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Re: "running" elephants - locomotary analoges
Jaime A. Headden wrote:
> But could this scenario not lead one easily to indicate that these "flight
> characters are evidence of regressiong of flight ability inversely
> proportional to increasing size? One could easily offer this in many
> birds, for instance many galliforms seem to follow this trend. Or among
> the heavier parrots, the kakapo comes to mind. Why would having a
> "obviously flight worthy" wing mean it could actually fly or do so well?
A 'flight worthy' wing, would need to be taken in the context of the
animal it is supporting. The 'power required' vs. 'power available'
relationship in flying animals does exist, but as usually stated, it
incorrectly presumes that the wing shape remains pretty much unchanged
as size increases and that power production techniques do not vary
substantially with increasing size -- which leads to artificial size
constraints. In life, if flight is to be maintained, the wing shape as
well as the size needs to be adapted acordingly, and provision needs to
be made to accomodate the 'power available' scenario. In large
azhdarchids the humerus shape seems to be a limiting feature for maximum
wingspan in cruising flight, and the two extant humeri (is that the
correct plural?) of the really big azhdarchids do not appear to have
been morphed to the maximum limit. If that were the only limiting
factor, we could expect that there might be some bigger beasties still
to be found, but it isn't the only limiting factor. The big azhdarchids
do not appear to have had enough muscle mass to launch by flapping or by
running and flapping, but they do appear to have had more than enough
muscle mass to launch quite handily using another technique. So the
largest known pterosaurs haven't reached the launch limit either. Again,
we could expect that bigger beasts may still be there to be found.
Though I'd get edgey if someone reported a wingspan more than about 13
meters for some new pterosaur unless they explained some of the
structural and power production techniques such an animal might be using
to compensate for the increased mass.
> The application of Jim Cunningham's data may only show an evolutionary
> novelty from an originally well-functioning flight wing in smaller,
> less-advanced azhdarchids.
I'm sorry, I'm not following your intent. Please elaborate? As an
aside, decreased size does not imply a less advanced condition, nor does
increased size imply a more advanced condition.
> This does not mean the data is wrong.
> Just different from a method of incomparable position.
Again, I'm not following..... Not disagreeing either - I just don't know
what you are saying. Again, if you would elaborate a bit?
> John has been
> very careful in presenting the exact data used to reach his conclusions,
> it is this data that should be investigated, not anecdotes.
I sort of agree, but anecdotal information can be used to set up
scenarios, and the data used to see if those scenarios are possible, or
if the scenarios are known to be possible, then one can search for flaws
in either the data or the way it is applied. That said, I have no idea
whether John is correct or not. Or Greg.