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Re: cause of Gigantism in sauropods

> Sorry, for not being clear: the
> hypothesized causal link would be that
> the dinosaur is able to consume the canopy of the tallest
> (and
> consequently largest) tree, if not, the forests formed by
> the said
> tree would reduce the primary production available for the
> herbivorous
> dinosaur needs.

Why would we assume that they would by necessity feed on the canopy? Assuming 
there's ample vegetation at the (say) 25 foot point of a 200 foot tree that a 
given sauropod could reach, that alone would create a browsing-height based 
selective pressure. In this case, plant height may have been driven by 
competition for sunlight against other trees, while still providing a selective 
force on sauropod neck size.