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endo vs. ecto



And yet again I feel compelled to point out that the theropod
formerly known as sinosauropteryx has the carbonized remains of insulatory
structures along the neck, back, and patches of the tail. while said
carbonized remains are indeed absent from the rest of the body, their
impressions remain below the neck, as far as I can tell. We are informed
from Japan that a larger specimen has said insulation from all over the
body.
        Feduccia mentions how it is that crocs survive as far north as
they do when he debates the subject in his book.
        they survive by remaining in water and breathing through the ice.
Turtles, I believe, can descend into the mud and stay there, and
presumably, their low metabolisms at such temperatures combined with the
higher concentrations of oxygen allowed by colder water mean they can
survive by absorbing oxygen directly from the water through the
anus.survive by absorbing oxygen directly from the water through the anus.
(this is as I understand things, not Feduccia). I presume snakes survive
by migrating underground to places where it does not become cold enough to
freeze. some animals (mammals, even) can produce an antifreeze that
prevents them from freezing to death at temperatures around zero. A very
few (a kind of frog) can actually survive being frozen. But not many.
Recall that the croc thing works only if the water doesn't freeze entirely
(and so freeze the croc with it). If I recall, labyrinthodonts are known
from the Australian dino site; they may have employed a turtle-like
strategy.

Paleoclimatology is limited, but it sounds as if the temperature very
likely dropped below freezing for long periods of time, long enough to
freeze a dinosaur or at least extremities thereof. So how did they prevent
this? Migrate? This would be at odds to the dinosaurs proposed which were
highly active for brief periods of time but spent most of the day lazing
around. How would T. rex and ceratopians get out of the polar regions fast
enough to avoid getting freezerburn? 
        Modern mammals and birds, of course, have their own strategies,
which involve generating their own heat.

        Feduccia does note that Horner's duckbills imply growth rates only
about 2/3 of modern mammals. I'm open to the idea that dinosaurs(some or
all) had a lower metabolism, and so, slower growth rates- marsupial,
monotreme, or kiwi level endothermy, for example. This seems to support
such a view, and importantly, it fits in reasonably well with all the
lines of evidence cited by endotherm proponents.
        Those arguing for ectothermy, however, don't even attempt to
produce a model of dinosaurian physiology consistent with the many data
which are used to argue for endothermy. They merely write them off as
irrelevant. This doesn't mean we should automatically write off their
results, but who can blame many of us for being skeptical and reluctant to
embrace these claims because of this? 

        Nick Longrich