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Re: How did dromaeosaurs use their arms?



In a message dated 5/10/00 3:45:42 PM EST, ptnorton@email.msn.com writes:

<< Research has shown that feathers, even simple covert-type feathers, 
significantly decrease aerodynamic drag over a surface.  That's a significant 
aerodynamic effect which is not just relevant for flight but also for ground 
based manueverability. >>

I can think of no extant cursorial animals whatsoever that have featherlike 
or hairlike forelimb structures for ground-based maneuverability that didn't 
already have them because they're descended from flying ancestors--and such 
forelimb structures are usually vestigialized. Simply using the feet against 
the substrate is >far!< more effective for ground-based maneuverability than 
any kind of aerodynamic integumentary structures or forearm flailing. 
Hypothesis rejected: is awkward, doomed attempt to figure out >some kind< of 
farfetched way that feathers might have appeared in ground-dwelling cursors 
without having them simply go up into the trees and fly/glide first.