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Long - Endothemy vs. Ectothermy -WAS[Re: [Re: [Re: DOWNY STEGOSAURS (WAS: Re: Feathers on Bloody Everything)]]]



Concerning endothermic versus ectothermic:

    Some people think that extensive parental care indicates endothermy.
This is logical, but not necessarily true - e.g. crocodillians.  It is
comforting to think that because some dinosaurs took good care of their
offspring, that they were like us, i.e. WARM!  I happen to think that many
of the arguments for endothermic dinosaurs are good, and that many dinosaurs
were somewhat 'warm-blooded'.  However, I don't think that ALL that evidence
is black and white.  Nor do I think that ALL dinosaurs were 'warm-blooded' -
and I certainly don't think that those that might have been, were
'warm-blooded' in the way most of us think of it (i.e. like mammals and
birds).

    One of the messages on the previous posts was about dinosaurs lazing in
the shade.  Another concerned how much activity an ectotherm could support.
The fact is that ectotherms can be very active, and do quite a bit.  The
major difference is that endotherms can sustain high rates of activity for
extended periods of time, and can do so in an wider range of temperatures
than ectotherms.

    I personally _feel_ that the various sizes of dinosaurs, and ecological
niches they filled, and the structural strategies employed throughout
dinosauria would indicate that several thermo-regulatory schemes would be
used.  For example, perhaps the earlier forms were closer to our (general)
view of current reptiles, but based on recent integument findings, it
certainly seems to me that several later forms were feathered.  This would
indicate the trend in some of the dinosauria towards 'warm-bloodedness' -
perhaps towards bird-like levels.

    As to use of feathers, I think that multiple uses and raison d'etres are
likely.  [For those of you who don't remember/know French - "reason for
being"].  I like the idea that feathers started as a unique way of ridding
the dinosaurian body of nitrogen by-products.  We know that feathers provide
insulation.  And we know that current birds use feathers for display
purposes as well as for insulation and for flying.  It makes sense that
feathers may have been used for display on dinosaurs.  It also makes sense
that some of the feathers may have been enlarged for improved display
purposes - prior to their ability to be used for flying.  (I also like Tom
Hopp's idea about the use of feathers for brooding).

    Feathers provide insulation, protection (see Japanese feathered armor
from 600-700 years ago), and display functions. And in flying birds, they
provide a majority of the wing area for lift (and control) to enable flight.

    The fact that we are now finding integument that shows feathers on some
dinosaurs shows how closely related dinos and birds are.  Since today's
birds are endothermic, we expect that their feathered dinosaurian relatives
were also endothermic.  This is logical but not necessarily true.  There are
recent studies showing that _Archaeopteryx_ may have been endothermic - and
would _still_ have been able to fly.

    All (macrosized, multicellular) animals have the need for some sort of
insulation, whether it's hair, feathers, fat, thicker skin, or thicker
shells.  Insulation works BOTH WAYS!!!  It keeps the heat out or in,
depending on the needs of the organism at a particular time.  Insulation may
be provided by elements in the environment (or as a shelter). [e.g. Hermit
crabs].



    By the way, concerning methods employed by modern lizards in cooling
themselves - I have heard of some lizards urinating on themselves to cool
their legs off.


    Oh well, more fuel for the fire....

            Allan Edels