From: swf@teradata.com (Stanley Friesen)
Newsgroups: talk.origins
Subject: Re: Friesen on elastics and sauropod necks
Date: 2 Oct 92 20:46:12 GMT
Reply-To: swf@tdat.teradata.com (Stanley Friesen)
Organization: NCR Teradata Database Business Unit

In article <42@fedfil.UUCP> news@fedfil.UUCP (news) writes:
|In article <1150@tdat.teradata.COM>, swf@teradata.com (Stanley Friesen) writes:
|
|*On what evidence do you base this conclusion?
|
|Several varieties of evidence:
|
|1.  We no longer have such creatures, and there must be a reason for that.

The *most* one can conclude from this is that *something* has changed.
It gives *no* indication of *what* that something is.  It certainly fails
to rule ourt ecological shifts, or the possibility that mammalian anatomy
predisposed them to a diffrent size range.
|
|2.  The only creature with a neck even remotely similar to a sauropod's in
|    our world is the giraffe, and he holds his neck up for two very good 
|    reasons:  to lessen the torque stress, and to get at high leaves.  The
|    strength of these two motives would have been vastly greater for a
|    sauropod.

What evidence do you have for the *first* of these reasons?
[That is, give me references in a refereed journal].

Considering that I, and others, have seen giraffes with the neck held
straight out, I suspect that there is no evidence for the supposed torque
limit.

|3.  Simple calculations, as I have noted, show an impossible strength
|    requirement for a sauropod to hold his head out vertically in our
|    world, perceived gravity being what it is now.

And as we have pointed out *repeatedly*, *strength* is irrelevant, that is
what the neck ligaments were for.

|*And *I* repeat, they have concluded that *some* (not all) sauropods held
|*their necks out horizontally because that is how the bleeping bones *fit*
|*together.  Brachiosaurus is still modeled with a *vertical* neck, because
|*that is how *its* bones fit together.
|
|Brachiosaurus would have no less of a problem getting blood to his brain
|than any other sauropod, given our perceived gravity.  The facts regarding
|this, as put out by McGowan and others do not respect persons.  Brachiosaur
|is only being modeled with his neck vertical by people who either have not
|read or do not believe in the recent literature.

Show me one statement in any refereed journal, or in a serious scientific
symposium, which indicates a reconstruction of brachiosaurids with a
horizontal neck.  In my *extensive* reading of the current literature
(including a copy of the massive, monographic, "The Dinosauria"), I have
*never* seen brachiosaurids reconstructed in any manner except with a
vertical neck.  And I have almost never seen diplodicids reconstructed in
any way *except* with a nearly horizontal one (even as far back as Bakker's
197? article in Science that blew the aquatic sauropod concept away).

|In reality, of course, brachiosaur HAD to hold his head up to get at the
|leaves he fed on.  Getting blood to his brain was no problem due to the
|attenuated gravity of the antique world.
|
|*You are *still* getting diplodocids and brachiosaurids mixed up!
|
|You're the one mixed up.  The height requirements for the two kinds of
|saurs (getting blood to a vertically held head) would be entirely
|similar.  ANd, if the heart needed to do this would not fit in a
|brachiosaur, it certainly wouldn't fit in the smaller diplodocus.

The heart necessary would fit with no trouble, as long as the sauropods
had giraffe-like assists in the neck arteries.  Look at Norman's recent
reconstructions of Brachiosaurus.

|*Treated as a rigid bar, with a single lever point.
|*Treated as a flexible chord, with a distributed load support, the
|*results are quite different.
|
|Even a suspension bridge has a center of gravity.

True, but said center is *irrelevant* to the structural integrity of said
bridge - which depends solely on the ability of the individual supports to
hold up the portion of the weight suspended from them.  (Well, I am ignoring
shear stresses caused by vibration and twisting, since they are not relevant
to the issue at hand).

|*Rubber bands are *not* living tissue.  Living tissue has this nice little
|*property called self-repair.  It is only after death that ligaments undergo
|*degradation.
|
|Death from the kind of stress you're claiming these creatures took for
|granted would come within a few days at most.  There'd be no time for self
|repair.

In the absence of evidence, this is an absurd statement.
|
|*The leaf level depends on the type of vegetation.   Since the best
|*reconstruction of the Morrison environment are of a rather dry, seasonal
|*environment, with tall trees restricted to water courses, I think that
|*you are probably wrong here.  (The envoronment was dry enough to have
|*desert style dried lake beds - playas).
|
|Again, reread what McGowan says about the lives of elephants.  They spend
|most of their waking hours eating;  McGowan says it is not clear to him
|how anything could eat enough to get any bigger than elephants.  

I do not have my copy of McGowan (?sp) handy, but I suspect that this is
taken out of context.  This argument certainly only applies to *endotherms*,
a cold-blooded animal would need less food at any given size.  And guess
what, the sauropods are the *only* group of dinosaurs that the recent
evidence shows were cold-blooded.

And this *still* does not address the leaf-level issue.  In a dry habitat,
with most of the leaves at a relatively low height, a long vertical neck
would *not* be of much use.  (Actually, the different neck arrangement
in sauropods were probably a form of resource partitioning, where each
type ate leaves from a characteristic height range, and where, due to the
dry, open nature of the habitat there were leaves available at most height
levels).

|Digestive efficiency has to be another sort of a square/cube problem in 
|that it has to be related in some way to surface area of intestines, 
|which will go up as a square.  The digestive efficiency of sauropods was
|not likely greater than that of elephants.  

Probably not, but thier calorie requirements per pound almost certainly
were *much* lower. (Calories per pound goes *down* the larger an animal
is, and is about an order of magnitudde lower in cold-blooded than warm-
blooded animals).

|If elephants require huge amounts of lush vegetation, than sauropods were
|not going to deserts or environments devoid of tall trees.  The long necks 
|figure to have been an adaptation to eating leaves precisely from tall
|trees.
|
True, to a degree.  This is whay the earliest sauropods were ones with the
neck held relatively high.  The diplodocids, with their horizontal necks,
where a relatively *late* group, clearly derived from ancestors with
elevated necks. (I am talking about the cetiosaurid/camarasaurid lineages
that can be traced back to the Early Jurassic, compared to the Late Jurassic
or later age for all known diplodocids).
-- 
sarima@teradata.com			(formerly tdatirv!sarima)
  or
Stanley.Friesen@ElSegundoCA.ncr.com