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On Thu, 29 Aug 1996, Jerry D. Harris wrote:
> BTW, this message also serves as a test message; has this list been
> dead of late, or is it just me???
Sure seems that way. I actually have a couple questions I've been
wondering about... one of them is that I recently saw a structure in
nature that is the only thing I can think of that paralells the evolution
of feathers. It serves an aerodynamic, rather than insulatory, purpose,
and someone has told me that these little tufts of down are from the
thistle plant. The actual structure of each "plume" is a central shaft
with secondary hairs branching off, it vaguely resembles the ratite
feathers. The thistle down implies to me that even a
relatively simple, ratite-like feather might have some serious aerodynamic
advantages over simple hairs. On the subject of feathers, I'm surprised
no one ventured to speculate where the one in the AMNH's natural history
exhibit (a ratite-like plume in Cretaceous amber) might have come from,
if not from a bird.
I've also heard something to the effect that conifers would have
been severely vulnerable to being fed upon by dinosaurs, because they
only put out needles once a year, but yesterday I noticed that on a
Metasequoia there was what appeared to be new growth coming out. So is
putting out growth only once a year a specialization of modern conifers
(perhaps it has something to do with their generally high-latitude
distribution?) or the primitive condition which Metasequoia appears to
have evolved away from?
And these duckbills and ceratopians simply beg the question, yet
again, why did dinosaurs get so large? Obviously, the environment has to
select for it. But does the environment no longer select for these kinds
of giants, or is there simply nothing today living that can respond to
such selectional pressures the way dinosaurs did?