Re: sauropod arm articulations

["Matthew Bonnan" <mbonnan@hotmail.com>]

In response to G. Paul:

"Contrary to Bonnan's implications, I never implied that sauropod's did not
have straight limbs, as anyone who is familiar with my research and
illustrations of 25 years knows. I've always emphasized the elephantine 
posture of
sauropod legs. In responding to Bonnan's implication in the JVP paper that 
sauropods
and all land giants must have straight legs, I noted that joint morphology 
as
well as limb proportions show that many giants had or have flexed legs
suitable for true running with all feet of the ground."

But Greg, I _never_ say in my paper that all land giants have straight legs. 
 You are talking about something that is not the focus of my paper.  What I 
do say is: 1) bone is strongest when loaded in compression; 2) graviportal 
mammals such as elephants assume a columnar limb posture during the support 
phase; 3) it is reasonable on this basis to assume sauropods were doing 
something similar.  I grant you that some large mammals have flexed limbs, 
but what are we talking about here?  You seem to think that I am saying that 
sauropods have straight legs because they're giants -- I never say that 
anywhere in my paper.  In fact, I even talk about how titanosaurids may not 
have had totally straight legs (sensu Wilson and Carrano, 1999).  My paper 
is about a possible mechanism for developing a U-shaped manus, not whether 
big animals have to have straight legs.

"Sauropod legs were not
straight because they were gigantic, but because they were slow. Sauropods, 
like
elephants, could not achieve a full run, and probably could not exceed an
elephantine 15 mph, which is a very low top speed."

Again, not the focus nor intent of my paper.  You are distorting what I say 
in my paper and why I say it.  I was simply trying to delimit forelimb 
position during the support phase, not to make an overall generalized 
statement about what it means to have straight legs.

"Bonnan claims that in the 87 DPP paper I strongly crossed the radius and 
ulna
of Brachiosaurus. Not so, as seen in Fig 3, in fact I show the same partial
cross over as in Bonnan's Fig 9 of Apatosaurus. The brachiosaur lower arm
articulations are based on the excellent Berlin material and are correct, 
and
pretty much the same as Bonnan's results. And his and my elbow articulations 
are
the same."

Greg, you and I are going to disagree on this, so I am politely stating that 
I have seen the Berlin material first-hand and your conclusions and my 
conclusions are different.  Enough said.

"Last year I noticed the SVP abstract on supposedly horizontal scapulas in
sauropods and went to the presentation to see what was up, or not. The 
scapula
pose actually shown was 45% above horizontal, the maximum protracted 
position of
sauropod scapulas, and therefore within the acceptable range and not at all
subhorizontal."

Define subhorizontal, because you and I are talking past each other.  30-45 
degrees IS subhorizontal to me, as opposed to say 90 degrees or more which 
is what is seen in some other reptiles as you say.  And, again as stated in 
my paper, I angled the scapular blade at approximately 40 degrees from 
horizonal, aka, subhorizontal.

"The scapula was
positioned much more vertially than in Wilhite's not excellent motion 
studies
of sauropod arms, which actually shows the elbows flexed!"

Wow -- that deserves no comment except to say that Wilhite doesn't deserve 
it.

"Which they certainly
were not for the reasons described by myself, and Christiansen, as well as
Bonnan (except possibly for titanosaurs in latter's opinion)."

Greg, I would appreciate the courtesy of at least acknowledging that I am 
not simply opining the limb position in titanosaurs or other sauropods.  
Again, I discuss why I coming to certain conclusions in my paper.

"The basic posture of the scapula is not directly dependent on the existence
or nonexistence of shoulder girdle mobility, since the scapula is 
subvertical
whether or not it can move in walking tetrapods."

Greg, when I have said this?  I brought up shoulder motion in my paper 
simply to address that it might occur but that it would not effect the 
conclusions of my study, which were about manus orientation and shape, _not_ 
sauropod locomotion per se.

"Bonnan suggests that sauropods
are somehow different so maybe their scapula posture was different from 
other
tetrapods."

When do I ever say or suggest this?  Can you quote me on that?

"This has no testable content."

Right, except I didn't say that sauropod scapular posture was different 
because they are different -- you did.  If one reads the paper, my 
explanations as to why I posed the scapula the way I did are clearly 
explained.

"There is no logical reason why
sauropods would have horizontal scapulas and subvertical sternal elements 
when
other walking quadrupeds of widely varying postures, speeds and sizes have
subvertical blades and horizontal sterna, and horizontal scapulas are only 
found in
specialized nonwalkers such as diggers and fliers."

So, evolution is logical?  Are you again arguing for parsimony here?

"The sauropod shoulder
glenoid is directed strongly ventrally when the scapula is subvertical, if 
the blade
is horizontal then the glenoid faces much more anteriorly than in required
even for a vertical armed animal"

Again, please see the paper.  What you call subvertical I apparently call 
subhorizontal.  I never said the scapular blade was horizontal.

"Bonnan said things about horse wrists that shows he does not understand how
they work."

Did I not say I didn't understand how horse wrists work?  I told you that I 
have never articulated a horse wrist and was interested in how you arrived 
at your conclusions.  Thanks for implying I am stupid.

"A chronic problem with the supposed science of
paleobiomechanics is that people are doing lots of analysis and coming to
lots of conclusions about fossil taxa without out first doing basic research 
to
see what is actually going on in living animals, work that should have been
done long ago."

It is a shame that we are all so chronically short-sighted.

"The partial disarticulation of equine wrist carpals is figured in
Ellenberger's classic study of the anatomy of the horse, they obviously have
to disarticulate an extreme amount as the wrist flexes 120 to nearly 180
degrees. Someone is going to have to do x-rays to see exactly what is going 
on."

First it was "massive disarticulation," now it is partial.  Do you actually 
mean hyperflexed?  That I could understand.  Disarticulation generally means 
the joints physically come apart from one another.  Hence my previous 
question where I "said things about horse wrists that show [I do] not 
understand how they work."

I don't understand how you can criticize people for not doing the basic 
research, and then turn around and lament that someone should do x-rays and 
figure out what's going on.  Why are you not doing this basic research (I 
don't mean horse wrists, I mean in general)?

So I'll tell you what.  My research stands for what it is.  It is certainly 
never going to be perfect, but my hope was to put my alternative hypothesis 
about sauropod manus evolution out there.  If you want to continue to 
criticize it be my guest.  What I would welcome at this point were actual 
discussions of particular specimens, data on articulations, models, etc., 
that point in a different direction or contradict my observations and data.  
In fact, I suspect that when more information about basal sauropods becomes 
available, I may be changing my hypothesis.  But that's how science works 
and I welcome it.

I end my discussion here with you on this or any other topic, at least for 
the near future.  I can't in good conscience continue to discuss this with 
you because I am disappointed by how flippantly you disregard other people's 
hard work or how easily you chastise others for admitting their ignorance.  
I certainly acknowledge that your publications and artwork took skill and 
effort even if I may not agree with your conclusions -- it would be nice if 
you extended others the same courtesy.

Matt

Matthew F. Bonnan, Ph.D.
Department of Biological Sciences
Western Illinois University
Macomb, IL 61455
(309) 298-2155
mbonnan@hotmail.com
MF-Bonnan@wiu.edu
http://www.wiu.edu/users/mfb100/

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