Azhdarchids: more like storks? or more like ground hornbills?

Figure 1. A selection of wading storks. With their long necks and long legs, these waders seem to resemble little azhdarchids.

Figure 1. A selection of wading storks. With their long necks and long legs, these waders seem to resemble little azhdarchids as seen in figure 3.

Witton and Naish (2008) continue to insist that long-legged azhdarchids (Fig. 3) were more like short-legged ground hornbills (Fig. 2), down to their terrestrial stalking habitat and diet. A minor back and forth has started to brew in their PLoS comments section.

I still think there’s still a case to be made for azhdarchids more like modern storks and herons (Fig. 1), including a wading habitat and diet.

Here are a few images for direct comparison.
I think ground hornbills can be more accurately compared to Germanodactylus (Fig. 2) than any azhdarchid. Agree? Not sure why Witton and Naish (2008) overlooked this rather obvious match, other than playing favorites with azhdarchids for their grandeur and the possibility of wolfing down baby sauropods.

Is it even possible to compare birds and pterosaurs? Perhaps not. But you won’t win any bar bets either way as both sides of this argument are firmly entrenched. So each of you will have to decide how you “feel” about this…

Figure 1. Click to enlarge. Ground hornbills compared to a Germanodactylus, JME Moe-12.

Figure 2. Click to enlarge. Ground hornbills compared to a Germanodactylus, JME Moe-12. Ground hornbills are more like mega-crows than storks. The long legs and long neck of azhdarchids is not duplicated in ground hornbills.

Webbed feet?
Witton and Naish also thought that pterosaur waders would need large webbed feet. While that makes perfect sense, it’s not true among living birds. For instance, the wading stilts have small slender toes without webbing, falsifying their assumption. Witton and Naish thought that the spreading toes in the stilt bird made all the difference. However, known wading pterosaurs, like Pterodaustro, also lack webbing (it has not been preserved) and have parallel toes leaving little room for webbing in any case, similar to azhdarchids.

Figure 3. Mark Witton's version of a large Quetzalcoatlus at 5 m tall, next to a giraffe and 6 foot tall human. On the right are a selection of azhdarchids to the same scale from reptile evolution.com.

Figure 3. Click to enlarge. On the left, Mark Witton’s version of a large Quetzalcoatlus at 5 m tall, next to a giraffe and 6 foot tall human. On the right are a selection of azhdarchids to the same scale from reptile evolution.com. Please ignore the wing membrane connection to the shin on the Witton reconstruction. It is an error that Witton continues to promote. It is noteworthy that azhdarchids have heron-like proportions and likely a similar wading lifestyle.

We looked at azhdarchid wading postures and the evolution of gigantic size earlier here. We looked at the potentially largest azhdarchid, Hatzegopteryx (Fig. 3), here.

References
Witton MP and Naish D 2008. A Reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271

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