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Re: Disney's Dinosaur Trailer

BettyC wrote:

>probably walking quadrepedally?<

Perhaps so.  Betty's idea that those muscles may be related to terrestrial
locomotion is interesting. I hadn't even considered that, but it's worth
thinking about. Birds don't use their wings for terrestrial locomotion, and
bats generally don't, but a flying vertebrate that was also a frequent
quadrapedal walker might show some neat differences.

My basic point is that evolution would be strongly selective towards
minimizing mass in the distal forelimb elements of flying vertebrates, for
obvious biomechanical reasons. So anytime we see isolated concentrations of
mass in distal limb elements (such as avian wing muscles), we need to look
for a very important functional explanation.  We don't see such mass in bat
wings (not much, anyway). We do see it in birds, but in my opinion--and this
is what led to my original question-- the evolutionary rationale offered by
researchers for maintaining that condition seems weak.

I'll leave it to others to present evidence of wing muscles (or wing-like
muscles) in pterosaurs and to offer an explanation of their function.


>The bat* walks with it's 'inner wrist' (about where the base of the
>fleshy part of a human hand meets our wrist, towards the base of the
>thumb) as the contact that touches the ground during it's quadrapedal
>walk. I suspect the 'wrist' is probably kept at tension (in one
>position) throughout a stride length.  This may be simply that there is
>very little muscle to move the wrist OUT of this position during a
>stride length... but since wrists function as a joint of rotation for
>all points PAST it towards the ends of the fingers, well, if you press a
>rotating joint to the ground it can't bend.
>Pterosaurs left full manus impressions of their 'hands'.  This means
>that the wrist is above the point of contact with the ground and this
>probably preserved flexibility of the wrist.  I'm not saying that
>pterosaurs had to flex their wrists during a stride length but they
>could.  Since the movement is possible, perhaps these inner wing muscles
>controlled wrist flexion during a walk?
>-Betty Cunningham
>*some bats may walk on the pad that would be equivalent to the webbing
>between the thumb and forefinger of a human hand (towards the thumb more
>than towards the finger)
>Pat and Jim said:
>> Bats have much less massive wing muscles (relatively) than birds, and I
>> admit to assuming that pterosaurs did as well.  If pterosaurs had massive
>> wing muscles (again, not "flight" muscles) I'd be interested in knowing
>> they were used for.
>> > We are talking about the inner wing here, inboard of the wrist<
>> I was talking about wing muscles.
>> >not the outer wing which was mostly (but not entirely) tendon and
>> membrane.<
>Flying Goat Graphics
>(Society of Vertebrate Paleontology member)