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Fwd: Dreadnoughtus weight calculation



>From Greg Paul...

---------- Forwarded message ----------
From:  <GSP1954@aol.com>
Date: Fri, Sep 5, 2014 at 7:21 PM
Subject: Please  forward
To: bcreisler@gmail.com


The lists do not seem to be accepting my posts even though I can read the
posted messages, so please forward --

The calculation that Dreadnoughtus was 65 tonnes is massively excessive.

The solid black ink type skeletal restoration in the main text is badly
misproportioned, with the vertebral series much too large relative to the
limbs, and the body severely overbloated -- it does not even match the of course
accurate digital version of the skeleton included in the supplementary
information. The Jackie Gleason skeletal drawing would mass something approached
65 tonnes, the mass arrived at in the paper via humerus/femur circumferance
calculations that are well know to be unreliable because their is so much
variation in mass at any given combined limb circ.

In elephants the constant of body mass to femur length in decameters
squared is about 3, in the massive gigantic brachiosaurs it is 3.5 to 4 based on
the skeletons and models.  If Dread weighed 65 tonnes the constant would be
~9, far, far higher than in any large land animal. A correct skeletal
restoration, based largely on the correct digital image in the
supplementary info,
produces a constant of 4. That means that Dread had very robust limbs for
its mass, giving it a much higher safety factor than brachiosaurs that are
well known for having slender limbs. In otherwords, we use the volume of the
life version of the animal stretched over the skeleton to estimate relative
and absolute limb strength, we never ever use limb strength to estimate mass
because that is circular reasoning disproven by the large empirical variation
in living animals.

The Dread skeleton just is not very large. A number of sauropods had, or
must have had, much longer femora. For example the heavily built brachiosaurs
with femora around 2.5 m and a constant of 3.5-4 weighed 30-35 tonnes
(that's with a rather higher specific gravity than most people tend to use these
days), so Dread with its 1.91 m femur and a mass/femur constant comes out to
28. The biggest known titanosaur published femur belongs to what is not
actually Antarctosaurus at 2.3 m. That complete super titanosaur femur announced
this year I have estimated that Argentinosaurus and similar sized but more
complete Futalognkosaurus (am using the pubis length in Lacovara et al to
size this) at 2.4 m, with constants around 4, so these  were 50 tonners. No
way Dread with its three quarters as long femur weighed any where close to
those colossi.

I have been at this sort of thing since the early 1980s. Here we are in the
2010s. There is no excuse for this. By now all researchers should know
better than to publish masses estimated from limb strength at face value, or
publishing sloppily proportioned skeletal restorations. Before making claims of
size it is required to use a rigorous skeletal-muscle etc. model to compare
the volume of a particular sauropod to that of others modeled using the
same techniques, that way it would have been obvious that not really all that
big Dread is smaller than the Berlin Giraffatitan, much less the really
titanic Argentinian titanosaurs. It would also be useful for reviewers to pay
attention to these matters, since the public does not really care all that much
about the phylogenetics but does about the size. People might want to send
the paper to me for a look at before submission. Of course had the size of
Dread been accurately presented it would not have made it so big in the
press. As it is the public has been misinformed about its mass by a
factor of two
or more, and how it is Dread is modest sized compared to the really big
boys and girls.

I will be publishing this info in the technical literature.

As for the name Dreadnoughtus. Fine in terms of being big and powerful, but
the justification for the etymology in the paper and media is technically
and historically  errant. Dreadnoughts were not defensive ships nearly immune
to attack. They were the offensive superpredators of their time, used to
hunt down and destroy enemy warsahips from dreadnaughts on down -- it was
predator versus predator, not herbivores protecting themselves from predators.
At the same time dreadnoughts were very vulnerable to being sunk, sometimes
very suddenly. The first dreadnought sunk, the Audacious in WW 1, was taken
down by a single mine. Later in that war a wee torpedo boat sunk the Szent
Istavan (that's the immobile batship that rolls over with the crew scrambling
about on the hull). In WW II the Barham was lost to a submarine (that's the
batship that's rapidly rolling onto its side when it blows up). A month
later a single bomb blew up the Arizona  -- odd because the same bombs failed to
penetrate the similarly think armored decks other batships at Pearl. Two
torpedoes from a destroyer sunk Fuso in twenty minutes. And of course the
enormous superbattleships Yamato and  Musashi  were done in by swarms of little
Avenger torpedo planes (my uncle flew in one of those at  Okinawa, but was
not in the attack on the  Y). All in all about a dozen and a half deadnaughts
were lost to enemy action.

GSPaul</HTML>