Re: Claws on deinonychosaurs

[Phil Bigelow <bigelowp@juno.com>]

Ahh, good point!  I hadn't considered snagging as a frequent cause of
breakage.  I wonder how many deinonychosaur hook claws in the world's
museum collections show evidence of healing from a fracture, or evidence
of a chronic infection?

Titanosaurs had some some skin armor.  Perhaps this provides clues as to
the parts of the titans' bodies that were most frequently attacked by the
largest deinonychosaurs.  Could skin armor snag a curved claw and break
it?  Alternatively, were deinonychosaurs ever snagged by their claws and
then dragged to death by their prey?

Oh the <hypothetical> horror!

<pb>
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On Wed, 02 Nov 2005 11:27:34 -0800 (PST) don ohmes <d_ohmes@yahoo.com>
writes:
> 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
> > > 
> > > 
> > 
> > 
> > --
> > 
> > 
> 
> 
> 
> 


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