From: throopw@sheol.UUCP (Wayne Throop)
Newsgroups: talk.origins
Subject: Holden and the long-necked sauropod II
Summary: none of Ted's points are actually supported by the people he quotes
Date: 04 Oct 92 23:39:40 GMT

Basically, Ted claims three effects related to neck size would prevent
sauropods from existing under modern conditions.  Blood pressure
necessary from vertically-held necks, required forces to support
horizontally held necks, and finally the amount of food needed to
support their metabolism.  (The digestive efficiency issue is vaguely
related to the neck, in that the neck is supposed to be a device for
reaching food sources unavailable to other animals.)

Further, Ted claims that "scientists" agree with him that no plausible
solutions are known to exist for these problems (other than the Famous
Holden Lesser Felt Effect of Gravity). 

The problem is that "scientists", both those Ted quotes and those he
does not, in fact do NOT agree with him on any of the three above
points.  Ted (at best) must selectively quote and creatively
misinterpret to reach that conclusion. 

Below is what the "scientists" have to say for themselves about these
points, in various books available in the library I have available to me. 

: From: news@fedfil.UUCP (news) (Ted Holden)
: Message-ID: <42@fedfil.UUCP>
:: Message-ID: <40@fedfil.UUCP>
:: The reality is that nothing of flesh and blood could hold the torque 
:: involved with the notion of holding a sauropod neck out near horizontally.

I've already shown some calculations that refute this claim.  But Ted
doesn't have to take my word for it, here's what McGowan has to say from
_Dinosaurs_Dragons_and_Sptifires_ in 1991. 

    Many sauropods have neural spines that are prominently forked in
    in the neck and anterior dorsal regions, and these probably acted
    as a guide for a massive nuchal ligament.

Here's what Alexander has to say from 
_The_Dynamics_of_Dinosaurs_and_Other_Extinct_Giants_ in 1989.

    I am going to suggest that these necks were supported in the
    same way as the necks of horses, cattle, and their relatives.
    These animals have a thick ligament called the ligamentum
    nuchae running along the backs of their necks.  Unlike most
    other ligaments it consists mainly of the protein elastin,
    which has properties very like rubber.

Alexander then goes on to calculate that the strain that could be
taken by the nuchal ligament is sufficient to support sauropod necks.
(He gives max stress for elastin as about 200 newtons/cm^2, and the
calculation I did the other day requires more.  But certainly *some*
form of ligament would explain even the most severe cases: ligament
strengths go up much farther than 500 newtons/cm^2.)

::: From: swf@teradata.com (Stanley Friesen)
::: Message-ID: <1150@tdat.teradata.COM>
::: [..scientists..] 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.

References to this literature would be appreciated.  Ted has claimed
several times that a heart large enough to produce the required blood
pressure "wouldn't fit in a sauropod body".  McGowan argues against
Bakker's notions on grounds of blood pressure, and mentions that
blood pressure of 568 mgHg would be required.  But he nowhere says
that such blood pressures are impossible.  The only thing he mentions
as impossible in this connection is:

    The idea that sauropods reared up on their hindlegs, raising their
    heads even higher than their necks allowed, can be dismissed on
    the grounds of blood pressure problems alone.

Others disagree with him (especially on the subject of the importance of
arterial pumping), but even if he's right, that does NOT rule out
sauropods on all fours extending their heads straight up due to blood
pressure problems.  He's only ruling out sauropods rearing up on their
rear legs. 

Here what Alexander has to say:

    It would be a mistake to argue that a blood pressure of 8.5 meters
    of water would be impossible because it is so much higher than the
    blood pressures of modern animals.  If giraffes were unknown, that
    kind of argument would lead to the conclusion what giraffes were
    impossible.

And specifically on the issue of how large the heart would need to be,
we do have _The_Dinosauria_ by Weishampel, Dodson and Osmolska, 1990. 

    Seymore (1976) predicted that sauropod hearts would have to undergo
    myocardial hypertrophy by a factor of eight (conservative estimate)
    in order for the ventricular wall to sustain stresses of 500 mgHg
    in the absense of hydrostatic support.  What are the limits to
    exygenation of the myocardium?  How could the respiratory system
    tolerate the burder of dead air space in the elongated trachea?
    [...]

