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Sauropod threads ...



Hi all:

First off, let me say it's been great talking with all of you on
these various sauropod threads.  Second, I notice that I ask for
references, but provide little of my own, so please ask me to clarify
with references if need be, and I'll work on doing that myself in the
future.

Sauropod rearing is indeed an interesting topic, and I came into
sauropod studies hoping I would find THE CHARACTER that would show,
definately, that sauropods did indeed rear up and did so often.  Hey,
a rearing sauropod would be impressive and scary to see - I get chills
just standing underneath the Barosaurus at AMNH.

However, then I started to ask, where is the physical evidence?  And
I started to realize that very little has been done to quantify or
even just model rearing in sauropods.  So, this is why I am skeptical
about sauropod rearing, I suppose.  Not that it wouldn't be possible,
but that HOW it happens must be investigated further.

Dr. Shoshani has published several papers on elephants (I've cited
one at the bottom of this posting), and from both reading his studies
and seeing elephant skeletal material, I can "testify" that elephants
are both marvelous mammals but in many cases poor sauropod models. 
The paper I cite below has nice skeletal and musculature pictures for
elephants, something you don't normally get to see.  For anyone
interested, take a look at the elephant limbs and feet, and then use
one of the many dinosaur books or articles on sauropods to compare
them for yourself.

I think you will come away with an uneasy feeling - elephants and
sauropods are really different!  And, how did sauropods walk, let
alone rear up?  One of the biggest problems with sauropod limbs is
that they do not have well-ossified articular surfaces, meaning that
much of their joint capsules were formed of cartilage.  This is
different from elephants (and all other mammals) which have
well-formed joints and simply "apply" a venear of cartilage to the
joint capsule.  This means we can get a really good idea of how much
motion was possible in fossil mammal limbs, and only, if we are being
generous, a poor idea of how much motion is possible in sauropod
limbs.

Some other things to consider - sauropods (and all known dinosaurs)
don't have patellae (knee caps), have simplified and strange wrists
and ankles (their ankles are essentially one bone, the astragalus,
with this tiny calcaneum (under the fibula) thrown in as an
afterthought), and have essentially solid limbs.

Why I am telling you all this?  Because of the above-mentioned
sauropod anatomy, it is difficult to tell how sauropods walked, let
alone rearing up on their hind legs.  But, I have no doubt that
someone will eventually model and quantify the sauropod rearing
problem, and perhaps at some point we'll have a much better
constrained idea of how well sauropods could rear.  Hence, my
skepticism of sauropod rearing for now.

Hope these posts are helpful, and I sincerely appreciate all the info
you folks have sent me.  And remember, none of us has all the answers,
so keep the suggestions on sauropod rearing going.

Reference:
J. Shoshani. 1996. Skeletal and other basic anatomical features of
elephants.  In J. Shoshani and P. Tassy, The Proboscidea: Evolution
and Palaeoecology of Elephants and Their Relatives. New York: Oxford
University Press.

Sincerely,

Matt Bonnan
Dept. Biological Sciences
Northern Illinois University