Re: Ceratopsian mass estimates

["Jaime A. Headden" <qilongia@yahoo.com>]

Greg Paul (GSP1954@aol.com) wrote:

<Tyrannosaurs were lean but powerfully muscled killing machines like all
running predators, there is no way they weighed much more than my mass
estimates, which are based on volumetric models rather than my life drawings.>

  Is there anyway we can arrive at the mass-estimating models made to come to
this conclusion? I know Greg's method is to build a model based on his
skeletons, and then use thew volumetric displacement method to estimate mass.
As with Andy's caution, however, this is still an estimate based on an
estimate. We are assuming a particular volume of air must be removed, and a
particular musuclar mass being placed in key regions, plus it is likely we can
arrange the ribs and the circumferential volume of the tail, neck, and trunk,
not to mention the limbs, in wholly different ways.

  Not that I think Greg is wrong, but even then, using his estimates versus the
work of Hutchinson by means of calculating leg musuclature in just
tyrannosaurs, the estimates may be off by a little. Not saying they are, but it
is a large margin of error that can increase mass by a tonne or so, or decrease
it. This isn't a little "dray vs. wet weight" debate, but it may be the
unquantified "how much mass can a muscle scar carry" debate. No one has noted
the degree of rugosity or height of relief (or even what "degree of rugosity"
is) much less determined how much muscle IS there based on comparative anatomy,
except for  Greg and Hutchinson ... yet both come to different conclusions.
Thus, I cannot trust either study until they use the same methods and arrive at
the same numbers OR use different methods and arrive at the same numbers.

  Anyways, summing up:

  I would like to see Greg's method and models illustrated in more detail,
since it seems to be a critical part of his work. A paper in biomechanics using
the mass-estimating models and how he came to his published figures would be a
decent work and wholly in line with his calculation work he's been doing
lately. Plus, I've always been curious. Compared to, say, 3D-spline modelling,
such methods may offer a digital versus physical model for mass reconstruction.

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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

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