Re: Claws on deinonychosaurs

[don ohmes <d_ohmes@yahoo.com>]

Well, more, I think. When a straight cutting edge runs
into resistance (bone, gristle, hide folds), it tends
to angle back and slide off as forward motion
continues... the forwardly curved edge functions as a
hook, which could snatch that sucker right off your
toe. Or break it. 

Don

--- Phil Bigelow <bigelowp@juno.com> wrote:

> 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>
> --
> 
> 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
> > 
> > 
> 
> 
> --
> 
>