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Re: Refurbished Berlin Brachiosaurus Mount



Kent A. Stevens writes:
 > > me that Stevens and Parrish's ultra-low neck posture of Brachiosaurus
 > 
 > "ultra low" ???  <insert indignant puffing sounds here>
 > 
 > Is 6-7 m "ultra low"?

It's all relative, Kent.  For you or me, 7m would not be bad going;
for a Brachiosaurus it's pretty feeble :-)

 > Please check out my website (at least look at the pictures) at:
 > 
 > http://www.cs.uoregon.edu/%7Ekent/DinoMorph/Brachiosaurus/index.html

Please believe that I am _very_ familiar with your web-site and
publications!

 > A range of 3D body reconstructions are show that are dimensioned  
 > based on what information is explicitly available in Janensch and  
 > Riggs.

The problem, as I'm quite sure you don't need me to tell you, is that
all the crucial information for neck posture is missing from Janensch
and Riggs, since it's missing from the specimens.  The only published
brachiosaur specimen that preserves _any_ of the cervicodorsal
transition or any part of the mid-to-posterior cervical series is HMN
SII, which is missing all the neural arches from C9 backwards.  So we
can't begin to postulate the range of motion allowed by zygapophyseal
articulation.  Even if the method is correct and reliable for
Diplodocus and Apatosaurus, it simply can't be applied to
Brachiosaurus.

So that leaves the far less informative technique of articulating the
centra (which BTW are distorted) in the way that seems to best
position each condyle within the preceding cotyle.  That is really not
a lot to go on; even if we assume that we can ignore the centrum
distortion and that the intervertebral cartilage was insignificant, at
best all we learn is _a_ posture that the animal could adopt.  And
it's hardly surprising that the near-horizontal neck posture was
possible since otherwise poor Brachiosaurus would not have been able
to get between a the low-head position it would have needed to adopt
for drinking and a putative high-bowsing position.

In summary, the fossils just don't tell us enough to be able to say
anything more than we could have said a priori.

 > Next, if one is interested in the osteology of the vertebral series
 > in the cervicodorsal region, check out the composite I made of
 > Janensch's illustrations (on that web page above) and compare with
 > various artistic interpretations.

Sorry, Kent, but your composite _is_ an artistic interpretation.
There's nothing wrong with that, but it really doesn't have any more
weight that Matthew's or Janensch's or Paul's or Czerkas's or Wedel's.

 > Or, better, just wait until new material with more complete neural
 > arches becomes available to "lower the boom".

Now that is a strategy worth pursuing :-)  If only we could _do_
something about it, though!

 > If it turns out the towering Berlin interpretation turns out to be
 > supported by new material, that'd be so cool.  The "ultra low" 6-7
 > m head height configuration just doesn't fit our time-honored
 > expectations for a proper Brachiosaurus.

OK, but remember those time-honoured expectations got that way because
Matthew and Janensch made it so, and they were not total dummies.

 > Time will tell.

No argument there, anyway :-)

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  "There was a time when nostalgia wasn't so popular.  Those were
         the days" -- Ian Ridley, writing in the _Observer_