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Re: OCCAM'S RAZOR & THERIZINOSAURS



-----Original Message-----
From: Jonathon Woolf <jwoolf@erinet.com>
To: John V Jackson <jjackson@interalpha.co.uk>
Cc: dinosaur@usc.edu <dinosaur@usc.edu>
Date: 04 August 1998 03:10
Subject: Re: OCCAM'S RAZOR & THERIZINOSAURS


>John V Jackson wrote:
>
>> >> i):  Hair/fur originating as developments from reptilian scales much
>> along
>> >> the same lines as in pterosaurs and mammals, serving the joint
purposes
>> of
>> >> insulation, and drag for minimising fall damage and helping steerage
>> during
>> >> leaps.
>> >>
>> >> ii):  Simple hair structures becoming progressively more complex and
thus
>> >> increasing drag/weight ratio, eventually to the point where the
>> >> proto-feathers align horizontally when the creature is in flying
squirrel
>> >> pose.  With tail and arm feathers in this configuration, optimised to
>> oppose
>> >> downward movement, the capability to glide in simple table-mat style
>> would
>> >> smoothly and inevitably develop.  It is at this stage that aerodynamic
>> >> features of individual feathers would become subject to evolutionary
>> tuning.
>> >>
>> >> Note the tendency of feathers in flightless birds to move away from
fully
>> >> interlocking streamlined and sub-spatulate form, towards either
>> "explosive"
>> >> or longer and more hairlike forms, depending on usage.
>> >>
>> >> Um, I hope that helps.
>> >>
>> >
>> >It does.  Now the next question: if feathers evolved in either of the
ways
>> you
>> >describe, _before_ developing into an organ of flight,  [snip]
>>
>> I don't see how you could get that meaning from what I wrote!  Paragraphs
i
>> & ii are successive stages.
>
>Whichever.  The same question still applies: if feathers evolved this way,
then
>how do you justify the statement that the presence of feathers necessarily
>implies a flying ancestry?
>
>-- Jon W.


Partly from the tendency for ex-fliers to change the nature of their
feathers as I have suggested above, and partly due to the extreme
specialisation in their design.

JJ