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Re: Ceratopsian mass estimates



A shown by the original data sample in the Anderson et al 85 paper the 
variation of mass in living animals at a given proximal limb circumferance 
varies by 
a factor of two. So all such mass estimates should show a plus or minus 
variable of 50% (this should have been done in the 85 paper which failed to 
include 
this basic scientific variable), which brings the mass estimates for 
ceratopsids within the estimated range. In other words using limb dimensions to 
estimate mass only gives very general ball park estimates and must never ever 
be 
used to restore mass for purposes that require more accurate estimates, such as 
biomechanics. 

The premise of the 85 paper is that mass correlates consistently with limb 
strength, but this is silly because animals vary enormously in structural 
strength. So chimps can rip apart humans of egual mass because they have far 
more 
strongly constructed skeletons operated by a much more massive musculature. As 
observed by myself and Per Christiansen, ceratopsid limbs, vertebra and even 
the ribcage are way overbuilt for animals of their mass. This is probably an 
adaptation for high speeds and combat between themselves, and with giant 
avepods. 
The volume of big Triceratops specimens such as the USNM example simply will 
not allow a mass much over 6 tonnes, about the same as similarly bulky bull 
Loxodonta which have much more slender leg bones because they are slow and 
don't 
battle tyrannosaurs. Apatosaurus also has exceptionally massive vertebrae and 
leg elements, perhaps it was specialized for felling trees to eat what it 
could not otherwise reach. Anderson et al actually estimated that the CM 
Apatosaurs weighed more than the HM Brachiosaurus. This is the sort of absurd 
result 
that should have caused the authors to reconsider their methodology, because 
the volume of the brachiosaur is obviously far greater than that of the 
apatosaur. The Anderson et al mass estimate for Apatosaurus is far too high, 
that for 
Brachiosaurus is only a little lower than mine which is a reflection of the 
elephantine strength factors of the slow brachiosaur. 

Tyrannosaurs were lean but powerfully muscled killing machines like all 
running predators, there is no way they weighed much more than my mass 
estimates, 
which are based on volumetric models rather than my life drawings. 

G Paul