Desmond (1976) discusses problems with heart pressure, but only in
conjunction with the now-discarded "snorkel" interpretation of the
sauropod neck.  So, I see no sign that there is any consensus that blood
pressure problems in brachiosaurs were an insurmountable problem. 

Again, if Ted maintains there IS such a consensus, he ought to be
able to produce references to *some*body who holds that opinion.

: From: news@fedfil.UUCP (news)
: Message-ID: <42@fedfil.UUCP>
: 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.  

Ted simply reads McGowan too carelessly.  Here's what McGowan says:

    African elephants spend about 75-80 percent of every 2wenty-four
    hours feeding, so in terms of their food requirements they would
    appear to be close to the maximum size permissible for a mammalian
    herbivore living in Africa today.

But far from being "not clear to him how anything could eat enough to
get any bigger", he proposes a solution in the very next paragraph. 

    Although we cannot guarantee the correct solution, it seems likely that
    the answer probably lies in the area of gut efficiency.  The elephants
    digestive tract has a high processing rate; its droppings contain large
    amounts of undigested food.  Other mammalian herbivores, including the
    ruminants (animals that chew the cud), have more efficient systems, and
    can obtain more nutrients from their food.  Though Baluchitherium, being
    a rhinoceros, was not a ruminant, it seems that it must have had a more
    efficient gut than that of the elephant.  Even so, it is difficult to
    imagine that Baluchitherium would have had much time for anything else
    besides eating. 

So it is patently false to claim that it "isn't clear to" McGowan how
larger animals can exist on these grounds.  He gives ways to do it in
the very book Ted references. 

Further, remember that McGowan's agenda in that whole passage is to
argue against Bakker's hot-blooded metabolism notions.  McGowan advances
the other obvious way out of the problem of not enough food: he proposes
that the metabolic rate of the sauropods is lower than that of modern
mammals.   

Alexander gives tables in his book showing that even with lower
metabolism than mammals, sauropods are large enough that they could have
maintained high body temperatures.  In fact, he devotes an entire
chapter to the issue of metabolic rate, and concludes that there isn't a
definitive way to choose between Bakker et al and McGowan et al in the
matter of metabolic rate.  One reason being that there are other ways to
increase digestive efficiency. 

: From: news@fedfil.UUCP (news)
: Message-ID: <42@fedfil.UUCP>
: 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.  

Clearly, Ted is wrong here.  Bakker, Alexander, and many others point
out that sauropods very likely posessed gizzards, and could reduce their
food much more efficiently than elephants.  It is almost *certain* that
sauropods had a more efficient digestion than did elephants.  And, in
addition to chemical (cows and fermentation processes, along with cud),
recycling (rabbits and reprocessing of incompletely digested feces), and
mechanical (birds (and sauropods) with gizzards) methods of increasing
efficiency of digestion, the intestines could simply be made to be a
tube of the same diameter as that of the smaller animal, and so have the
absorbtion surface go up as the cube (at the "expense" of a longer, more
convoluted digestive tract (which would also increase efficiency)). 

Thus we can clearly see that Ted is wrong, both because he ignores the
fact that elephants don't have any of the three classic methods of
increasing digestive efficiency, and he uses his usual patented
uniformitarian scaling errors in making his argument. 

Not to mention that he's setting himself up against his own reference
in this matter, McGowan, who clearly states that elephant digestion
is NOT the most efficient possible.

( And of course, it has been pointed out to Ted that this is
  a plausible reason why nothing has RE-EVOLVED to larger-than
  elephant size: it's much more of a trick to change one's
  whole digestive strategy than to get a bit bigger.  Certainly,
  there is no mechanical limit as Ted supposes. )


In summary, the books written by "scientists" directly contradict
Ted as to what those scientists are claiming.  That being the case,
I contend it is more reasonable to take the scientists own word
as to what they claim, rather than Ted's.
--
Wayne Throop  ...!mcnc!dg-rtp!sheol!throopw