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Re: comment-therizinosaurs

2011/10/9 Jaime Headden <qi_leong@hotmail.com>:
> What sense does it make that an animal with elongated, tranversely thin 
> unguals would use them only for defensive purposes?
> There was the idea that they were useful for digging (not usueful at all, 
> being thin) or for "hooking" vegetation (which would ask for strong 
> curvature), but even so, it makes odd sense to evolve great size, apparent 
> herbivore traits, and then large thin unguals not just on the hands but the 
> feet also.
> I wonder, but cannot test at the moment, that the unguals were sheathed in 
> keratin that did not just copy the shape of the underlying bone, and as such 
> _could_ be broader or bear features that make them good at digging or 
> destroying earthen structures or for tearing into various objects in general. 
> That they are present on the feet, which seemingly would never reasonably be 
> involved in defensive posturing, implies that the they (and by this I mean 
> the claws in general) were not merely for display and defense.
Interesting ideas...
Although I would hesitate in that relatively straight unguals are not
well suited for dealing with branches: the African elephant have
relatively straight tusks which seem to deal well with branches (not
at hooking them, granted, but helpful in breaking them). Accepting a
use in fighting, I do not see much problem in a therizinosaur kicking
with hindlimbs as well as using forelimbs in defense or offense. Is
there the possibility of compressed claws being useful to cut some
relatively though plant material as cycads?