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Re: Re.: If Dinosaurs Could Fly and an old 'axiom'



At 08:20 AM 21/01/1998 -0600, you wrote:
>
>>The following is taken from the article "feather" in "A Dictionary of
Birds":
>
>What's their source? 

The articles in the Dictionary are all written by experts (well, nearly
all; I wrote a few myself).  This article was a revision by Jan Dyck of the
University of Copenhagen of an original by Prof. P.G. 'Espinasse.  It cites
general references only, including the classic "Avian anatomy. Integument"
by Lucas and Stettenheim (1972).

>So the feather is primarily a dermal, not epidermal, structure?  Makes sense.

It seems to be a combination of the two, but of course the epidermis can
itself be viewed in part as a product of the dermis.

>Sheaths are retained on the pygostyle (tail), no?  Sounds like a double
>cylinder might be the primitive condition.

No; all developing feathers ("pin feathers) shed their sheaths as the
faethers mature, to my knowledge.

>
>>"The inner aspect of the lengthening cylinder becomes longitudinally
>>pleated or ridged.  
>
>Let me be the first to say that I'm not clear what this means.  "Inner
>aspect" meaning the developing rachis as opposed to the sheath, or the
>reverse side of the rachis?  "Longitudinal" meaning the ridges run
>length-wise along the rachis, or circumferentially around it? 
>
>>These ridges contain the developing barbs.  Within the
>>substance of the barb-ridges many cells fall away individually and take no
>>part in the structure of the finished feather, but some become firmly
>>joined to each other and form the rami of the barbs.  Other cells become
>>joined in columns, each column sloping downwards towards its barb, to which
>>proximally it becomes firmly fixed.  
>
>I apologize for being thick, but I don't understand this either.  Does this
>mean that the ridges cells form the barbs before the ramus develops to any
>extent, attach to the ramus and sort of unfold from the ridges as the ramus
>grows outward?
>
>Several helpful people have tried, with only marginal success, to improve my
>feather terminology.  If I'm still getting it wrong, please let me know.
>
>  --Toby White
>
>
>
>
>
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net