From: swf@teradata.com (Stanley Friesen)
Newsgroups: talk.origins
Subject: Re: Holden and the long-necked sauropod II
Date: 5 Oct 92 19:49:13 GMT
Reply-To: swf@tdat.teradata.com (Stanley Friesen)
Organization: NCR Teradata Database Business Unit

In article <718230634@sheol.UUCP> throopw@sheol.UUCP (Wayne Throop) writes:
|
|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.)

Indeed, it is quite likely that the nuchal ligament strength exceeds that
of pure elastin.  One of my books (perhaps Alexander's) goes into considerable
detail about how connective tissue is usually a composite material that
combines the benefits of the various components in mutually synergistic
ways.  Thus a ligament, not being pure elastin, would tend to be reinforced
with other materials.

|
|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. 

Many disagree with McGowan, he is hardly speaking for paleontologists in
general in his book.  (Which is not even a scientific monograph or textbook,
it is a popularization, with all the dramatization usual in such books).

|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. 

Now *this* is a true scientific source - in fact this is *the* current
summary reference on dinosaurs (it is a monographic symposium).
It make *no* concessions to popularization.  I would take this books
postion over McGowan's any day of the week. (Though I still reserve the
right to disagree with it when I feel it appropriate to do so).

|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.   

Hmm, doesn't this sound familiar?  I think I have being saying the same thing.
(And while I have read McGowan's book, I did not remember this particular
section).

|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.

The possession of gizzards is, in my opioinion, quite strongly supported,
there are a number of cases of apparent gizzard stones in fossil sauropods
(sufficiently well documented to be convincing to me, given thier close
realtionship to birds).

And, oh yes, the most likely reason that the sauropod ancestors dropped down
to all fours from a bipedal stance was because of the weight of the gigantic
digestive tract.

|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)). 

See above.  Large digestive tract => longer intestines.
-- 
sarima@teradata.com			(formerly tdatirv!sarima)
  or
Stanley.Friesen@ElSegundoCA.ncr.com