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Re: Rahonavis; sickle-claws




Gerrit Hanenburg wrote:

But seriemas have curved claws on pedal digit III and IV too.

When it comes to the "sickle-claw", it's not just size but what you do with it that counts. The large size of _Deinonychus_'s second pedal ungual, combined with its ability to execute a wide arc of movement, suggest that it was wielded as a "slashing claw". As such, the enlarged sickle-claw was a specialized instrument designed for predation. (Although *maybe* the hyperextensible sickle-claw was initially evolved as a climbing device, or was co-opted for such a purpose later on... but that's another story.)


Anyway, this
can be quantified with methods such as used by Feduccia (1993)

Feduccia's quantitation study of bird claws has one major weakness: it did not determine whether the arc of curvature associated with perching ability was different to the dimensions for predation. This blows a big hole in the study - big enough for a tyrannosaur to walk through.


(Of course, there is absolutely no reason to assume that the use of claws for climbing/perching and for predation are mutually exclusive.)



Tim

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