From: rh@smds.com (Richard Harter)
Newsgroups: talk.origins
Subject: Dinosaur necks
Date: 7 Sep 92 04:54:34 GMT
Distribution: smds
Organization: Software Maintenance & Development Systems, Inc.


I did some back of the envelope calculations on the weight, center of
gravity, and torque of the neck of a large dinosaur.  To get a handle
on things consider whoppersaurus whose neck was 6 feet across at the
base of the neck and 2 feet across at the head.  If we approximate this
by a cone we get a center of gravity of 10 feet and a volume of 400
cubic feet.  Using 60 lb/cu ft gives us 24000 lb.  However necks aren't
conical -- there is an exponential taper.  Correcting for this gives
us more like 8 ft and 16000 lb with a torque of 96000 lb-ft.

A neck weight of 8 tons for a whoppersaurus [~180 tons] is a bit more
than I expected.  Ted Holden suggested a center of gravity of 15 ft
and a weight of 30000 lb, for a torgue of 450000 lb-ft.  As can be seen,
Ted's numbers are on the high side, but they aren't ridiculous.  I
suspect he ignored neck taper.

-------------

I happened to have McGowan's book and Bakker's book out at the same
time and did a cross comparison of arguments about necks.  It makes
for interesting reading; the points they address are very different.

McGowan goes into the blood pressure issue at considerable length.
Giraffes have necks about 10 ft long; they have high blood pressure
and a lot of adaptations to handle it.

An odd point, which I hadn't thought of, is that an elevated neck is
much less of a problem that long legs.  The reason for this is that
the return path is down hill in the neck and up hill in the legs.

The movement of blood against gravity can be aided by arterial muscle
wall pumping.  McGowan concedes this, but doesn't put too much faith
in it.

Bakker really doesn't deal with the issue. so I assume he takes the
view that there must have been adaptations and it's no big deal.

McGowan makes the point that diplocoids had ossification of the
ligatures that limited vertical neck motion to 30 degrees.  This is
more than it seems -- a 30 ft neck could raise 15 ft.

Bakker makes the point that diplocoids had heads at right angles to
the neck, which implies that the neck was upright at the head.

Bakker also makes the point that long necks held out horizontally
don't make sense evolutionarily, i.e. there is no advantage in having
a long neck if you can't use it.  It occurs to me that there is an
advantage in having a long neck, even if it's not lifted, because
it can be moved from side to side, i.e. an animal can graze on a
a large area without moving.

McGowan makes much of the sedate life style and the deliberate movements
of elephants.  He concedes that elephants can stand on two legs but
doesn't believe that sauropods could.

Bakker argues that sauropods like Diplodocus and Apatosaurus, which
had longer rear legs could rear up and stand on their hind legs, but
that Brachiosaurs, which had longer front legs, didn't.

Neither brings up mounting behaviour, which I think settles the question.
Baluchetherium [the largest known land mammal] was as big as a small
to moderate size sauropod.  In order to mate the male has to mount the
female, i.e. it has to be able to rear up on its hind legs.  It may not
have to maintain the posture unsupported very long but it has to be able
to do it.  I'll buy Bakker's side of the story on this one.

-------------

It is very easy, when one is reading a persuasive author like Bakker or
McGowan, to buy into their arguments.  Sitting down and comparing authors
side by side is refreshing; it reminds you that a lot of inferences are
being drawn from very sparse material.  And it is impressive that there
can be a meaningful and legitimate argument about the life style of an
animal that lived a hundred million years ago.
-- 
Richard Harter: SMDS Inc.  Net address: rh@smds.com Phone: 508-369-7398 
US Mail: SMDS Inc., PO Box 555, Concord MA 01742.    Fax: 508-369-8272
In the fields of Hell where the grass grows high
Are the graves of dreams allowed to die.