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Re: pterosaurs, bats, flying theropods




On Fri, 20 Dec 2002, Jaime A. Headden wrote:

> Other arguments seems to focus on
> bats becoming nocturnal, to avoid diurnal birds, but this is similarly
> bunk as it is first a generality (only most microbats are nocturnal), and
> second there are plenty of diurnal bats (all megabats) and nocturnal birds
> (owls, swiftlets, etc.) which live in the same areas as microbats.

One may argue with and ridicule pet hypotheses based upon extrapolating
extant behavior back to the Cretaceous.  However, one should not
argue that an extant, fully observable phenomenon, is not generally
true by arguing it's only a generality!  Niches are available to all body
plans.  If one body plan (birds) dominates the diurnal niche to the
extent birds do, we must admit this is not just a matter of chance: birds
have it over microbats in the day time.  And it's silly to say that bats
just _give_ the day time to birds--they would expand into this niche if
they could.  Then we look at reasons why birds have it over bats.  As you
mention, they both share a wide range of food resources; and it's hard to
imagine that one species could simply _out-eat_ a competitor.  A prime
hypothesis for investigation should be that bats are more likely to be
prey in the day time than birds are.  To explain a general phenomenon, we
need a general selective agent.  Predation is such an agent.  Predation
may also explain the relative immunity of megabats and therefore their
ability to forage at midday.

After all, feathered wings are likely not identical in effectiveness as
non-feathered wings.  Which are better?  And while bats and pterosaurs are
disimilar in many ways, they are similar in this crucial aspect: they
don't have feathers.  Are feathers a big deal in flight?  If they are,
they probably played an important role in the Cretaceous sweepstakes, just
as they do today.