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Re: tiny dinosaur

Jonas Weselake-George <ee555@ncf.ca> wrote:

> Of course, the interesting question here is: If two species in the same
> genus independently evolve in a direction - are we talking about
> separate occurrences? Similarly, we could ask if related species, in
> similar niches, with similar bauplans evolve in the same direction - is
> gliding evolving separately or once using the same evolutionary pathway?

It's interesting that you mention 'bauplans', because the one thing
that unites all gliding mammals is their specialized arboreal
abilities.  These animals live in the canopy, and so use aerial
locomotion (gliding) as a way of commuting between trees.  It's a far
more energetically efficient way of getting around than climbing up
and down tall trees - and much safer too.  I'm willing to bet that
this is how bats (Chiroptera) came to acquire powered flight.

However, theropods do not fit this 'bauplan'.  Their climbing
abilities were weak, and even the maniraptoran relatives of birds
retained the bauplan of a terrestrial biped, not an arboreal
quadruped.  Although maniraptorans like microraptorines, _Pedopenna_
and _Archaeopteryx_ show clear adaptations for aerial locomotion, this
was not tied to a specialized arboreal lifestyle that favored
commuting from tree to tree.  So for this reason, comparing gliding
(and flying) theropods) to gliding mammals has its limitations.