Re: semilunate carpal

["" <ptnorton@msn.com>]

Tim Williams wrote:

> The hands (both at the same time) were used simply to sieze the prey and 
> hold on to it while the jaws and/or feet dealt the killer blow.<

But holding onto struggling prey requires a powerful grip, which the 
sideways folding wrist significantly limits.  That noncoplanar arrangement 
of joints and muscles simply doesn't make sense as an innovation related to 
grasping or holding anything.  It does, however, move the hand and extended 
fingers into a coplanar arrangement with the forearms when the arm is held 
outward from the body and horizontal to the ground.

> the jaws and feet (especially in dromies) did most of the work.<

They had to, since the hands were becoming much less useful in that regard.

> In other words, in maniraptoriforms, the hands and arms became instruments 
> dedicated to prey capture, not feeding.<

The hypertrophy of the arms and hands could also be explained as selection 
for increased lever arm length and turning moments.

PTN


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