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Re: Diplodocus: Return to the Swamps????
--- On Sun, 12/13/09, Dann Pigdon <email@example.com> wrote:
> From: Dann Pigdon <firstname.lastname@example.org>
> Subject: Re: Diplodocus: Return to the Swamps????
> To: email@example.com
> 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:
> 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.
> 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
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/
> Bipeds also had the option of walking plantigrade with
> their ankles flat to the mud, for which there
> is trackway evidence:
> 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...