Re: Swiming spinosaurus

["Mickey Mortimer" <Mickey_Mortimer11@msn.com>]

Steven Coombs wrote-

> I heard and read about the "hump theory", and I do find somethings wrong
> with this theory, how could an animal have something like this on its
back.
> There would be too much weight distributed on the back of the animal, the
> animal would be a struggleing with it whnever it moved! From the remains
of
> the neural arches they were quite slender(It would be really imposible to
> hold it up much), and if it did have a hump, would it be more plauseable
> that it would have had air-sacs just like some giant Sauropods such as
> Sauroposeidon in there neck, to take off a bite of the weight? And why do
> they bring this up more on Spinosaurus than other animals presumed to have
> sails such as Ouranosaurus, and it lived on the same continent as
> Spinosaurus and the same type of environment? Aleast Ouranosaurus has
> remains while Spinosaurus remains just dust!

I strongly suggest you read Jack Bailey's (1997) paper on the subject.  He
performed biometric analyses showing the spines of most sail-backed
dinosaurs are similar to those of humped mammals, mostly artiodactyls.  This
means the narrowness is not an issue.  Remember that most theropods were
rather laterally compressed, so the hump would not have been much more
hindering than the whithers of a bison (which in some extinct species like
Bison antiquus actually equals Spinosaurus in neural spine height).  Of
course, Spinosaurus was probably bipedal, but it could have had very robust
limbs, an elongate tail for counterbalance, or even have been partially
quadrupedal, as spinosaurids do have robust and elongate forelimbs.  Bailey
examines all types of humped dinosaurs, including Spinosaurus,
Acrocanthosaurus, Rebbachisaurus, Ouranosaurus and Barsboldia.

Bailey, Jack Bowman, 1997, Neural spine elongation in dinosaurs:
sailbacks or buffalo-backs?:  Journal of Paleontology, v. 71, no. 6, p.
1124-1146.

Mickey Mortimer