Re: Dynamic modeling deinonychosaur claws

[Phil Bigelow <bigelowp@juno.com>]

Yes, but no one is challenging the cutting effectiveness of such claws. 
That is almost a given.  Deinonychosaur slashing claws are clearly
designed for piercing hide and for making a slashing cut.  But the
problem is that, sometimes, particularly in certain circumstances, very
efficient cutters can become rather fragile implements.

My interests lay in the real-world use of such a claw, not in how cleanly
it could cut.  If the prey item struggles during the attack (e.g., the
prey bucks, shakes, turns or lunges forward or backward), is the
deinonychosaur claw strong enough to survive such forces?

The answer is not self-evident.  If the foot claws were *only* used to
make a quick "slash and release" attack, then their strength may not
matter.  In that case, you are correct:  It is all about cutting.  The
strength of the claw become a minor issue.

But what if deinonychosaurs tended to hop onto their prey and "hang on"
(like today's big cats do).  If that was their modus operandi, then the
various torsional forces placed on the claw could be substantial.  What
is the magnitude of those forces, and what are the strength limitations
of the claw when each force vector is applied?

So, the big question is, are the "slash -n-release" vs the
"attack-n-hang" hypotheses testable?  I believe they are.

1) Inventory all of the deinonychosaur slashing claws in museum
collections and see if any healed damage is present. (healed fractures,
or persistent draining wounds in the bone, etc.).  Note the position of
the healed damage, tabulate the results, add some stats, and then move on
to step #2.

2) Inventory all of the deinonychosaur hindlimb bones (and while yer at
it, do the forelimb bones too) in museum collections and search for signs
of joint disease (arthritis, etc).  If these critters were being shaken
around like rag dolls as they hung from their panic-ridden prey, it is
likely that dislocated joints were common vocational-related maladies for
deinonychosaurs.  If a deinonychosaur's slashing claw became snagged
behind a piece of dermal armor in the prey, then the potential for
disaster is very real.  Repeated joint trauma will eventually lead to
loss of cartilage, and eventually to disease (erosion) of the bone,
itself, particularly in old age. Tabulate the results, add some stats,
and then go home and have a beer.

<pb>
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On Thu, 03 Nov 2005 05:29:09 -0700 paul w sparks <pws@psparks.us> writes:
> Well said. But I believe that any modelling that does not take into
> consideration the piercing and cutting of the skin as well as the
> effort to slice through muscle. Just take an old chicken from the
> market and compare what it takes to slice throught the skin and 
> muscle
> vice just cutting throught the muscle alone. Probably there are 
> other
> things to consider, I don't know.
> p sparks
> 
> > -------- Original Message --------
> > Subject: Re: Dynamic modeling deinonychosaur claws
> > From: "Jaime A. Headden" <qilongia@yahoo.com>
> > Date: Thu, November 03, 2005 12:22 am
> > To: dinosaur@usc.edu
> > Cc: bigelowp@juno.com
> > 
> > Phil Bigelow (bigelowp@juno.com) wrote:
> > 
> > <All well and good.  But note that my question was about the 
> relative
> > *strength* of a curved blade compared to a straight blade with the 
> same cutting
> > surface length.  In particular, the relative susceptibilities of 
> each to
> > torsional stresses and the relative shear strengths of each.>
> > 
> >   Historically, long curved blades such as scimitars and katana, 
> developed from
> > a need to increase the reach of a blade and thus the need to draw 
> the blade,
> > which is eased with length as you increase the curvature of the 
> blade. My
> >BIG SNIP
> 
> 
> 


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