Re: New alvarezsaurid

[Dinogeorge <Dinogeorge@aol.com>]

In a message dated 98-03-24 02:33:12 EST, m_troutman@hotmail.com writes:

<< >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'.  >>

In this context, this is hardly illuminating. I don't think there's any way
you can show that a maniraptoran hand makes maniraptorans better predators
than the looser, relatively shorter, more mobile hand of earlier theropods.
Can you, for example, accumulate statistics on the kill ratios among
maniraptorans versus those among earlier theropods, and then relate these kill
ratios to the structure of the hand?

I think your predilection for the BADD paradigm has led you to the conclusion
that the maniraptoran manus must somehow have been better for predation (else
why would it have appeared in cursorial predators?), and that you are
searching for a way to demonstrate this presently undemonstratable
proposition.

In the BCF paradigm, the structure of the maniraptoran hand doesn't need this
kind of explanation; this kind of hand is retained in cursorial, nonflying
maniraptorans simply because it was present in their flying ancestors. And it
was present in the flying ancestors as a stage in the evolution of the modern
bird wing; we know this because the modern bird wing has a basically
maniraptoran design.

<<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. >>

Here again, we have no idea what phorusrhacids used their stunted wings for.
Have you ever seen a phorusrhacid hunt, or read an eyewitness account of what
it did with its wings? The arguments about how phorusrhacids hunted are
endless and circular, and lead to no confirmable conclusions. Their wing
anatomy may have the differences you describe, but there is no way you can
ascribe those changes to "hunting advantages" or anything else. To baldly
state that phorusrhacid wings were used to subdue prey is simply bad form,
since you have no way to show this to be the case.