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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.

Cheers,

--Mike


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181