bipedal lunges

[wa105@mead.anglia.ac.uk]

Toby wrote:

>You wrote:
>>velocities. I like your idea of a brief charge. I've speculated and have
>>developed some restorations of Triceratops going bipedal for a step or 
>two at
>>the culmination of a charge. I think most of their offensive activity was
>>directed at each other, however.

>Dunno about a bipedal charge, but at least a bipedal lunge.  If the
>principal defensive tactics were hers-based, it wouldn't do to have a
>defender too far out of line.  But it still seems reasonable to have the
>beast rock back and up on his hind-legs, thus reducing his moment of
>inertia, then pivot, following the dodging tyrannosaur...

It doesn't seem reasonable to me, except in juveniles.  A typical 
ceratopian had a heavy head and a long body, so its centre of gravity was 
well forward of the hips.  I reckon it would have to raise itself almost 
to the vertical to balance on its hind legs.  As it starts off sloping 
downwards, it has to rotate through nearly 90 degrees.

And that's a long way for the front half of the animal to jump, if you see 
what I mean.  As a rough rule of thumb, an athletic vertebrate can make a 
standing jump of one metre, whatever its size.  (Not 2m, Mr Spielberg!)  
And if we are generous enough to treat the front half of a ceratopian as 
an athletic animal, that still doesn't get it nearly high enough.  A 
hatchling ceratopian, certainly.  Adult Protoceratops, perhaps.  But 
Triceratops?  No way.

>Plausible, anyway.  I have a little trouble believing a ceratopsan could
>develop the speed, but it would't need too much.  Also, in a semi-erect
>position, he'd get a lot of mechanical advantage on the pivot, just by
>moving his head...

Sorry, I don't understand.  The pivot about what point?

                                                                Bill