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Fwd: Re: Dinomorph Strikes Back!... or does it?



I'm forwarding Kent Stevens' reply to Scott  Hartman's post of yesterday. DV:


I appreciate Scott's comments very  much.  The following is protracted  
(= long-winded) and of  interest perhaps to only those who are worried  
about sauropod neck  intrinsic curvature.

First of all, I want to say that I'd be delighted if  we find a  
sauropod that in life had an upturn at the base of the  neck.  It  
would be emotionally uplifting, if not merely a pun, to  find that not  
ALL sauropods went around looking like Eeyore (from  Winnie the Pooh),  
all dejected and droopy.

So please find  wonderfully uncrushed, undistorted, sauropod  
cervicodorsal vertebrae,  put those vertebrae into articulation (and I  
mean CLOSE articulation)  with tight articulation at the centra and  
zygapophyses superimposed,  and let's see what the resultant curvature  
of the neck is.  I'm  glad to see the Wyoming Dinosaur Center is  
getting the bones closer to  articulation, but the vertebrae Scott  
shows us are still way out of  articulation at the centra, and one has  
to do some additional  visualization to try to determine the  
orientation that would arise  between successive vertebrae if they  
were as closely separated as they  would have been in life.  (Also,  
while this specimen is gorgeous,  there is some obvious post- 
depositional distortion in the cervicals in  question that prevents  
the pre- and post-zygaophyses from aligning as  they would have in  
life.)  How close is close between condyle and  cotyle?  Look at the  
intervertebral separation of articulated  sauropod cervical series as  
found in situ (like on the wall at DNM)  and there is but a centimeter  
or less between condyle and cotyle, as  would be measured deep within  
the cotyle... and careful, that tight  spacing within the ball-and- 
socket joint is not apparent when one looks  casually at the gap  
between the lateral margins of the cotyle and  condyle, for obviously  
there must be a wide spacing so that the more  cranial vertebra can  
articulate by rotating over the surface of the  associated condyle of  
its caudal neighbor.  In modern vertebrae  with opisthocoely, the cup- 
shaped socket rides closely upon the ball-shaped  condyle with little  
gap between.

Here are some comments on  Scott's contribution to the DML:

> This may all be part of the  "Dinomorph Project", but let's not  
> confuse this with computer  reconstructions done using the Dinomorph  
> software.

That's  correct.

> This is Photoshop manipulation of illustrations; frankly,  it's no  
> less "artistic" than the other reconstructions that are  lamented on  
> the same page.

I respectfully disagree, and it  is not merely a matter of personal  
taste regarding what is "art" and  what is not (or what the definition  
of "is" is :).

Composting  of images is NOT "artistic".  Granted it's something that  
can be  done with paper and scissors, like in a grammar school art  
class, but  it's NOT art.

In creating the digital composites, I used scans of the  original  
illustrations, at MOST modifying the scale of the  images  
(isotropically, to preserve proportions of the lateral views)  so they  
were iso-scale.  Then I placed them in articulation with  neutral  
position simultaneously at centra and zygapophyses.  I  introduce none  
of the subtle manipulations of the shape of the centra  as one can  
find in some side view silhouette illustrations.   Please look at the  
silhouette illustrations for Brachiosaurus (on my  website under  
Brachiosaurus, and also available in PDF form elsewhere  on the  
site).  Check for yourself the induced wedge shapes in  some of the  
illustrations.  To quote Dave Barry, "I'm not making  this up".

> Photoshop composites depend strongly on the accuracy of  the  
> illustration (sort of hard to quantify off hand...), and any  errors  
> by the original artists will be faithfully passed on in  the  
> Photoshop composites.

