Re: sauropod rearing

["Kent A. Stevens" <kent@cs.uoregon.edu>]

Regarding GSP's:

> All sauropods had to be able to rear. At least the boys did. To  
> have sex. So
> what the fuss about? Rear to have sex. Rear to eat. Not much  
> difference when
> you think about it.

Actually, there are significant differences when you think about it.   
I had mentioned a few days ago:

> Oh, and rearing up for mating is just not the same problem (as we  
> all know).  Sauropods could rear up to mate as if partaking in a  
> bit of mountain climbing, engaging the pollex claw as a crampon,  
> and anyway the entire weight of the male need not be maintained in  
> static equilibrium during the mounting.  For a sauropod (or an  
> elephant for that matter) to sustain a bipedal posture for even a  
> few seconds is significantly more demanding, and all for a lot less  
> gain, seemingly.

Climbing up to mate, perhaps requiring several attempts until the  
forelimbs are placed up and over the back of the female, then  
settling the male's body mass over the female's back once mounted, is  
way different from shifting from a quadrupedal to a bipedal/tripodal  
stance without the aid of a partner to climb up, then, trying to  
balance and hold that posture.

This discussion is helping underscore that intuitions are not enough,  
that there is utility, for instance, in computing and tracking the  
instantaneous center of mass during hypothesized bipedal postures,  
for a variety of sauropod body plans and postures.

Kent