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Re: tyranno growth

On Tuesday, August 17, 2004, at 12:36  AM, GSP1954@aol.com wrote:

Took a look at the tyranno growth paper. The authors note that the body mass
estimates based on femoral circumferance are conservative. Indeed. The value
for Tyrannosaurus is just a little low, but those for the others are low by a
factor of two or more. Gorgosaurs, albertosaurs and daspletosaurs were very
large tyrannosaurs whose volume shows they massed about 2.5 tonnes. No way they
were only one fifth the size of Tyrannosaurus, at the mass of wee cattle. An
example of the perils of using limb bone circumferance as indicators of mass,
the relationship between the two being highly inconsistent.

One thing that's been bothering me about this study since it was released is the growth ring theory. Can anybody here explain exactly what causes growth rings? To my understanding, the prehistoric[or at least, before the most recent ice age] climate was pretty much warm all year round. The trees that we co-exist with are subject to changing seasons including winter, when as far as I know growth stops/halts, only to resume in spring. Is it this stop/go growth that causes the 'growth rings'? If so, then one could see how counting rings from a creature that lived in a presumed fairly constant ecologic environment could be prone to error.
I'll just sit back and wait now for someone to disprove what I've just said - I love the scientific pursuit of truth.