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Re: T. rex was a 'slow-turning plodder'...
On Saturday, June 9, 2007, at 09:37 AM, Brandon Pilcher wrote:
The theropod-style skeletal elements, with their thinner walls and
larger medullary cavities (compared to mammals) probably doesn't do
much to reduce overall mass (the reason being that the overall volume
of bones tends to be greater).
Are adjustments for size taken in account here (i.e. we're not
comparing the bones of a T. rex with those of a bipedal savanna ape)?
More or less. My understanding is that the bone walls of large mammals
and large theropods* both become proportionately thicker at larger
sizes, as would would be expected from allometric constraints. I doubt
that anyone has made a reliable estimate of proportional skeletal mass
between tyrannosaurs and similar sized mammals (ie. elephants and kin),
but I strongly suspect they are quite close.
* The exception being large soaring birds, specifically marine forms
like pseudodontorns, which actually become proportionately thinner
walled at large sizes. The same trend is seen in pterosaurs (at a very
rough scale, that is). In both cases, buckling and compressive loads
are prevented and/or alleviated by use of very large internal bracing
networks. In the case of pterosaurs, at least, I doubt that the
overall skeletal mass is actually very low, even though the ratio of
bone radius to cortical breadth is low.