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Re: Query: Evolution of Pterosaurs



>Escape from predators seems to be the primary cause (for me, at any rate).
>Because when you take away the predators (say in an island environment),
>volant birds often evolve into larger, ground-dwelling, cursorial forms.
>Then, once the animals start making use of the trees, lots of other
>opportunities open up.
>

This does happen in island situations, but other forces may also have been
involved in such cases (eg arboreal birds may disperse more easily, and find
as a result open niches on the ground in island ecosystems).  OTOH, there
probably was a pretty good-sized arboreal insect fauna waiting to be eaten
back in the Triassic.

In short - if archosaurs went into trees back then there were reasons to do
so besides predator avoidance, though that could well have been one of the
factors.
--
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
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