Sauropod rearing (was Sauropod Energetics (Peristaltic pump))

[dinoboygraphics@aol.com]

I heartily welcome Kent's suggestion that we engage in what would 
constitute evidence for sauropod rearing or lack thereof.  I hope to 
contribute to this myself when I get back to Wyoming,  but I did want 
to point out an issue I have with the analogy regarding neurological 
control:

"[Regarding the vestibular coordination issue, ever walk while carrying 
an extended extension ladder vertically, like when you are painting a 
house, and you want to move the ladder around the corner? As the upper 
end of the ladder sways about its up to you to correct it before its 
too late. In this case you're on the ground looking up, and you've got 
a big clever head on your shoulders. In the sauropod's case, its itty 
bitty head is way up there, trying to reach something to eat while 
suspended at the end of a dynamically flexing neck that's extended 
above a swaying trunk supported by perhaps somewhat wobbly legs on 
uneven ground, and it's got to decide in real time whether the current 
degree of swaying that feels and sees is within tolerance, or whether 
its time to take a sidestep, or ...] "

I think this analogy has several flaws; first of all, the cleverness of 
my head (well, ok, pick YOUR favorite example...) is really irrelevant 
to the issue of basic neurological control.  It is not at all clear 
that EQ has the slightest correlation with  basic neuromuscular 
control; idiotic fish and snakes are perfectly graceful, while teenage 
humans can be hopeless.  In all seriousness, can anyone cite a single 
paper that correlates high EQ (which tends to be associated with 
behavior flexibility and the ability to learn new responses to novel 
situations) with locomotor adeptness?  If not, let's please end this 
pernicious myth.

While working on our (poorly articulated) Camarasaurus mount, I just 
this week had to heft a 20 foot ladder.  Despite it being made of 
lightweight aluminum, it wasn't any fun to manipulate, even with two 
people.  But, and this is key, being near ground level is not an 
advantage, but a huge disadvantage.  Why?  First of all, vertebrates 
use a number of sensory apparatus to judge balance and motion.  Because 
my organs of balance where not at the top of the ladder, I lacked the 
good physical feedback that a sauropod head would have swaying at 6 
meters off the ground.  Also, the arc at the top of the ladder (or a 
head on the end of a neck) moves much more, providing better quality 
data prior to reaching the point of disaterous disequilibrium.  That's 
just basic pendular physics.  Lacking all of this forced me to largely 
use my eyes to judge perspective, which is a far inferior method, as 
well as the relative pressure in my arms (mostly my wrists, let me tell 
you!), which are not primarily designed for that purpose.  Despite all 
of these disadvantages, I made it without dropping the ladder.

Finally, the weight of the ladder relative to the muscular skeletal 
structure supporting it was pathetic (guess I need to work out more) 
compared to a rearing sauropod.  The cennter of gravity was also much 
higher (relatively) in the system.  All of this meant I had a much 
smaller range of error I could succesfully recover from.  A 15 ton 
sauropod with 25 kg head in the air at the end of a 1 ton neck (at 
most) would have far more muscle available to correct for errors, 
especially since the neck is not dead weight (like a ladder), but 
itself had ranges of motion and muscles that can adjust posture.

I honestly cannot see how any aspect of the ladder analogy is 
physically or physiologically correct.  This in no way trivializes the 
other challenges that Kent has laid out in trying to solve the 
biomechanical issues of sauropod rearing (or lack thereof), but rather 
than being the more intractible of the two problems, I'm not sure that 
neuromuscular control is even a valid source of concern in addressing 
this issue.  I would be very interested in data that supports other 
interpretations.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: Kent A. Stevens <kent@cs.uoregon.edu>
To: rtravsky@uwyo.edu
Cc: DML <dinosaur@usc.edu>
Sent: Thu, 26 Jan 2006 21:19:07 -0800
Subject: Re: Sauropod Energetics (Peristaltic pump)

Sauropod discussion frequently uses the elephant as an analog for 
rearing, and the giraffe as an analog for the neck. But the sauropod 
bipedality story will be far more difficult to resolve than the 
sauropod neck story (which "only" involves osteology and a reasonable, 
non-naive estimation of cartilage, at least to reconstruct an 
undeflected neck). 
 
Now we'll need to quantitatively estimate muscle moments, the center of 
mass for the portion of the skeleton that is engaged in pivoting about 
the acetabular axis, the starting and ending poses, and more. 
 
But since it seems so hard to get simple skeletal reconstructions 
straight (sorry) for sauropods, it looks fun-but-nearly-hopeless to 
make headway on their rearing up. 
 
Would anyone want to help lay out some ground rules on what would be a 
convincing (if not overwhelming) argument either for choosing between 
the two (mutually exclusive) alternatives: 
 
1) that (at least SOME) adult sauropods engaged in feeding bipedally 
(or tripodally) 
 
or alternatively: 
 
2) NO adult sauropods engaged in bipedal (or tripodal) feeding. 
 
My question is not which is your answer (1 versus 2) but what would be 
a convincing argument for nailing either alternative. 
 
To be constructive, let's please separate the problem into biomechanics 
(which is testable for a range of bracketed estimates) and the neural 
command-and-control coordination issue (which I suspect will be far 
more difficult to resolve). 
 
[Regarding the vestibular coordination issue, ever walk while carrying 
an extended extension ladder vertically, like when you are painting a 
house, and you want to move the ladder around the corner? As the upper 
end of the ladder sways about its up to you to correct it before its 
too late. In this case you're on the ground looking up, and you've got 
a big clever head on your shoulders. In the sauropod's case, its itty 
bitty head is way up there, trying to reach something to eat while 
suspended at the end of a dynamically flexing neck that's extended 
above a swaying trunk supported by perhaps somewhat wobbly legs on 
uneven ground, and it's got to decide in real time whether the current 
degree of swaying that feels and sees is within tolerance, or whether 
its time to take a sidestep, or ...] 
 
and 
 
[Oh, and rearing up for mating is just not the same problem (as we all 
know). Sauropods could rear up to mate as if partaking in a bit of 
mountain climbing, engaging the pollex claw as a crampon, and anyway 
the entire weight of the male need not be maintained in static 
equilibrium during the mounting. For a sauropod (or an elephant for 
that matter) to sustain a bipedal posture for even a few seconds is 
significantly more demanding, and all for a lot less gain, seemingly.]