That is correct.  In fact,  some original artwork, such as in Hatcher,  
are not consistently scaled  (i.e. not actually 1/10 even though so  
labeled, as is apparent if one  cross-checks with the actual  
dimensions), and that can get misled when  trying to composite two  
vertebrae side views that are of different  scales.  Greg Paul got  
some snickers from the audience at the  Norman SVP showing some  
pictures of diplodocids seemingly hunting for  truffles.  The problem  
was he did not account for scale  inconsistencies within the  
illustrations, as I showed in my talk  (which followed immediately  
after) based on the same original  illustrations (I presume, at  
least:  I used Gilmore and Hatcher's  images).   You view the slides  
from the SVP talk by going to  the "selected presentations" pulldown  
menu on my site, or by looking  at the illustrations Mike Parrish and  
I published in the two recent  sauropod volumes.

When one is careful to correct any scale differences,  the Apatosaurus  
CM 3018 presacral series comes out beautifully arched  (see my  
Apatosaurus page plus the sauropod book chapters), and  Diplodocus CM  
84 comes out similarly, but something funny happens at  mid-neck (a  
truffle-hunting specialization? no, probably  post-depositional  
distortion as Mike Parrish and I confirmed at Jim  Madsen's studio by  
hand manipulating into neutral articulation the  plaster casts of  
those CM 84 vertebrae!).  Every vertebral series  I have put together  
by photo-compositing) comes out with a smooth,  straight cervicodorsal  
transition when articulated in neutral  position, even Cetiosaurus  
(thanks to illustrations from John Martin  which I have cross-checked  
with the original specimen in the UK) and  now Mamenchisaurus).

But I hasten to agree with Scott re:  "any  errors by the original  
artists will be faithfully passed on in the  Photoshop composites".   
I've therefore been careful to  cross-check those illustrations with  
the photographs, when  available.  And in lateral view, the steel  
engravings generally  match up well with the photographs.  By the way,  
the posterior  and anterior views one finds in these old monographs  
usually suffer  considerable perspective distortion, for the camera  
was close to the  subject and the nearer end appears relatively too  
large compared to  the farther end, an issue that does not present  
itself overly when  considering the lateral view.

But compare the monograph illustrations  (which are generally quite  
accurate geometrically) with some of the  whole-skeleton silhouette  
drawings where subtle distortions can indeed  create the appearance of  
neck curvature in neutral pose, such as in  the artistic renditions of  
Brachiosaurus I have analyzed  quantitatively (look at the table in  
the presentation slides from the  Bozeman SVP talk).

> Another, more intractable problem is that the  search for "wedge  
> shaped" centra in procoelous vertebrae cannot  be done simply by  
> looking at lateral views of the  centra.

You probably mean opisthocoelous, not procoelous, but  anyway:  Of  
course not, and I don't trivialize the notion of  "wedge shape" by  
only looking at centra, and moreover, certainly not  to merely looking  
at their posterior (cotyle) margins.  Again,  look at our book chapter  
illustrations, and better yet, please read  what Mike Parrish and I  
carefully wrote on the subject of determining  neutral pose  
curvature.  Those chapters were subject to careful  peer review, and  
no small amount of  a priori skepticism on the  part of some of the  
reviewers, something that only helped the  text.  Oh, and again, if we  
got something wrong in our methods or  conclusions, let's fix it; we  
are not trying to prevail, just trying  to get it straight (sorry  
about the pun).

> Mechanically  speaking, the "wedge" or "keystone" shape that causes  
> an upward  (or downward) arch arises from the articulation of the  
> centra.  Since sauropod cervical articulations are convex/concave,  
> this  cannot be ascertained simply by looking at the posterior rim  
> of  the centra.

And again, I don't just look at the posterior rim, as I  just  
mentioned.  In doing this photo-compositing, I place  multiple  
vertebrae into articulation (with condyle inserted within  associated  
cotyle).  Look at the lateral view of Diplodocus on  that page at my  
site, or look at the illustrations in our two sauropod  book chapters.

It takes considerable effort and persistence to  communicate some  
concepts, and the notion of vertebral articulation  and neutral  
deflection seems to be one that requires practical  experience, and  
not just reading words.  Take a real turkey neck,  prep it down to the  
bones, and play with the vertebrae.  If the  fact that the centra are  
heterocoelous is distracting, get some  giraffe vertebrae and go at  
it!  Giraffe necks go up because they  are wedge shaped.  Really.

