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Re: Claw function in Deinonychus





And the sickles of *Utahraptor* (inferred) are for an animal twice the length
(?) and maybe twice the mass or so, is apparently only 50% larger, smaller
proportionately than in *Deinonychus*. I don't have the papers at hand to check
on this, so am working from memory. The claws of *Velociraptor* are about 85%
or a little larger than those of *Deinonychus* and the animal is around than
50% the mass and 65% the length of *Deinonychus*. The claws of
*Sinornithosaurus* are also very large for it's body, but for a 1m animal, the
relative claw length seems closest to that of *Deinonychus*, estimating for a
10% increase from the second manual ungual (since the pedal ungual of the type
of *Sinornithosaurus* is missing the thagomatic claw part, but preserves the
base of the ungual).

The info above makes it appear as if my hunch was wrong (nothing shocking there); I am a bit confused, however, because your ratios seem to say the opposite...


 So, the proportions are:

  *U.* - 4500 / 169  = 0.0376
  *D.* - 3000 / 75   = 0.025
  *V.* - 2000 / 42   = 0.021
  *S.* - 1000 / 25.4 = 0.0254

We have an allometric increase in claw size with decreasing body size,
possibly suggesting a difference in function given size as well as a possibly
reduced function for weight-bearing with a size increase. (All claws were
measured from the center of the articular face to the tip of the ungual, btw.)



That looks more like an allometric increase in claw size with increasing in body length; the ratio for Utahraptor (0.0376) is greater than the other three, smaller species (all less than 0.03). Utharaptor is 1.5x longer than Deinonychus, but the claw length you list (169mm) is 2.25x the claw length in Deinonychus.


Actually, from the small sample above (which is obviously too small for any real tests, but is still informative, thanks so much) it appears that the oddball is Sinornithosaurus...it "should" have a claw length less than 0.02x its body length, but it instead has claws of Deinonychus proportion.

Thanks for taking the time to gather that prelim data!

--Mike Habib