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RE: How much does a dino weigh?

> From: philidor11 [mailto:philidor11@snet.net]
> Thanks for your edifying post on theropod size.
> As long as we're dealing with size issues, mind if I ask:  can a dino's
> weight be estimated with substantial confidence?
> I've seen published numbers, and wondered how everything from
> amount of fat
> to internal organs to muscle tissue (how thick and how heavy) to bone mass
> has been decided.
> What margin of error should I keep in mind?
> Thanks all over again.

Okay, things to keep in mind:

Mass is a property of individuals, not taxa.  One individual _Allosaurus_
might mass 1.2 tonnes, another 2 tonnes.  The best estimates are those tied
to specific individual relatively complete specimens.  This is particularly
marked among creatures like dinosaurs that go through MAJOR size changes:
remember that even the biggest titanosaurs are born as individuals smaller
than any one reading this list!

Furthermore, as any of us can testify, an individual's mass can vary over
time even without regarding ontogeny: some days/weeks/seasons we've put on
extra weight, other times we lose it.  The amount of variation in mass in
dinosaurs in regions with more extreme seasonality might be expected to be
greater than those in more equitable climes.

So, errors of 25% might not be unexpected for mass calculations on good
specimens, and much greater for incomplete forms.  Of course, the real test
for this would be taking a number of skeletons of different modern taxa from
individuals whose life mass was known, then estimating the mass from the
skeleton, then comparing these estimates to the known mass.  As you might
imagine, this would be a sizable and time-consuming effort.  Nevertheless,
it would give some statistical idea as to the expected accuracy of mass
calcuations based on fossil bones.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796