaur ankles are as outdated as tail-dragging dinosaur portrayals. And while we’re at it, keep those pteroids pointing inward, forming straight leading edges for the distal propatagia.

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.

Figure 7. 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.

Pterodactylus walk matched to tracks according to Peters

Figure 8. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

This animation frame (Fig. 7) from a walking pterosaur movie associated with the Crayssac tracks accurately portrays the wing membrane essentially invisible when folded. Artist unknown.

Another animation matched to Crayssac tracks (Fig. 8) does not include wing membranes, but they would have been nearly invisible here. This version shows a more upright quadrupedal stance, as if the pterosaur wings were used like ski poles. As noted earlier, this is essentially a bipedal pose, enabling wing opening and flapping without shifting the center of balance.

Go with the evidence, not traditional and sometimes current renderings. Follow the evidence.

The Vienna Pterodactylus.

Figure 9. The Vienna Pterodactylus.  Wing membranes in situ (when folded) then animated to extend them. There is no shrinkage here or in ANY pterosaur wing membrane. That is only an “explanation” to avoid dealing with the hard evidence here and elsewhere.

While we’re talking about Quetzalcoatlus
and its flying abilities, it is worthwhile to take another look at gracile m4.2 (second wing phalanx) on the giant Q. northropi vs. the same phalanx on the much smaller and more likely volant Q. species (Fig. 10). Sorry I didn’t bring this up during the earlier discussion, on azhdarchid flight, first published online three years ago here, but I forgot I had it, and it’s more damning evidence against giant pterosaur flight.

Figure 1 Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn't make sense if Q. northropi was volant.

Figure 10. Quetzalcoatlus sp. compared to the large specimen wing, here reduced. I lengthened the unknown metacarpus to match the Q. sp. and other azhdarchid metacarpi. I offer the wing finger has reconstructed by the Langson lab and with filler reduced. Note m4.2 is narrower on the larger specimen, which doesn’t make sense if Q. northropi was volant.

Figure 1. Freehand wing planform cartoon for Quetzalcoatlus from Witton and Habib 2010. There is no evidence in any pterosaur for this wing plan.

Figure 11. Freehand wing planform cartoon for Quetzalcoatlus from Witton and Habib 2010. There is no evidence in any pterosaur for this wing plan. Such deep chord wings cannot help but create unwarranted wrinkles when folded.

Wing folding
and the muscles that enabled complete flexion (Fig. 12) were covered earlier here.

Figure 1. Pterosaur (Santanadactylus) wing folding. Note when the wing is perpendicular to the metacarpus the flexor must be off axis in order to complete the wing folding process. The insertion must be distal to the joint because the flexor process of m4.1 extends dorsally over the metacarpus during wing folding. Otherwise the ventral (palmar) flexor would be cut off from the swinging dorsal process.

Figure 12. Pterosaur (Santanadactylus) wing folding. Note when the wing is perpendicular to the metacarpus the flexor must be off axis in order to complete the wing folding process. The insertion must be distal to the joint because the flexor process of m4.1 extends dorsally over the metacarpus during wing folding. Otherwise the ventral (palmar) flexor would be cut off from the swinging dorsal process.

References
Witton MP and Habib MB 2010.
On the size and flight diversity of giant pterosaurs, the use of birds as pterosaur analogues and comments on pterosaur flightlessness. PlosOne 5(11): e13982. doi:10.1371/journal.pone.0013982

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