Re: Sauropod movement (long)

[Mark Hallett <marksabercat@yahoo.com>]

--- "Kent A. Stevens" <kent@cs.uoregon.edu> wrote:
> Hi Brian
> 
> There's a lot of conjecture on this issue.  You can
> find numerous 
> illustrations of some sauropods walking about
> bipedally, or sitting 
> kangaroo-style.  In 2003 I reported at the Society
> of Vertebrate 
> Paleontology Annual Meeting some results from
> modeling the required 
> cross-sectional area of the caudifemoralis for a
> bipedal Apatosaurus.  
> It's apparent on some reflection of the biomechanics
> needed, that 
> lifting the animal to an erect posture would cause
> major engineering 
> difficulties, including shear stresses on the knee
> as well as the 
> required size of the musculature.

What about the possible effect that the caudotruncus
muscle and collective dorsal spinal muscle groups may
have had in sauropod rearing? If the caudotruncus were
at least as well developed in sauropods as they might
have been in theropods(in the case of the latter,
primarily as a possible mechanism for breathing),
these paired muscles could have been capable of
exerting an antero-ventrally directed pull on the
proximal caudals(Carrier & Farmer, 2000), assisted to
a smaller degree by the action of the ischiotruncus
pair on the ischium (and possibly the whole pelvis,
assuming that in sauropods it was not kinetic), also
creating a similar direction of pull? In the case of
the dorsospinal muscle groups, these could have
exerted a caudal (backwards) pull on the anterior
trunk, since these presumably inserted along the
anterior/dorsal iliac crest, and along the dorsal
surfaces of the proximal caudals- this would in theory
work to pull the trunk up and back, since the pelvis,
kept in position by the rear limbs, would act as a
fulcrum.     

   If the
> musculature could take it,  
> then the next question is whether the tiny, tiny
> brain could have 
> integrated the required vestibular and visual input
> required to monitor 
> and integrate evidence of postural error in time for
> the animal to 
> adjust it's posture and preclude a catastrophic
> crash to the ground if 
> it were to lose its balance.

How about large theropods, which were as just as
potentially unstable? Their brains weren't that big or
complex either. Copulation must have then been a very
nervous prospect for sauropods....


  Speaking for myself, I
> just don't see it!

This may be true. However, in spite of the fact that
in dinosaurs the brain was certainly not the complex
"Grand Central Station" of body motor control that
mammalian brains are, it may still have had sufficient
ability to direct visual input to complex neural
plexes that took over much of this function (motor
control of the limbs), after getting feedback from the
eyes and semicircular canals, which are known to be
well developed in Brachiosaurus (Janensch, 1918).
These neural plexes may have been much more
sophisticated in dinosaurs, perhaps even as much as
they are in birds. 

 >    The brain just doesn't have the volume or
> morphology suggesting such 
> specialization.  There is also the requirement for
> very clever 
> maneuvering to stand up adjacent to (but not
> DIRECTLY before)  a given 
> tree, then to shift it's weight and shuffle its
> stance in order to 
> align a 6 or more meter long neck and several meters
> of bipedally 
> suspended trunk into a vertical alignment just
> before the tree.  It all 
> seems too much for an animal of such negligible
> brainpower.  And all 
> this work to just stand before one tree?  Why, when
> you could walk 
> around following a rich (but seasonal) abundance of
> lower vegetation 
> along river banks without risking the danger of
> crashing to the ground 
> from many meters above ground level?  I have respect
> that Nature does 
> not present us with animals that are needlessly
> wasteful of energy and 
> effort.  Economically, I just don't see the value
> added for sauropods 
> to walk around unnaturally, in order to direct a
> tiny head to a tiny 
> bit of food that can be reached only by taking very
> careful steps 
> moving tons of flesh with each step.

Again, I'll admit this might have might have been the
case. Why, though, do we see a retroverted pelvic
condition in some sauropods like camarasaurids and
others? This would have assisted bipedal rearing. If
we consider that the overall proportions of the pelvis
and neural spine height in the dorsal verts in
presumably obligate quadrupeds like brachiosaurids and
omeisaurs were sufficient for support, why then is the
pelvis so much more robust(i.e., proportionately large
and wide for the size of the trunk)in the smaller
diplodocoids, and why are the dorsal neurals so high? 

--Mark Hallett
> 
>  
> On Apr 1, 2004, at 11:44 AM, Brian Sass wrote:
>
> > I've been reading some of your work on the
> Dinomorph project and was
> > wondering if it is possible to tell if
> > sauropods were able to stand on their hind legs
> while foraging for 
> > food or
> > if they were limited to standing on all four
> > legs.  ( I suspect they remained on all fours ).
> >
> > Brian Sass
> > Network Support Consultant
> > eTS - Network
> > ISM Canada- 1 Research Drive Regina, Sask.
> >
> > Phone: 1 (306) 790-5217   Fax: 1 (306) 790-5320
> > Email: bsass@ca.ibm.com
> >
> 
> 



        
                
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