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Re: Re : New Tyrannosaurus paper

Thomas Miller (dexter1647@caramail.com) wrote:

<First, I don't think we have any kind of idea how "thick" or "powefull"
theropod muscle really was. We may have some muscle impression on bones,
but only the ones in contact with the bones, and thus a very small
percentage and argueably not from the species here (?).>

  Of course, and all true. But one must also note that muscles of
particular size, mass, etc., also leave particular types or sizes of marks
on bones. The thigh, hip, shin, and ankle musculature studied by
Hutchinson and Garcia all leave specific correlates on the bones that
relate to other taxa and mass of these muscles can be calculated from the
size of the attachments. This is one manner in which muscle size can be
calculated, and the study is plausible by extension. So far, this is one
of the few studies that have tried to estimate _mass_ of muscle, rather
than position and effect, which Hutchnson himself has been doing for
years, as has Steve Gatesy before him, Romer and Coombs on other archosaur
hips, and a few other major studies. Russell did study on similar
ornithomimid hips, as well.

<Second, as far as I know, theropod iliums are truly exagerated when
compaired to actuall animals. Only the smallest land animals have such
exagerated iliums (e.g Felis domesticus, at least). The also state that
poor runners have less than 5% of their mass in leg muscles and 10%+
equals good runners. Truth is, that is according to OUR standards, modern

  Actually, birds of all types have very, very large ilia. Many advanced
quadrupedal dinosaurs, like titanosaurs and ankylosaurs, have very large
ilia, but are still not considered swift runners.

<Was a 20-30% of mass even possible, say common 65 million years ago ?
Nobody really knowns.>

  It is in some birds well over 30%, and such osteological features that
indicate mass in these taxa indicate that similar values were present in
cursorial theropods, like *Tyrannosaurus*.

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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