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Re: Lemurs and Feathers



In a message dated 6/19/01 5:20:50 PM, ptnorton@msn.com writes:
<< One thing I like about the brooding hypothesis is that it provides a 
non-aerodynamic explanation for the evolution of elongated, vaned feathers on 
the back-side of the arms. As such large flat surface areas evolved, however, 
aerodynamic forces would be an increasingly signficant factor in selecting 
modifications that anchored those feathers more firmly to the musculoskeltal 
structure of the animal. As that began to happen, the arm would begin to 
function more like a wing in that it would be capable of using arm motions to 
generate lifting, thrusting and braking forces. >>

Mark Orsen and I are including a long list of such forces in our new 
manuscript on the subject. Also, Ostrom had a few such observations in his 
original 1969 article. Imagine macroraptor in a wind storm, and you will 
begin to see all kinds of reasons for stiffening feathers and adding 
musculoskeletal modifications for their control and management. Now, if those 
feathers are critical for covering the young, voila! you have a selective 
pressure to drive the development of a wing-like structure in the absence of 
flight.

Thomas P. Hopp
Author of DINOSAUR WARS, a science fiction novel published by iUniverse
Now Humans are the Endangered Species!  http://members.aol.com/dinosaurwars