Re: Tar and feathers

["Tim Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic <david.marjanovic@gmx.at> wrote:

> The Berlin specimen of *Archaeopteryx* still has impressions of contour 
> feathers on both sides of the left lower leg. Get a photo and look. I do 
> not understand why it was once claimed that *A.* lacked or could have 
> lacked feathers except for remiges & rectrices.

The controversy surrounding the disposition of feathers in _Archaeopteryx_ 
concerns not so much whether it has contour feathers or not, but whether it 
had tertials.  Tertials are the "inner wing" feathers, and their presence 
governs the proximal extent of the wing.  Considering the length of the 
humerus in _Archaeopteryx_, the absence of tertials would create a big gap 
in the wing.  The presence/absence of tertials has ramifications for flight 
in _Archaeopteryx_ and, ergo, for the evolution of avian flight.

> We know that adult *Carnotaurus* did not have feathers over most of
> their bodies.

I'm glad you specifed *adult* _Carnotaurus_.  I'm confident that the 
presence of feathers in at least some dinosaur taxa will one day be shown to 
have an ontogenetic component.  One hypothesis is that feathers began as 
downy structures in baby dinos and were retained (by neoteny) in taxa that 
achieved only a small adult body size (e.g., maniraptoriforms) and those 
that lived in polar regions (e.g., Australo-Antarctican ornithopods, as 
mentioned previously).



Tim


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