“Pterosaurs” (2012) – same old problems – but gorgeous!

Veldmeijer, Witton and Nieuwland (2012) have a relatively new book out (Fig. 1, well… it just recently came to my attention), “Pterosaurs, Flying Contemporaries of the Dinosaurs.” And, like Witton (2013), this book presents the same problems in a gorgeous and easy-to-read fashion.

Figure 1. Pterosaurs, Flying Contemporaries by Veldmeijer et al. 2014.

Figure 1. Pterosaurs, Flying Contemporaries by Veldmeijer et al. 2014. Gorgeous artwork, unfortunately flawed by adherence to deep chord wing membranes. (See figure 4). This is akin to having dinosaurs continue to drag their tails in 2014.

Just a few pages will suffice for this review, but the whole book is available online here.

Problem # 1.
The authors nest pterosaurs between plesiosaurs and crocodiles (Fig. 2). Folks, I’m not making this up, but I think they are. Certainly this is the result of a dartboard throw, because no comprehensive phylogenetic analysis would ever produce these results. Rather, you can find the tested and verified nesting of pterosaurs here at the large reptile tree.

Figure 2. Veldmeijer et al. family tree nests pterosaurs between crocs and plesiosaurs, breaking all past traditions and barriers.

Figure 2. Veldmeijer et al. family tree nests pterosaurs between crocs and plesiosaurs, breaking all past traditions and barriers. Type enlarged for legibility. Color added.

Problem #2
What Bennett 2006 identified as a baby Germanodactylus, Veldmeijer et al. identify as a baby Pterodactylus (Fig 3). When we get back to reality, phylogenetic analysis nests it is as an adult of its own genus and clade, not even in the lineage of either more widely known genus. The little one is  SoS 4593 (formerly PTHE No. 29 III 1950, No. 9 of Wellnhofer (1970). If it looks like a little Scaphognathus, that’s because it is derived from little scaphognathids that were likewise reducing the tail. Bennett, Witton, Veldmeijer all have bought into the hypothesis of allometry (morphological change) during ontogeny, ignoring the proof for isometry during ontogeny in pterosaurs in Zhejiangopterus and embryo pterosaurs, like Pterodaustro.

Figure 3. Not a baby Pterodactylus, but a full grown tiny pterosaur the size of a sparrow.

Figure 3. Not a baby Pterodactylus, but a full grown tiny pterosaur the size of a sparrow. Insert added to put the two images to the same scale. One key to telling these two apart is in the feet. They had distinct phalangeal proportions unlikely to change during ontogeny. Plus, we have families of pterosaurs that demonstrate isometry during ontogeny. And these have been known for decades now. 

Problem #3
Sadly, like a droopy dinosaur tail, these pterosaurs (Fig. 4) continue to have bat-like, deep chord wing membranes, for which there is no evidence whatsoever. All the evidence proves that pterosaurs had a narrow chord wing membrane, like the added insets show.

Figure 4. Glamour shot of flying azhdarchids, unfortunately with deep chord wing membranes.

Figure 4. Glamour shot of flying azhdarchids, unfortunately with deep chord wing membranes. Insets offer corrections.

Problem #4
Finally, the authors offer a tracing from Wellnhofer 1991, of a quadrupedal walking pterosaur. I often like to place the trackmaker into the tracks (not in front of them  – Fig. 5) to see how carefully the artist has drawn the match. In the lower drawing, note the width of the track does not match the length. On another aspect going back to the original drawing, It’s best, when trying to match trackmakers to tracks, to elevate at least one or two and maybe three of the feet, leaving only one planted, not all four, as shown here (Fig. 5). When all four are implanted the animal has stopped. When two limbs are raised it is in the process of making tracks.

Figure 5. Above, standing/walking pterosaur traced from Wellnhofer 1991 by Veldmeijer et al. . Below, problems are illuminated. If you're going to have deep chord wing membranes, then you can't switch back to narrow chord ones when you want to. Rather, if you're going to be true to a configuration, then let the membranes droop when they're not pulled taut by the hind limbs.

Figure 5. Above, standing/walking pterosaur traced from Wellnhofer 1991 by Veldmeijer et al. . Below, problems are illuminated. If you’re going to have deep chord wing membranes, then you can’t switch back to narrow chord ones when you want to. Rather, if you’re going to be true to a configuration, then let the membranes droop when they’re not pulled taut by the hind limbs. And note the width of the track does not match the length.

It’s also valuable to animate the walk in order to work out all the problems. In figure 5, for instance, it is difficult to see how such a crouched over pterosaur could make such a long stride. It’s also difficult to imagine the order of limb placement.

Pterodactylus walk matched to tracks according to Peters

Figure 6. Click to animate. Plantigrade and quadrupedal Pterodactylus walk matched to tracks

If Veldmeijer et al. had just taken the time to match a real pterosaur to a real track they would have found what I found, that the only way to make it work is to elevate the back bone, as in this animated trackmaker that fits every step (Fig. 6).

References
Veldmeijer AJ, Witton M and Nieuwland I 2012. Pterosaurs, flying contemporaries of the dinosaurs. online here.

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