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Re: 11th specimen of Archaeopteryx
On Oct 27, 2011, at 10:54 AM, Don Ohmes wrote:
> Well, in general, yes -- it is just that a plausible specific behavior
> or lifestyle that incrementally takes a skeleton from limited upstroke
> (as ascribed to Arch. by some) to powered flight w/out going through a
> gravity-powered phase has not been advanced.
I suppose that's true enough, but at the same time I don't tend to have much
confidence in particularly specific behavior or lifestyle scenario building. I
know that paleontology has a long history of fun scenario building. I am not a
fan, however. More general categories is probably all we can really ascribe.
So, for example, any of terrestrial control-based models would seem to fit the
bill, even if they don't give a particularly specific scenario set.
> One weak point is that the above mentioned non-flight-related
> pre-powered-flight behaviors don't provide a clear path to evolution of
> brain/nervous system control mechanisms.
Actually, that might not be a big deal - the neural control required for
complex terrestrial and/or arboreal locomotion might actually be sufficient for
basic flight control. Flight is not necessarily more control-hungry than
running, leaping, and climbing. Particularly maneuverable flight probably is,
but not just staying in the air with basic obstacle avoidance.
> Or, to re-state -- if control surfaces and asymmetrical primaries appear
> prior to a full up-stroke, the more parsimonious path to flight is NOT
> 'ground-up' or 'active' or whatever the latest term is...
I don't know which is more parsimonious, though that might not be terribly
important in this case, anyway. However, control surfaces could be used on the
ground without a full upstroke - affecting angle of turn, for example, does not
require exceptional abduction.
I'm not necessarily arguing for a terrestrially-based flight origin, but I
don't think it's clear that it is immediately less plausible.
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