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Re: dinosaur humps (was Re: A Whole Bunch Of Questions)

The first criticism on Bailey's work and as yet unchallenged (as on the
list) is that the neural spines of the dinosaurs offered as "humped" do
not bear rugose textures and nor are they thickened mediolaterally or at
least as mediolaterally broad as they are craniocaudally long, as occurs
in most "withered" ungulates, especially bovids. On the other hand, the
neural spines of *Acrocanthosaurus*, contra those of *Spinosaurus*, _do_
have rugose texturing that implies muscular development. But the lack of a
"withers" as in mammals implies these are related, as in shorter-spined
theropods, to the epaxial, parasagittal vertebral musculature. Famous
models and restorations, as in Cliff Green's, Luis Rey's, or Brett Booth's
(to the paleoart community) (of which the middle is found in Gee and Rey's
new book, wonderfully brilliant and unique! Kudos, Luis! got it Saturday),
restore this has a thickened, muscular ridge that, given the layers of
muscle and skin, would have served as a thermodynamic conductor just as
easily as one without all that musculature. A fatty hump has no skeletal
analogue and cannot be indicted or contradicted on osteological material.
Such a rugose neural spine anatomy occurs to a limitied extent in
*Suchomimus* above the hips. The neural spines of *Spinosaurus* and
*Baryonyx* as well as *Suchomimus*, do not have distal mediolateral
expansions, or broader distal ends than the mid-shaft of the spine. In
*Acrocanthosaurus* (rugose) and *Ouranosaurus* (non-rugose) the neural
spines have broadened "tables" (but this is also seen in the short-spined
*Tarascosaurus*, and has been linked in thyreophorans to osteoderm
support, however unlikely in the various unarmored theropods with the
neural "tables". While the expanded distal ends occur in mammals with
withers, they are to a more extreme degree in ungulates than in
tall-spined dinosaurs. Another tall-spined dinosaur, *Amargasaurus* (as
well as its relative *Dicraeosaurus*) lacks expanded distal ends, but
taper instead with lamina indicating extensive epaxial musculature as in
other, shorter-spined sauropods (which, as in *Suchomimus*, also are
tallest above the dorsals (with the exception of *Amargasaurus*)) but no
"hump" or narrow sail.

  It would be nice to see a published rebuttal to Bailey's theory
detailing these things. They would appear to contradict his conclusions.


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.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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