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Re: tiny dinosaur



Certainly, the anatomical differences are great enough to limit any
comparison. I'm actually quite surprised that arboreal theropods
developed.

One could even argue that it represents a very different evolutionary
pathway, a kind-of alternative among arboreal paths to flight. I think
this is one of the things that is fascinating if one conceives of
evolution in terms of morphospaces first and then bauplans.

My reference to bauplans was within one group or the other - basically,
if there is a family of morphologically and ecologically similar
species, and they are experiencing similar pressures they are likely to
stumble down different routes. So a half-dozen flight evolution events
within the same family of species is quite likely.

Thanks for the more complete list of mammalian gliders - I wasn't aware
of a number of them.

-Jonas

P.S. You still left us out - just because we happen to reshape bits of
our environment into exoskeletons doesn't mean that it isn't an
adaptation, doesn't have evolutionary origins (or implications -
thinking disease transmission) and doesn't preclude us from being
mammals. We leave ourselves out of these lists all too often ;)



On Mon, 20 Jun 2011 10:30:48 +1000
Tim Williams <tijawi@gmail.com> wrote:

> 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.
> 
> 
> 
> 
> 
> Cheers
> 
> Tim