RE: New Archaeopteryx specimen with new foot details

[Tim Williams <twilliams_alpha@hotmail.com>]

Phil Bigelow wrote:

> >  In fact, as we get more basal specimens from each of
> > Pygostylia, Dromaeosauridae, Troodontidae, and Archaeopterygyidae,
> > they are getting far tougher to tell apart...
>
> Ironic that, with an increasing dataset, we may be headed toward a
> polytomy rather than away from one.

In other words, the anatomical differences among basal representatives of 
these groups are expressed as such a relatively small number of characters 
that it is difficult to resolve the precise sequence of divergence of these 
groups.

Jeff Hecht wrote:

> Flight has such clear advantages that there may have been multiple detailed 
> paths to flight within dino-birds who were already part-way there. Some may 
> have gone through a gliding stage, some may have evolved tree-climbing 
> capabilities so they could navigate the trees more effectively once they 
> got there.

I completely agree.  The thing is, if _Archaeopteryx_ retains the basal 
avialan bauplan, this plesiomorphic bauplan appears to have persisted into 
the Late Cretaceous in the form of taxa such as _Rahonavis_ - at a time when 
ornithothoracine evolution was in full throttle.  I like Jim Cunningham's 
idea that the long tail of these basal birds functioned much like an extra 
wing.  Microraptorans and perhaps scansoriopterygids represented other 
experiments in aerial locomotory behavior, which ultimately turned out to be 
evolutionary cul-de-sacs.

Furthermore, given just how energetically expensive flight is, it is not 
surprising that many Mesozoic avialan lineages gave it up: _Patagopteryx_, 
hesperornithiforms, _Gargantuavis_.  My gut tells me that deinonychosaurs 
(and maybe oviraptorosaurs and therizinosaurs too) are descended from 
maniraptorans that had limited aerial locomotory ability, but which were not 
true powered fliers.

Jeff Hecht wrote, in an earlier message:

> Today's Science reports a 10th Archaeopteryx, well preserved, showing new 
> characters on the feet and in the skull.

It's my understanding that of these 10 specimens, 2 or 3 are still in 
private hands...?  These include the "chicken wing", and maybe at least one 
more complete specimen..?

Cheers

Tim