Re: If Dinosaurs Could Fly

["Matthew Troutman" <m_troutman@hotmail.com>]

>>I think you're missing the point.  Not all feathers serve an 
insulatory
>>function.  In modern birds insulatory feathers are down feathers, not
>>flight/contour feathers.  Down feathers are highly derived feathers.
> 
>
>This is not to say, though, that contour feathers can have no 
insulating
>function.  More to the point, it says nothing about the insulating
>properties of "protofeathers", if that is what the structures on
>Sinosauropteryx really are.  And it avoids other possible uses of body
>feathers such as display.

      The only true insulatory feathers are the degenerate ( lacking 
derived barblets) of ratites and flightless birds. Down is not an 
effective insulator in wet conditions. One of the main causes of infant 
mortality in juvenile birds is when the down feathers get wet and they 
die of hypothermia. Pretty maladaptive.

>>  The
>>feathers from which down feathers are derived functioned in flight, 
not
>>insulation. 
>
>There is simply no hard evidence of which I am aware to support this
>statement.  Frankly, we do not know whether contour and down feathers 
(as
>well as bristles, filoplumes and other feather types) evolved from 
flight
>feathers, or all of these evolved from an ancestral type (which might 
have
>been the Sinosauropteryx-type protofeather).  

     Down feathers and filoplumes can be traced to contour feathers 
quite easily. And as stated above down as insulation is maladaptive.


>There is a logical evolutionary progression
>>from scales (in ectothemic avian ancestors) to flight/contour feathers 
(in
>>ectothermic early birds) and finally to downy feathers (in later, 
enothermic
>>[ornithurine] birds). 
>
>I know of no evidence on the appearance of down; for all we know
>Archeopteryx could have been buried in the stuff, but it just didn't
>fossilize.  

See above.

There may be a speculative evolutionary progression, but when
>it comes to the facts we come up pretty short.  In fact I do not thik 
the
>progression you propose is "logical" at all - it seems supremely 
illogical,
>evolutionarily and/or developmentally speaking, to assume that a highly
>specialized integumentary structure would develop to a considerable 
degree
>of refinement on one part of the body and then (and only then) be 
modified
>for a different function on other parts of the body.  If Currie is 
right
>about his interpretation of Protoarchaeopteryx, the evidence is that 
more
>than one type of featherlike structure could be present simultaneously 
on
>even a creature well down on the bird family tree (whether or not its
>features correspond to those on Archaeopteryx's true ancestor, whatever
>that was).

     I agree here. There must be in essence a " pre-contour/flight 
feather".

 WMattTroutman

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