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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 of
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 (cited
in 1989, but it's the same equation from his earlier paper). For the bipeds
(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 there.
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.