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Re: Ceratopsian mass estimates



Phil Bigelow (bigelowp@juno.com) wrote:
 
<Doing a "point count" of a thin section of a small piece of the fossil bone
should give a pretty good percentage of any added minerals.  Since Weight(of
the added mineral) = Density(of the mineral) X Volume(of the bone), the total
weight of added minerals can be calculated.

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.>

  Plus...

  Taphonomic diagenesis can destroy original bone structure, and bone structure
can vary throughout an element, as in the proportion of medullary to cancellous
to cortical bone. This means that the only reliable means of determining how
much original bone material would be present to estimate weight on would likely
be through CT sections, each measured per zone and each zone measured
independantly, then volume arrived from that. Epiphyses of bones will have a
different relative mass than the diaphysis, and the weight of the medullary
chamber will require knowing the weight of the medullary material. How much
does the skin weigh? Or blood-vessels? We don't need to know this with extant
animals since weights can be drawn directly and mass from that, but diagenic
"bone" is no longer bone, and even the volume of that can be different from the
original material.

  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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