Re: FLIGHT & CATS

["Tim Williams" <tijawi@hotmail.com>]

Mark the illustrator (SNOWFL96@aol.com) wrote:

> I think the tree-down version is much more correct. There is so much proof
> for this theory like... flying snakes, squirrels, frogs, marsupials, and of
> course, lizards.


I would agree that the "trees-down" scenario is more likely than a 
"ground-up" for the evolution of avian flight, but for different reasons 
than the one above.

The above list of parachuting or gliding vertebrates (and there are many 
more)emphasizes the prevalence of aerial locomotion among arboreal 
vertebrates in order to get from tree to tree (or from branch to branch, or 
from a tree to somewhere else...).  For example, skin membranes (patagia) 
supported by the fore- and hindlimbs and designed for aerial gliding evolved 
probably more than half-a-dozen times in mammals alone.

*But*, there is no compulsion to believe that birds passed through such a 
passive gliding stage.  I would argue (and have argued) that birds did not.  
Remember, all the above critters are quadrupeds (except for "flying" snakes, 
of course).  Birds are bipeds, and I have no doubt their immediate ancestors 
were as well.

The suite of anatomical features (integumental and osteological) present in 
those theropod taxa closest to the origin of birds, and ecomorphological 
interpretations of these characters, leads me to favor a gravity-assisted, 
facultatively arboreal ("trees-down") origin of flight in birds.

Plus, the idea of small maniraptorans leaping from trees is pretty darn 
cool, IMHO.


Tim


>


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