Re: The new Archaeopteryx from... Wyoming?

[Tim Williams <twilliams_alpha@hotmail.com>]

Thomas R. Holtz, Jr. wrote:

> One thing of note, however: while the unit comprised of the ungual and 
> pedal phalanx II-2 seem to have been hyperextensible, the joint between 
> pedal phalanx II-1 (the proximalmost phalanx) and metatarsal II are not. 
> Indeed, it has a typical theropod shape for II-1, not the  highly 
> transformed one that is looking to be a good synapomorphy of 
> Deinonychosauria (now that _Rahonavis_ is over there...).

I wonder if this derived "highly transformed" shape is functionally 
correlated with the enlarged ungual?

Jeff Hecht wrote:

> Together with Pete Makovicky's analysis of Buiteraptor of a few weeks back, 
> this shows that early avian evolution was very complex -- more a very 
> tangled thicket of evolutionary sprouts than a classic tree with clearly 
> defined branches. {snip]

As you say, I think we need a larger sample of birds (avialans) before we 
can nail down the positions of _Rahonavis_, _Archaeopteryx_ and 
_Buireraptor_ relative to each other and to other paravians.

> Greg Paul was on the right track when he suggested that dromeosaurs were 
> flightless birds, but he now says it probably wasn't that simple. They may 
> have been evolving and losing flight far more easily than anyone had 
> thought.

To further muddy the waters, there is the issue of which particular aerial 
behaviors actually qualify as 'flight' (e.g., does 'phugoid gliding' 
count?).  Also, there is the difficulties (impossibilities?) associated with 
trying to reconstruct the flight performance of fossil theropods that have 
no extant analogs.

> Juveniles may have been stronger flyers than adults -- once their bones 
> solidified -- because their arms may have grown faster than their bodies.

Also, the overall dimensions of juveniles (such as the proportionally larger 
head) migh thave given them a more forward center of gravity/mass than 
adults - an advantage in both gliding and flying.  Juveniles might also have 
had an easier time climbing trees - another suggestion of Greg Paul's.

> We need a lot more analysis, particularly with birds added to the picture, 
> as well as more fossils. It should be fun for all.

Agreed!

Guy Leahy wrote:

> I had the opportunity a few weeks ago to view the mounted Buitreraptor 
> skeleton at the Field Museum.  I was struck by how gracile the skeleton 
> was.  It looked more like a long-armed troodontid in general form than most 
> dromaeosaurs... :-)

I wonder what putting _Jinfengopteryx_ into the matrix would do...?  It 
looks to be a long-armed troodontid originally mistaken for a true bird.  
Then again, what is a "bird"?!

Cheers

Tim