For the AMNH exhibition "Dinosaurs:   Ancient Fossils, New  
Discoveries" (see AMNH under "products" menu on  the DinoMorph site)  
the AMNH very kindly CT-scanned an entire giraffe  neck and I put  
those vertebrae into articulation both in DinoMorph  (watch the movie  
showing them in articulation) and, in our book  chapter in the Currie  
Rogers and Wilson volume look carefully at the  lateral views).

> The Dinomorph Camarasaurus page credits the Wyoming  Dinosaur Center  
> as having mounted a Camarasaurus with a neck in  the horizontal  
> posture "very much in agreement with the  osteological evidence",  
> the skeleton was in fact mounted that way  because of the media  
> exposure the Dinomorph project had received.  To do so resulted in a  
> gap between the zygopopheses of the  anterior dorsals that you could  
> shove a man's thigh through, see  here:
>  http://skeletaldrawing.com/sauropods/disarticulated.jpg
>
> In light  of the unacceptability of this, we recently remounted it  
> in a  closer approximation of articulation. This resulted in an  
> upright  neck, albeit not one as upright as Greg Paul used to  
> restore. A  photomanipulation of the actual bones that was used to  
> figure out  how we had to changes the armature can bee seen here:
>
>  http://skeletaldrawing.com/sauropods/articulated.jpg
>
>  Unfortunately we were constrained to modifying the existing  
>  armature, so the bones are perfectly articulated.

I think you mean "are  NOT perfectly articulated", but continuing ...

> That said, it is much  closer now than it was in the neck-straight- 
> out position. We are in  the process of scanning all the bones into  
> 3D computer space, but  manipulation of the bones in a sand box  
> confirmed that there was  no way to keep the anterior dorsals in  
> articulation and have the  neck coming straight out at the shoulders.

Sigh... I'd suggest looking at  other specimens of Camarasaurus, and  
visit the AMNH big bone room  (AMNH specimen 5761 has two vertebrae at  
the cervicodorsal transition  that are actually fused into a straight  
line, pretty clear indication  of how they were held in life).  Then  
again, just a click or two  away on the internet, just look at the  
mount "Annabelle" (I provide a  link on my Camarasaurus page), as well  
as pictures of the CM 11069  specimen which I provide, courtesy Mike  
Parrish, along with others  specimens of this sauropod.  But maybe the  
WDC specimen is indeed  different than all the others, and maybe it  
really does indicate that  this specimen, at least, bent up at the  
shoulders when it was  alive.  That would be exciting, albeit a bit at  
odds with the  other fossil evidence for this taxon.

> Kent is doing some exciting  work, but manipulating drawings in  
> Photoshop has its own share of  error sources. It's worth pointing  
> out that it isn't simply  "artists" who have argued for an upright  
> neck posture in some  sauropods. Per Christiansen, among others, has  
> published  biomechanics arguments that support this interpretation.

There are indeed  some physical arguments for a vertical neck is over  
a horizontal neck  (basically similar to why it is easier to build a  
structure that  stacks vertically rather than one that is  
cantilevered).  I agree  with the argument.  The only problem that  
seems to rear its head  (pun again, sorry) is that the neck bones  
don't permit the desired  upright neck postures.  The devil is in the  
details,  sigh.

> Don't get me wrong, the jury is still out

Remembering  the jury's verdict on the O.J. Simpson trial and the  
Michael Jackson  trial, do you really want to use a jury as a basis  
for determining the  truth?

> on how many (if any) sauropods held their necks upright, and  if so,  
> how high. But Photoshop manipulation of drawings is no  stronger a  
> form of evidence than the skeletal reconstructions  that proceeded  
> the technique. What we really need are good 3D  data sets from well  
> preserved and complete specimens.

I  respectfully disagree.  Painstaking Photoshop(tm) compositing of   
high-resolution scans of scale-calibrated monograph illustrations is   
an independently verifiable, and hence more scientifically reliable,   
form of evidence than an artist's simplified, and often stylized,   
silhouette drawing.  I rest my case.

Kent