Re: Tiktaalik

[Tim Williams <twilliams_alpha@hotmail.com>]

David Marjanovic wrote:

> I don't think so. The toothplates and jaws of lungfish are quite 
> awe-inspiring. (For example lungfish don't have an upper jaw -- just a 
> palate.) The cocoon is almost unique among vertebrates as well.

I'm talking body plans.  So was Daeschler et al. (2006) in their _Nature_ 
paper.  The term "body plan" is even in the title.  No matter how 
awe-inspiring a lungfish's cakehole is, it's not going to help it move 
around on land.  Of course, no offense to lungfishes is intended...

> Sorry, I can't help it -- this all sounds so much like an argument for 
> ranks :^)

Oh no!  Not those horrible "ranks"!  I'm not talking typology here (heaven 
forfend!), but transformations involving locomotion in (or on) two different 
kinds of media.  Tetrapods (including ourselves) are still just uppity 
lobe-finned fish, and birds will always be theropods.  But both transitions 
involved major transformations, associated with water-to-land and 
land-to-air.  (The latter is still true even if birds evolved from arboreal 
theropods, because no known non-avian theropod is specialized for 
arboreality; they retain the terrestrial-bipedal body plan primitive for 
Theropoda.)

Not convinced?  Ask yourself this: Why did _Nature_ magazine dedicate a 
combined 18 pages to the discovery of _Tiktaalik_?  It made the cover too.  
It was not just because this critter was "photogenic" (though it was that 
too).

Cheers

Tim