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From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.origins
Subject: Re: more on dinosaurs and load-bearing
Message-ID: <723@psivax.UUCP>
Date: Sat, 14-Sep-85 11:23:24 EDT
Article-I.D.: psivax.723
Posted: Sat Sep 14 11:23:24 1985
Date-Received: Thu, 19-Sep-85 05:47:49 EDT
References: <391@imsvax.UUCP>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 105

In article <391@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes:
>
>     The objection  that any  animals thigh  is wider than its calf or ankle is
>irrelevant; a ten foot wide animal with ten foot wide THIGHS is impossible.

	Why is it impossible? I see nothing *intrinsically* difficult
about it. See below for a fuller explanation.

>If you insist that the ultrasaur's thigh was only 8  feet from  side to
>side, I  will just  as logically  insist that  it was then necessarily 12 or 13
>feet  from back to front, still impossible on an animal whose body was 25 or 30
>feet long and 10 feet wide.
>
	Well, here is part of your problem. You have the beasties
measurements wrong. A Sauropod only 25 to 30 *feet* long would be the
*smallest* one I have ever heard tell of. The correct size is more
likely to be 25 to 30 *yards*, in which case a width of 10 feet would
be ridiculously thin! A width of 25 feet would be perfectly reasonable,
pehaps even a bit wider. At that width two 8 ft wide thighs would only
add up to 16 feet, or about half the total width, which is again quite
reasonable. Of course all this assumes your estimates of required
muscle mass are actually correct.

>     The notion that the dinosaurs thighs were more efficient than Kazmier's is
>simply wrong by a very wide margin...
>	(A list of speculative factors supporting this claim)

	Well, as has been pointed out, there are other factors which
point the other direction, so we have now reached the limit of
Aristotelian a priori reasoning. It is time for an experiment. The
best one I can think of is to measure a number of species of animals
of various sizes and plot the weight supported by a leg versus the
average diameter of that leg. This will produce an allometric equation
which estimates the size of leg expected for animals of various sizes.
It will be "conservative", that is it will *over*estimate the required
diameter. It then becomes a matter of extrapolating the curve to the
size proposed for the Ultrasaur, and hope that the extrapolation is
valid.(This is because *any* extrapolation beyond your data is
somewhat suspect, since the curve may change just beyond the end of
available data).
>
>....   I  further  believe  that I DID that.  There are
>several points I didn't  even bother  to mention  because I  thought they would
>occur to anyone who thought about it.  These are:
>
>     1.   The HUMAN leg being the more efficient, as demonstrated.
	Well, your "demonstration" was more an argument from
reasonability than a real scientific demonstration. In fact since you
ignored leverage, it is quite doubtful that it is correct
>
>     2.   The fact  that I  was comparing  what the human could lift when fully
>          warmed up to the load the sauropod must face when getting up  after a
>          nap, totally cold.  
	Who says a Sauropod would *get up* from a nap, like many large
animals today it would probably sleep on its feet. Also, they may well
have been warm-blooded, so they wouldn't cool off sinificantly
anyway!
>
>     3.   The fact  that I was comparing what the human could SQUAT to the load
>          the sauropod must lift OFF THE GROUND.
>
	See above, why lift?

>     4.   The fact that the  constant K  itself would  not be  as high  for the
>          sauropod as for the maximally trained human athlete.
>
	Why not? They would be constantly "training", since survival
in the wild depends on good health and adequate strength.

>     I am not going to quote  Mr. Friesen's article  here;   it is  on the net.
>Basically,  he  claims  that  a Mr. R.M. Alexander has computed "load factors",
>based on the stress that BONES can take, and determined  thereby that dinosaurs
>could function  normally in  our world.   Is there a problem with that?  Anyone
>who has watched houses being built knows how  much weight  an ordinary  2x4 can
>bear when  stood end on end.  Bones are like that in a way.  Take my own humble
>middle-aged body as an example.  I am about 6' 4",  207 lbs,  somewhat stronger
>than  the  general  run  of  my  fellow  middle-aged  businessmen,  but I am no
>powerlifter.  I have friends who are; they are  a whole  lot stronger  than I.
>Nonetheless, if I kept my back and legs straight, and two of these friends were
>kind enough to put a bar with five or six hundred pounds on it on my shoulders,
>I could  stand with  it;   the bones  would not  break.  Mr. Alexander would no
>doubt then conclude that I could function quite well at 700 or 800 lbs  (my 200
>plus the bar). 
>
	No, his conclusion would be that you have sufficient
structural leeway that you could run fairly fast without breaking your
legs. Remember, he was mainly concerned with *gait*, but an animal
that has the capability of a slow run certainly can *stand* on land.
Try running sometime, see how hard you pound your feet(and legs)
against the ground, you will realize just how much *extra* tension is
placed on your legs every stride. In fact if your support ratio is
only ~4.0 you could not even run! That is a worse ratio than an
Elephant! As a matter of fact 800/200 is almost as bad as the *worst*
of the Sauropods! I rather expect that your *bones* could stand a
whole lot more. The basic point is that the limiting factor here is
not standing on land, it is the extra impact sustained during
locomotion, and this requires structural support, not muscles. Muscles
can always be adjusted as necessary.

-- 

				Sarima (Stanley Friesen)

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