Re: Claws on deinonychosaurs

[Phil Bigelow <bigelowp@juno.com>]

No one has mentioned the relative shear strengths of long straight
unguals vs long curved unguals.  With a curved claw, the cutting surface
length can be quite long, yet the entire claw is shorter overall.

All other things being equal, could curved cutting surfaces be less prone
to breakage than straight cutting surfaces with the same blade length?

<pb>
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On Wed, 02 Nov 2005 13:15:36 -0500 Michael Habib <mhabib5@jhmi.edu>
writes:
> Since claw shape seems to be featuring in some of these posts, I 
> would 
> like to mention that a straight claw would, in fact, be better for 
> slashing than a curved claw.
> 
> This means the claws of deinonychosaurs remained curved through the 
> 
> evolution of the lineage for one of two reasons:
> 
> 1) Phylogenetic/developmental constraint (claws are ancestrally 
> curved, 
> curve is maintained).
> 
> 2) There was at least some importance to piercing/hooking; either in 
> 
> addition to, or to the exclusion of, slashing cuts.
> 
> With regards to piercing, from a pure physics standpoint: Using a 
> curved weapon that is swung has the advantage of focusing a lever 
> movement (the strongest movement of most animal limbs) into a 
> piercing 
> action. Piercing with a tip is much more effective at deforming a 
> stiff 
> or semi-stiff surface (say, thick skin, scales, etc) than slashing 
> with 
> an edge.
> 
> Of course, part of the difficulty with looking at fossil claws this 
> way 
> is that curvature is somewhat uncertain (owing to a lack of the 
> keratin 
> sheath in most fossils).  Then there is the whole issue of how 
> straight 
> is 'straight' and how curved is 'curved'.
> 
> --Mike
> 
> 


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