Re: New alvarezsaurid

["Matthew Troutman" <m_troutman@hotmail.com>]

><<  Regardless, a mobile 
> manus is not a predatory design. A manus where the phalanges are 
> parallel to the radioulna is better for "prey handling" because it 
> resists strain and is inheritantly more stable.  >>
>
>I don't think that this has ever been demonstrated or even can be
>demonstrated; I don't even know what "better" means in this context.

     I mean mobile in the way the semilunate makes it mobile. "Better" 
in this context means 'more suitable'. 

>If all
>you have is a mobile manus as a predator--inherited from ancestral 
forms that
>had a mobile manus for grasping and climbing in trees, for 
example--then that
>is what you have, and you make the best of it. If you believe that a 
manus
>such as you describe is "better" than a mobile manus, you should show 
why you
>believe this.

    In phorusrhacids, the ancestral manus was of a flying form, and it 
did not stay that way. I ask _why_ did phorusrhacids lose the ability 
for the manus to "swivel"? Attention must be put on the function of the 
forelimb and manus of phorusrhacids. They both were used for subduing 
prey; using this exapmle you can see that a manus with limited rotation 
can be used for prey seizing. Most birds have a rounded carpal block, 
which allows them to tuck their wing. Phorusrhacids have a squared 
carpal block, which means that the manus lies parallel to the radioulna. 
Using the phorusrhacids as an example, it can be shown that a stiffened 
manus in the sense of rotation, is very advantageous for bipedal 
predators that are similiar to theropods. 

I am not saying that maniraptorans were not predators, just that the 
manus is incongruent with the notion that it can be used for grasping 
and prey handling.

 In BCF, the manus becomes elongate and stiff because this is a
>clear aerodynamic advantage--an improvement to the wing that is shared 
by all
>maniraptorans (not all of which are predators), flying and nonflying 
(by
>descent)--not a predatory advantage. And in flying maniraptorans in any 
case,
>the phalanges are practically at right angles to the radius and ulna, 
not
>parallel to them as you describe.
>

    The manus may have also elongated for climbing. And I did not 
describe the phalanges in maniraptorans as being parallel to the 
radioulna, I just described phorusrhacids in that sense.

MattTroutman

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com