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RE: Claw function in Deinonychus



Tim Williams (twilliams_alpha@hotmail.com) wrote:

<Hmmm.. are you sure?  I seem to recall that the sickle-claw of _Achillobator_
was proportionately quite small - compared to _Deinonychus_ anyway.>

  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).

  Measurement include:

  *Utahraptor* - body size, ~4-4.5m; pdII-3, 169mm (est. for missing tip)
  *Deinonychus* - body size, 3m; pdII-3, 75mm (est. for missing tip)
  *Velociraptor* - body size, 1.5-2m; pdII-3, 42mm
  *Sinorthosaurus* - body size, ~1m; mdII-3, 25.4mm (10% for pdII-3, ~30mm)

  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.)

<I know you're kidding, but somebody (a former member of this list) actually 
suggested this!  He proposed that the _Protoceratops_ was defending its
territory (or its eggs) against a roving _Velociraptor_.  In other words, the
ceratopsian was the aggressor.  (Hello Tracy if you're out there!)>

  Tracy, however, has a point, and up until one point, when Tracy published
this in his "How to draw Dinosaurs" series, there was a serious effort to
publish the aggressive omnivorous features of ceratopsians in _JVP_.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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