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Re: Ceratopsian mass estimates

Dear Andrew and List,

    I think that your weight estimates for ceratopsians is more on the nose
than other's previous interpretations. This is based on my own extensive
study of these dinosaurs through sculpture. I know that saying " Occhams
Razor " on this list makes a considerable amount of members start howling at
the moon and frothing uncontrollably, but here it is anyways.
    Modern large to giant land mammals, that have generally the same mass as
big ceratopsians, weigh in at about what Andy's estimates dictate.A White
Rhinoceros maxes out at about four tons. It is roughly the size of a large
ceratopsian such as Pachyrhinosaurus. A really large African Bull Elephant
can exceed ten tons in weight. Humongeous ceratopsians such as Torosaurus,
Pentaceratops and Triceratops are all in and around the same mass as each
other, and yon pachyderm.

Cliff's Razor
   ----- Original Message ----- 
From: "Andrew A. Farke" <andyfarke@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, April 20, 2005 1:10 PM
Subject: Ceratopsian mass estimates

> Greetings, DML. . .
> I just finished some mass estimates for ceratopsian dinosaurs (part of
> background work tangential to my dissertation), which I thought might be
> interest to the list. First, an explanation of my methodology. . .
> I captured humeral and femoral shaft diameters from the supplementary info
> file for Chinnery 2004. Because Brenda did not give circumferences, I
> assumed that I could use the shaft length and width measurements to
> approximate circumference. Then, I plugged these values into Alexander's
> equation for estimating body mass from femoral+humeral circumference
> in 1989, but it's the same equation from his earlier paper). For the
> (i.e., Psittacosaurus), I used the modified equation (also cited in
> Alexander).
> The results are as follows (masses in kg and pounds):
> [Taxon, Specimen, Mass in kg, Mass in lbs.]
> Psittacosaurus, AMNH 6538, 6 kg, 13 lbs.
> Psittacosaurus, AMNH 6541, 16 kg, 36 lbs.
> Protoceratops, CM 9185, 44 kg, 97 lbs.
> Protoceratops, PIN 3143/5, 82 kg, 181 lbs.
> Avaceratops, PNAS 15800, 369 kg, 814 lbs.
> Chasmosaurus, NMC 2245, 1984 kg, 4374 lbs.
> Chasmosaurus, AMNH 5422, 2593 kg, 5716 lbs.
> Styracosaurus, NMC 341, 3723 kg, 8207 lbs.
> Triceratops, Kelsey, 5231 kg, 11533 lbs.
> Triceratops, USNM 4842, 11112 kg, 24496 lbs.
> The Triceratops estimates are scarily high--11 tonnes for the USNM
> specimen?! I plugged in the measurements from Hatcher et al. 1907 (which
> gives actual circumferences), and got pretty similar results:
> Triceratops, USNM 4842, 10208 kg, 22505 lbs.
> For the most part, the estimates are higher than others floating out
> For instance, Greg Paul published an estimate of around 1.5 tonnes for
> Chasmosaurus (vs. 1.98 tonnes for my estimate--admittedly not based on the
> exact same specimen, but they should be in the ballpark at least!). Greg
> estimated 6.4 tonnes for the Triceratops USNM 4842 (vs. 11 tonnes for
> mine!).
> I should state that I trust my estimates about as far as I can throw them.
> But, I just wanted to put them out there to see what people think!
> Best wishes,
> Andy
> References:
> Alexander, R. M. 1989. Dynamics of Dinosaurs and Other Extinct Giants. 167
> pp. Columbia University Press, New York.
> Chinnery, B. 2004. Morphometric analysis of evolutionary trends in the
> ceratopsian postcranial skeleton. Journal of Vertebrate Paleontology
> 24:591-609.