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Re: Claw function in Deinonychus



I've never been convinced that 'disembowelling' was a plausible
function for such a strongly curved claw on a very flexible digit.  The
ostrich and cassowary are widely reputed to be able to disembowel
humans, dogs, lions etc. with a front kick, and though I do not have
details of any documented cases this seems worth investigating (just
annoy your local ratite with a pig carcass on a stick?). Ratite claws
are not especially sharp-tipped, thick and strong but relatively weakly
curved...

I am pretty certain (those by no means absolutely so) that the disemboweling blows delivered by ratites are really abdomenal ruptures caused by the extreme force of the blow, rather than a slicing attack. If anyone can confirm/deny this based on some published observations, that would be great. I don't have any on hand right this moment.


As Manning et al conclude, a strongly curved claw with an
elliptical cross-section is not an effective cutting tool...

Technically, cats have a claw with an elliptical cross-section, and they can both grab and lacerate. There is a bit of an edge, granted, but it is not preserved clearly in the unguals. Raptorial birds mostly puncture and hold, but they too can cut (trust me, I've been on the receiving end), and they also have elliptical cross-sections. My personal hunch (and it's only a hunch thus far) is that strongly curved claws with an elliptical cross-section can be a good cutting tool under certain circumstances (but are better hooking organs under other circumstances).


If the claw morphology evolved in association with arboreal
foraging (for insects or small vertebrates), nocturnal perching, or
juvenile escape behaviour in small generalists, its use in predation
would be an 'exaptation' that might have been critical in allowing
specialisation on large prey (which may or may not have actually
occurred).

That is one idea I too had in mind.

There are two related thoughts I'd like to throw into the mix real fast:

1) Do not forget about the function of the forelimbs in predation. They manual claws are nearly as large and dangerous in many dromeosaurids as the enlarged pedal claw.

2) Big-game hypercarnivores of the modern world rarely tackle animals hundreds (or even tens) of times their size. Dromeosaurids could have been hunting animals say, 60 or 70% of their size, and that would still very much be hypercarnivory of an impressive level (and explain the level of weaponry possessed). Assuming such (much more reasonable) prey sizes, the pedal claws are more reasonably interpreted as combination grabbing/slashing weapons.

Cheers,

--Mike Habib