Re: Largest Dinosaur?

[Mike Taylor <mike@tecc.co.uk>]

> Date: Sat, 8 Sep 2001 00:25:43 +0200
> From: "David Marjanovic" <david.marjanovic@gmx.at>
> 
> > [...]
> > Bruhathkayosaurus matleyi- 44.1 meters, 175-220 tons
> > [...]
> 
> Someone has calculated that 140 tonnes are the theoretical limit for
> terrestrial quadrupeds because then the legs have to be so thick
> that they touch.  Regarding this and how pneumatic just the biggest
> sauropods were, I'm not sure whether even the lower ends of these
> ranges are low enough.

OK, I expected someone better informed than I to leap in and reply to
this, but into the silence left by Matt Bonnan and other, I hesitantly
step ...

To the best of my limited knowledge, this kind of biomechanical limit
is an area so beset with uncertainties that we struggle to say
anything very definite.  For example, here's the abstract of Hokkanen,
J.E.I. (1986).  The Size of the Largest Land Animal.  J. theoretical
Biology 118, 491-499 --

        The upper mass limit to terrestial animals is studied using
        physical arguments and allometric laws for bone and muscle
        strength and animal locomotion. The limit is suggested to lie
        between 100 000 and 1 000 000 kg. A possibility for a still
        higher mass, in case of new adaptations, is not excluded.

Yup, the Fundametal Size Limit is here estimated at between 100 and
1000 tons!  I think the most significant thing here is not so much the
figures themselves as the order-of-magnitude difference between them.

If the last few decades or so have taught us anything, surely it's to
beware of the FSL.  Remember when aerodynamics people were saying that
the twenty-foot wingspan of _Pteranodon_ was the absolute limit for
the largest possible flying animal?  Then someone goes and digs up a
forty-foot _Quetzalcoatlus_.  Or the idea that a powered-flight bird
can't have a wingspan of more than the ten or twelve feet of a condor
or albatross ...  Er, apart from the 24-foot _Argentavis_.  (Yes, I've
probably got some of the figures wrong here, but the point still
stands!)

So given some abstract biomechanical reasoning that says no animal can
grow heavier than 140 tons, and some bones that suggest an animal damn
well _did_ grow heavier, I know which one I will believe :-)

(Incidentally, that tiny abstract is all I've read of the Hokkanen
paper.  I would _love_ to read the whole thing.  If anyone knows where
it can be found online, or would be willing to snail-mail me a paper
copy, please contact me off-list.)

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor   <mike@miketaylor.org.uk>   www.miketaylor.org.uk
)_v__/\  "Fat Charlie the Archangel sloped into the room" -- Paul
         Simon, "Crazy Love, volume II"