Re: late night thoughts: misunderstand what?4

[Dann Pigdon <dannj@alphalink.com.au>]

don ohmes writes: 

> It is reasonable to assume the large bipeds had to be careful about their footing. Eg, how steep a grade can a 2m human climb without using the hands? Not very. Also, soft ground must have been a huge problem. If you don't believe it, go for a hike in a swamp, without using your hands. There may have been large areas of refugia that were available to quads in many environments. In other words, a basic quadruped vs biped advantage.

I suspect that theropod feet (with their large spreading toes) were much 
better suited to 'soft ground' than the compact feet of sauropods (of any 
size). Whether you're a biped or a quadruped doesn't really come into it. 
Sure, a quadruped may be spreading it's weight over more points of contact, 
but a sauropod foot would have plunged into soft ground at a much faster 
rate than the foot of a large theropod would. As long as the biped lifts 
it's feet before they sink too far, it should be fine (and having just two 
feet decreases the amount of time between steps). 

A sauropod (even with less weight on each foot) would have plunged to the 
knees/elbows well before it could have lifted each foot. In fact, if the 
sauropod walking style was like that of an elephant (with at least three 
feet in contact most of the time) then they'd be even more prone to sinking, 
since the time lag between placing a foot down and lifting the same foot up 
again is even longer. 

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Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.soffiles.com
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