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Re: Sauropods and Endothermy



Stephan Pickering wrote:
> Thermoregulation is far
> more complex than some have thought: marine iguanas
> are capable of foraging, e.g., in icy cold waters, yet
> do not collapse dead.

Juveniles have to limit their time in the water to avoid just this. They
are restricted to food sources closer to shore. Only after reaching a
certain size can they feed on the richer, and deeper, food sources
enjoyed by adult iguanas. Even then, adults can only stay out for a
certain amount of time. Hence their black colouration, which allows them
to warm up again quickly by basking.

I suspect whales suffer from a similar problem (despite them being
endothermic). They have to move to warmer waters to calf, and only once
the offspring is a certain size can they take it to colder waters. 

I'd imagine that sauropod offspring would suffer the same problem, no
matter what their metabolic situation. The sauropod track ways along the
coast of Western Australia may show them migrating to warmer climes to
breed (since at the time this was the only route to the northern parts
of Australia). Or, of course, they may not. :)

Does anyone know whether sauropod remains have ever been found above
about 75º of palaeo-latitude? That's approximately where Lightning Ridge
was during the Early Cretaceous. If not, then perhaps a lot of sauropods
were restricted to areas that were within about six months (or less) of
migration from suitable nesting areas.  New Zealand's sauropod remains,
at least that I'm aware of, are restricted to a single rib fragment that
is not diagnostic enough to determine its relationships (assuming it IS
sauropod).

Of course not all sauropods may have been restricted by their
reproductive behaviour. Modern ectothermic reptiles, although largely
confined to warmer climates, still have some species that can tolerate
colder climates. Tiger snakes in Tasmania are larger and darker in
colouration than many of their mainland cousins. Red-bellied black
snakes, as well as being totally black on top, also give birth to live
young. As HP Pickering said; thermoregulation adaptations (especially
amongst ectotherms, but not exclusively) can be surprisingly varied and
complex.

-- 
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Dann Pigdon                   Australian Dinosaurs:
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://www.alphalink.com.au/~dannj/
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