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Re: Ceratopsian mass estimates



> Date: Thu, 21 Apr 2005 15:17:37 +0000 (pd)
> From: Phil Bigelow <bigelowp@juno.com>
> 
> Upon further reflection, however, I don't think there is an easy way
> to calculate the original weight of a fossil bone.  There are too
> many variables to consider: 1) Permineralization 2) Retention/Loss
> of bone collagen 3) Density change via recrystallization of the bone
> apatite 4) Degree of bone vascularization.  Etc. etc. etc.

Yes.  I think a more reliable approach would be to measure the
_volume_ of the bone and multiply it by the average density of bones
from the same region of a similar animal (e.g. sauropod femur assumed
to have the same density as elephant femur).  This approach first
occurred to me when I read Russel et al.'s (1980) estimate of the mass
of _Brachiosaurus brancai_ as a piddling 15 tonnes.

That approach would probably work OK on limb bones (assuming you could
find a way to measure their volume that didn't involve lugging them
into giant baths).  It wouldn't get you far with the vertebrae, as the
extensive pneumatisation is invariably filled with matrix that would
in many cases double the apparent volume of the bone.  You could
correct for this using known air-space proportion (ASP) figures for
the taxon you're working with, but this is another layer of
uncertainty.  (Also published ASP figures are still very thin on the
ground).

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