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Re: Screaming dromaeosaur biplane killers of the air

HP Tim Williams asserted:
If one hypothesizes that birds evolved from _Microraptor_-like ancestors,
then a similar pathway would be invoked: Four-limbed glider to two-limbed
flier.  Unlike pterosaurs, the "protobirds" show a discontinuous gliding
surface, making it much easier to decouple the hindlimbs from the flight
surface.  This implies the absence of hindlimb feathers in _Archaeopteryx_
and other primitive birds is secondary - if you don't use 'em, lose 'em.

Are you sure that you want to include the 'use it or lose it' principle?
There goes retention of neutral mutations, among other problems.
One easy adjustment would be that the cost of maintaining feathers was too
great when those hindlimb feathers had no flight role.
Just wondering.