Re: Jobaria and the Elephant Commit Suicide

["Matthew Bonnan" <mbonnan@hotmail.com>]

Wow!  First of all, I am again amazed at yet another neat dinosaur from 
Sereno et al. and it was neat to see the pics at the meeting and now on the 
web -- anything that pushes our knowledge on sauropods further is of course 
the best way to spend our money. =) =P  Now, onto the rearing up sauropods 
...

Dan Varner said:
It seems to me that it would take about a day for a carnosaur to learn that
> > when a large sauropod BEGAN to rear up on its hind limbs that that would 
> be a
> > signal to come and get it. "Here's my exposed belly and hind limbs!"No 
> big
> > deal for those swift killers to avoid that kind of confrontation. I'm 
> sorry,
> > but I don't think this scenario has been thought out very well. There is 
> no
> > mention at the www.jobaria.org website about elephants using this kind 
> of
> > behaviour for defense. Have I missed something?

No, I don't think you have -- elephants usually use their massive heads and 
tusks, but then again sauropods got small heads, so you could argue, I 
guess, that they resorted to foot stomping.

Richard Travsky adds:
> AN elephant merely provides a physical model for the behavior.

Okay, but here we must be extremely careful.  Despite all the functional 
stuff I could throw in here about elephant skeletons differing from 
sauropods (and you would all sigh and kill me), what elephant are talking 
about?  African, Indian, what species, what geographic range?  It is very 
easy to go from using an elephant as a useful yardstick to jumping to 
conclusions about specific behaviors.  Just because Jobaria or other 
sauropods "look" like they're designed to rear up doesn't mean they did, 
whatever you compare them to.

Richard Travsky adds further:
> Don't forget, rearing up gives the impression of being larger. Many
> animals do the equivalent - like raising fur or having a mane.

Err, okay.  But remember we are dealing with very huge animals here -- they 
are already big and weird.  Why mess with them in the first place -- how 
much bigger and scarier do you need to be?  You can step on or kick a 
dinosaur which comes close without the rearing, and some sauropods have what 
appear to be tail "weapons": whiplash in diplodocids, clubs in shunosaurs 
(unknown/unsure in other Chinese forms).

Again, the rearing model is interesing, but remains to be tested: there is a 
big tail muscle (caudofemoralis) that runs off the tail and inserts onto the 
fourth trochanter of the femur about half way down in sauropods.  No matter 
how you choose to have them rear, something has to happen with this 
connection -- no good answer so far, from me or anyone else who studies 
these beasties, so that is not a criticism, just something to note.

While I will be the first to tell you sauropods have strong hands and limbs, 
the thought of all the weight crashing back down gives me the willies!  I 
don't care how much cartilage you stuff in there, I don't think the rearing 
and falling on your enemies thing would work too well.  A more controlled 
descent, maybe, but then we'd need to look at what muscles and ligaments 
controlled that descent.

Sauropods are weird, huge, and wonderful without having to make them 
something bigger, better, and faster.  We still barely understand the 
anatomy of these huge animals, and it will be a while before many of these 
scenarios can be rigorously tested.

Matt Bonnan
Dept Biological Sciences
Northern Illinois University
DeKalb, IL 60115

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