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Re: Large last gasp of pterosaurs



On Thu, Jan 22, 2004 at 11:40:39AM -0600, Tim Williams scripsit:
> John Bois wrote:
> >Except that this then opens up the far more interesting question of
> >what complex ecological factors actually killed most pterosaurs.
> 
> Competition with birds?

There are, to my mind, four serious problems with invoking 'competition
with birds'.

1) we don't have any evidence for it, no strata where the pterosaurs
give way to shore birds, frex.  The few mixed communities we have
evidence for have way more pterosaurs than birds.  (7 Archeopteryx
versus how many pterosaurs?)

2) pterosaurs had a very considerable head start for feeding
specializations and a fundamentally different mode of flying; it's not
clear that there would be direct competition for food, or that early
birds could reasonably expect to compete with pterosaurs for food at
all.  Food that different modes of flying made available to birds that
wasn't available to pterosaurs wouldn't have been part of the
pterosaurian diet in the first place.

3) both groups of fossils are generally very rare, sparsely represented,
however you want to put it.  I don't know of any case where someone has
been able to demonstrate that there is a statistically significant
decline in the pterosaurian population.

4) nest predation scenarios seem to assume altricial-model mostly
helpless nestlings.  I don't think this is a supported assumption -- do
we have any pterosaur nestling fossils? --  and a baby Pteranodon or a
baby Quetz. half the size of its parents would be quite well able to eat
an eagle if the eagle was crazy enough to try to predate it.


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