Re: New alvarezsaurid

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

>      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?

    It sounds like you misunderstood. My point was that the maniraptoran 
hand is not suited for hunted and they did not hunt using it as a main 
"tool". 

Of course you cannot accumulate stats on the kill ratios, however nice 
it may be. I'm not saying that because ( in my view ) the maniraptoran 
hand was really unsuited for hunting that they weren't effective hunters 
( in the predaceous clades ). What I am saying is that the hand is 
really suited for other tasks.  

>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.

    You misunderstand. I'm saying that it did not evolve for hunting. 
And I think you are assuming that I believe in the " ground-up " origin 
of flight; I believe in the trees-down origin of flight. 

>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.

   Of course. Though I would not say flying ancestors, it may have 
evolved for climbing like Chatterjee proposes.  

><<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.
>

    Let's look at something. You yourself state that the maniraptoran 
manus and carpus is a step toward the modern bird carpometacarpus. Now 
then, if that is true we should look for an analog for the what would 
happen if a flying hand is coopted for hunting like in phorusrhacids. 
Since the maniraptoran manus is that of a flying form and does not 
confrom to the predaceous phorusrhacid manus, then we can assume that 
the maniraptorans did not have a manus that is suitable for hunting as 
Padian and Gautheir suppose. This shows that the frequently sited 
"predatory stroke" of the maniraptorans is not for predation. These 
posts were actually an argument against the "ground-up" hypothesis. You 
have misunderstood what I have been saying about phorusrhacids, I did 
not describe any specific hunting modes or styles, I just stated that 
the phorusrhacids had forelimbs adapted for predation. Since 
maniraptorans ( the predaceous ones ) did not have the same sort of 
forelimb that phorusrhacids had, it can be said that the maniraptoran 
forelimb was not evolved for predation and was a minor or nonexistent 
factor in predation. I am making an informed judgement on the function 
of maniraptoran forelimbs using a frequently sited analog. The judgement 
on maniraptoran forelimbs is that they had no predatory advantage and 
did not evolve for predation. I am not saying that they were inferior 
predators or anything else like that. I am not conjecturing on the 
phorusrhacid style of hunting. I am not a supporter of the "ground-up" 
hypothesis. I am a supporter of BAMM and believe Chatterjee's notion of 
the evolution of the maniraptoran manus. I hope there will be no more 
misunderstandings.

Regards,

MattTroutman

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