Re: functional morphology of killing claws and teeth

[Jeffrey Martz <martz@holly.ColoState.EDU>]

> The idea that dromaeosaur claws were used for slashing has always bothered
> me.  It always seemed to me that a better slashing design would be a fairly
> straight, bladed claw like that of the cassowary (which certainly does use
> it for slashing).  

     Exactly; I am talking about the slicing mechanics of the claw itself.
A long, straight, blade works better for slicing then an inwardly curved
edge like dromeosaur claws, because it can actually be drawn across the
surface it is cutting.  It doesn't seem like you could do that with a
dromeosaur claw, unless you are trying to put a groove around a
broomstick.  Dromeosaurs would have to press down with the edge of the
claw _without_ slicing once they had dug in; the inward curvature of the
claw just doesn't allow it to be drawn very far, if at all.  The amount of
force a dromeosaur would have to use to cut this way without slicing would
have to be pretty impressive.  
     A convexly curved blade works better then a straight blade works
better then a concave blade.  It seems that the curvature of the
dromeosaur claw couldn't be much worse for a slicing instrument.  
     The hyperextendable toe bringing the claw down would be acting to
penetrate, not slice.  Also, I would imagine that flattening the blade and
sharpening the edge a little would make actual penetration easier, even if
it didn't facilitate slicing.  Someone who knows what they are talking
about can elaborate on or correct that.              
     A forthcoming paper will be discussing other problems and
alternatives of the "slicing" dromeosaur claw model.  Sorry, I'm under
orders...           

LN Jeff
O-