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Re: semilunate carpal



Graydon wrote:

Certainly; they *are* strong.  The question is why did they get that
way?

The usual answers come down to 'they were waving their arms a lot',
which I think covers the question of strength but not the question of
the particular restricted range of movement.

My answer is that the hands and forelimbs were used to grasp (or grapple or hold - but *not* manipulate) struggling prey. I think this might explain the limited mobility of the wrist/manus articulation and the extensive pectoral musculature dedicated to working the forelimb.



Well, really, imagine how much strength it takes to keep the kick with
the foot claw from bouncing the _Deinonychus_ *away* from the
_Tenontosaurus_, bucking or not;

Good point. Every action has an equal and opposite reaction.


those legs are the primary locomotor
organ of a grapple-and-slash predator, presumably one with a
considerable short sprint capability.

On the ground, yes.


The ancestral form that started developing the sickle-claw would have
had this same problem; how do you keep a clawed kick from making the
*second* kick much harder to deliver by bouncing you back from the prey
animal?

I would say the forelimbs and manus were used to hold the predator in place (such as when a _Deinonychus_ was holding onto a tenontosaur's back) as the slashing claw went to work to slash the prey.


(You know, I could be misinterpreting your response - it's been known to happen - so set me straight if I have the wrong idea).


I think that one is actually a bad example of typical behaviour; whoever
started that fight, it went really wrong for the _Velociraptor_.

I can't see how the entanglement was going *that* wrong for the _Velociraptor_. It had its slashing claws positioned under the exposed neck and belly of the _Protoceratops_. Maybe its hand had sustained some damage courtesy of the _Protoceratops_'s choppers, but I like the _Velociraptor_'s chances of walking away from the encounter alive more than the _Protoceratops_. (Of course, as we know, they both died, so we'll never know who "won".)


> >Is there a known biomechanical reason why the use of the 'predatory
> >stroke' might not have been to align the maniraptoran, relative to the
> >prey, rather than to move a small prey animal toward the jaws?

I'm thinking the prey was not small - at least for velociraptorines. As such, *both* hands were used to grasp the prey.




Tim


---------------------------------------------------------------------

Timothy J. Williams

USDA-ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163




-- graydon@dsl.ca To maintain the end is to uphold the means.


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