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Re: Long Bone Scaling in Neosauropod Dinosaurs



Andreas Johansson writes:
 > > And yet isometry or near-isometry is much more common in limb bones
 > > that we'd naively expect.  McNeill Alexander, for one, has repeatedly
 > > made the point that the long bones of elephants are proportionally
 > > more gracile than those of much smaller rhinos and hippos.  The
 > > interpretation seems to be that large animals simply move much more
 > > carefully than smaller ones: they don't need to be athletic since they
 > > don't need to deal with all that dangerous messing about with predator
 > > avoidance that constrains smaller animals.
 > 
 > Do hippos suffer more from predation than do elephants?

I doubt it, but have no data.

 > Photage of lions killing and eating, not necessarily in that order,
 > healthy adult elephants caused something of a stir a couple of
 > years ago - I cannot recall hearing of any predator taking down
 > equivalent hippopotami (humans excepted).

That doesn't contradict the hypothesis that I (very tentatively!)
advanced abover: it could be that hippos are that "big enough" point
where getting bigger no longer requires l^1.5 scaling in limb-bone
diameter.  But, hey, this is not exact science.  At all.

Guy Leahy writes:
 > So what about those titanosaurs which possessed armor?
 > Would they have needed armor if they were immune to
 > attack by predators by size alone?  Would titanosaur
 > scaling depart from isometry as a result?

That would be several more layers of inference than I would want to
base a guess on.

That said, it would be cool if someone took the measurements and
figured it out.  I guess the expected result, if any, would be that
limb-bone isometry sets in for armoured titanosaurs at smaller sizes
than it does for other sauropod clades.  Problem is, most (all?)
sauropod clades have all their members so big that you might never see
any allometry at all -- which indeed seems to be the result of the new
Bonnan paper.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor    <mike@indexdata.com>    http://www.miketaylor.org.uk
)_v__/\  Everything is not lost.  It's probably just down the back of
         the sofa.