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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.


--Mike H.

* 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.