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On pterosaur wing development

July 16, 2013

So, with Mark Witton’s book out, and with my idea in restrospective failing on the account that warm blooded metabolisms would have probably been necessary prior to flight itself, I still have one thing to say about how pterosaurs went up in the air.

It seems very likely that gliding altogether was probably not how flight evolved in tetrapods, as bats seemingly began as flutters and early birds don’t seem particularly adapted for climbing. Pterosaurs, of course, coud had been the exception; after all, what else would motivate a glider to fly than the dry environments of the Triassic?

Nonetheless, in previous discussions, the idea that the wing finger actually began as a display device rather than something used for gliding has intrigued me. It would explain the unique wing finger retraction in pterosaurs – rather than an adaptation acquired to deal with progressively larger wing fingers, it would have predated flight as a way to keep the displaying membrane safe – and why flight would have evolved how it did: as the membrane expanded up the arm, the fifth finger, if still present, would be excluded and removed, and the presence of muscles in the membrane would have started since the very beginning, as means to expand and retract the signals in the membrane. It would also explain why pterosaurs took to the air so quickly: with such exadaptations, all you’d need would be extending the membrane along the body.


4 Comments leave one →
  1. July 17, 2013 12:43 am

    I got to start using that word exadaptation or is it exaptation? Anyways I always just said pre-adapted or co-opted when talking about anatomical features later reinvented for something else. It’s always refreshing to hear about alternative theories to the usual ground up or trees down theories of flight adaptation. Back around 2000 when we started to get all those feathered dinos I had my own pet theory that bird flight started underwater with theropods “flying” underwater after fish like auks/penguins. They then had an exaptation towards flight in the air. But I kind of gave up on this idea of mine since subsequent discoveries have not born my idea out.

    I do like the wing display idea- of course it could also work in a mosaic function with gliding happening too. We just need to see some of those proto-pterosaurs alas!!!

    • July 17, 2013 1:29 am

      No, its a quirk of mine. Exaptation is still the correct term.

      It sounds like a fun idea, that osrt of parallels the finned Compsognathus concept. Now we know early paravians were unambiguously terrestrial, but still…

      The sore lack of proto-pterosaurs is frustrating, but at least it offers interesting possibilities in the field of speculation.

      • July 21, 2013 1:14 pm

        Its not suprising giving how long ago they lived and how fragile their bones must have been. I bet If bats or birds evolved in the Triassic we would be just as in the dark on their origins as pterosaurs.

      • July 21, 2013 3:59 pm

        True – and we still know very little about how bats got into the air anyways, as like pterosaurs they too lack conclusive “missing links”

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