Re: Diplodocus: Return to the Swamps????

[don ohmes <d_ohmes@yahoo.com>]

--- On Sun, 12/13/09, Dann Pigdon <dannj@alphalink.com.au> wrote:

> From: Dann Pigdon <dannj@alphalink.com.au>
> Subject: Re: Diplodocus: Return to the Swamps????
> To: dinosaur@usc.edu
> Date: Sunday, December 13, 2009, 10:39 PM
> Here's a good reconstruction of what
> a theropod foot looks like going into and coming out of mud,
> 
> courtesy of Stephen Gatesy:
> 
> http://www.brown.edu/Administration/News_Bureau/1998-99/98-123g.html
> 
> It goes in splayed with plenty of resistance (limiting the
> depth of penetration), but is drawn out with 
> converged toes that offer far less resistance. 

All true. But again you miss the reality of a swamp. There is a depth at which 
the theropod is helpless and can be simply run over.

> Sauropods,
> on the other hand, would have had to 
> fight each step to extract a foot from deep mud. That's
> bound to tire a large animal out after a 
> while.

In deep mud, there isn't real extraction in the sense that the foot clears the 
surface. The foot is lifted, and moved forward _through_ the mud. Only large 
animals can do it at all, and the larger you are, the easier it is to do in a 
given mud. Longer legs (absolute, not relative length) have more leverage, and 
can reach deeper bottoms. Toes are not helpful. Again, you can experiment w/ 
this yourself.

> Bipeds also had the option of walking plantigrade with
> their ankles flat to the mud, for which there 
> is trackway evidence:
> 
> http://paleo.cc/paluxy/elong.htm
> 
> It would have been awkward, but would have provided even
> more surface area to prevent sinking 
> in the first place.

Again, we are taking the sinking case. Going _over_ a deep swamp* (the 
non-sinking case) isn't an option for multi-ton cursorial bipeds, especially 
after thorough turbation and mixing by much larger and longer-legged quads. 
Going through one (the sinking case) is where large quads excel. After a period 
of time, a swamp would become thoroughly sauropod-ized, and certain failure for 
any large theropod.

Now I am out of time. Being a longtime Swamp Thing fan (I lost #1 in a house 
fire), I have no answer to the elegant arguments of Lee Hall, but will answer 
any comments that show a modicum of thought when time permits... which will be 
later in the week, or next weekend.

*chest-deep on a man or deeper...