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Re: Fw: Dinosaurs and birds
Thanks for the tip. This was one of my sources...
Ah, yes, I've read that post as well. Darren Naish is a really sharp
guy, and he writes very well, but I think he may have missed a couple
of items in that particular assessment. For starters, the The Crato
Formation azhdarchoid specimen SMNK Pal 3830 does not show much about
the patagium at all. If you look at an uncropped photo you'll see that
the section of patagium actually just passes under the hind limb
altogether. It is either just a completely detached piece of wing , or
it is a flipped section of uropatagium (which is what I think is going
That leaves the apparent phylogenetic bracket unbounded, such that we
have a few "rhamphorynchoids" like Sordes that seem to have broad
chords, and some others (like rhamphorynchids) seem to have quite
narrow chords. This leaves very little information about derived
pterodactyloids. I've actually talked to Darren about some pterosaur
mechanics, and I don't think he's actually particularly dead set on
wide chords for all pterosaurs (though he'd have to confirm that).
A few authors have found a correlation between forelimb and hind limb
lengths in pterosaurs, and suggested that this indicates a continuous
patagium. This is likely a constraint related to quadrapedal
terrestrial locomotion, instead.
The expected situation (at least from my point of view) is that the
planforms of pterosaurs would be efficient for their habitat and
associated flight dynamic, just as in modern flying animals. Species
in cluttered environments, or small bodied species that hunt insects,
would be expected to have wide chord wings. Pelagic species, which are
the vast majority of pterosaurs, would be much better served by high
aspect ratio wings and independent flight surfaces. Large-bodied
pterodactyloids, in general, would probably be most efficient with high
aspect ratio wings free of the hind limb, even those that lived inland.
There are a lot of common misunderstandings about flight dynamics,
especially soaring flight. I think some of these have heavily
influenced the preference for continuous flight surface models among
some pterosaur workers.