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Re: Did Feathers Evolve for Dispaly? We Still Don't Know! (unCHOP!ed version)



Michael Erickson <tehdinomahn@live.com> wrote:

> Hence the title of my post - did feathers evolve for
> display? Maybe. Maybe not. (My own personal opinion is
> 'not', but that digresses, and matters little anyway.) The
> point is that the hypothesis that feathers initially evolved
> as display devices is really no more robust today than it
> was yesterday, or the day before that, or the day before
> that.


Yes, the paper by Zhang et al. is a great deal more guarded on this point, and 
essentially leaves the question hanging...


"As the melanosomes are preserved in life position in the Jehol fossils,
detailed study of differences in their spatial distribution, including
orientation and density, and the relative abundance of each type, will
reveal greater detail regarding both colour and colour patterning.
Reconstruction of colour patterns will also inform debates on the functions of 
feathers in non-avian dinosaurs, whether primarily for
thermoregulation, camouflage or communication."


Most of the paper is devoted to description of the melanosomes, and why the 
authors believe they are genuine melanosomes and not artifacts.  The biology of 
the animals themselves is only mentioned in the last paragraph, and speculation 
(such as what the coloration was actually used for in the animal) is kept to a 
minimum.  The latter is probably driven by the need for brevity.  This is a 
Nature paper, after all.


However, the news story you mention does address the issue of why 
display/communication is preferred over thermoregulation as a reason for the 
inception of feathers (and like you, I'm including 'protofeathers' under this 
heading).  Quoting Benton directly from the article:


"Furthermore, we now know that the simplest feathers in dinosaurs such as 
_Sinosauropteryx_ were only present over limited parts of its body â for 
example, as a crest down the midline of the back and round the tail â and so 
they would have had only a limited function in thermoregulation."


So if most of the animal remained 'naked', then the fea
t and help keep it warm.  I actually like this idea of display being the 
original function of feathers.  For example, imagine if huge eye-spots were 
found on the inside wings of _Microraptor_!


Cheers

Tim