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Re: FEATHERS



At 05:00 PM 10/6/96 -0500, Dinogeorge wrote:

>Of course, the answer to this is that ANY kind of hairlike or featherlike
>dermal structure would almost automatically be "wonderfully adapted for
>insulation" if it simply covers the skin densely enough. The problem is not

        Yes, but feathers, with their intricate rebranching structure are
better insulators than "ANY kind of hairlike dermal structures", am I
correct PG?  I recall that this was an important example in material science
of what makes a good insulator.  Like wool, they lengthen the path that heat
must travel, as the analogy goes, and thereby lessen the heat loss.  They
are prabably more effective at trapping air against the body, but I will
leave this up to PG to address.  In any case, while feathers are unique
structures, well adapted for flight, they are also very well adapted to
insulation, probably more so than our hair.  I do not think it is too much
to say that they are "wonderfully adapted for insulation".

>understanding the evolution of insulation; the problem is understanding
>specifically the evolution of structured feathers. This is where the BADD
>theory goes _ad hoc_ on us.

        As if evolution does not *always* go ad hoc?  Or are your arms still
planning on turning into wings, senor Olshevsky?  ;)

>But the main question is, Did avian ancestors REQUIRE insulation? That is,

        It is far simpler to demonstrate that they had it or did not.  Yes,
I am aware of the irony...

>were they endothermic? It has begun to look as if avian ancestors (and other
>dinosaurs) were active >ectotherms<, not endotherms after all. If this turns

        I would disaggree, oh jumper-on of bandwagons.  We simply have a
debate once again.  Perhaps we accepted this as a foregone conclusion before
all the facts were in, but I certainly wouldn't go throwing in the towel on
turbo t-rex just yet.  We have one strong correlation (respiratory
turbinates), and a couple of good theories.  Against that evidence, we have
a profusion of evidence that dinosaurs were active creatures, and some
decent arguments as well.  It hardly looks like there is a conclusion in sight.

        Wagner
+--------------------------------------------------------------------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
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