Re: Sauropod Necks

[Stanley Friesen <sarima@friesen.net>]

At 08:49 AM 7/12/00 -0700, Matthew Bonnan wrote:
> Stanley Friesen said:
>
> > Elephants have been seen rearing up to get at foliage.  This sort of
> > behavior is not that energy intensive with an animal like _Diplodocus_ with
> > a properly placed center of mass.
>
> Elephants do, on occasion, rear up to reach foliage.  For reasons I have 
> previously outlined, we don't know for sure that Diplodocus and other 
> sauropods could rear up on their hindlimbs.  How do you know that tripodal 
> rearing in a sauropod is "not that energy intensive"?

*Assuming* that the center of mass is correctly placed relative to the 
hips, it takes relatively little leveraged power to lift the body 
weight.  I don't know this is the case.  It is one more particular detail 
that be checked to see if rearing to feed is a reasonable hypothesis in 
diplodocids.


> For the long necks: if sauropods are descendants of animals like 
> prosauropods (a very sticky systematics issue still!), perhaps becoming 
> bigger gives you a longer neck that later becomes exapted for more 
> efficient feeding, but perhaps these weird dinosaurs didn't evolve a long 
> neck initially for feeding purposes.

Actually, the case for using the long neck for feeding is quite strong for 
prosauropods.  These animals were more clearly capable of standing up to 
reach higher foliage.

It is possible that the long necks in sauropods are in a sense relicts of 
their prosauropod-ish ancestry, which have been co-opted for some other 
purposes in the larger animals.

>   Evolution often works by producing structures that are later adapted to 
> new functions -- there is often the temptation to assume that the 
> evolution of various structures is guided purely by "need."

Quite so.  I even alluded to this possibility with regard to _Apatosaurus_.

--------------
May the peace of God be with you.         sarima@ix.netcom.com