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Re: Pubic Pendulum

Michael Skrepnick informed us in his original message
sent today (February 05, 2001 10:29 PM) on the
subject of Re: Pubic Pendulum

>...My understanding of theropod
trackways is that at a slower gait the tracks are offset from each other
forming a classic bipedal "zig-zag" pattern but that as the trackmaker moves
faster the separation between left and right footfalls draw in closer to the
midline as speed and momentum moves the animal forward.<

    This is true, indeed, and evidence of it is found in ichnological
literature.   My personal (but amateur) experience of examining dinosaur
trackways of various sizes in Arizona, Maryland, and Texas also seems to
bear this out.

  Michael Skrepnick (same communication) also said:

<Back for a moment to the pubic boot issue.  The question I have is that
other then functioning as a rest support system, what other evolutionary
advantage is to be gained in possessing a distally expanded boot, while many
of the more primitive theropod lineages ( comprising both large and small
animals ) seem to have gotten along fine without it?<

    What follows is my somewhat hesitant contribution toward that question
its partial answer?). This might seem 'way out in left field' -- to put it
conservatively :) -- but, I wonder: Could (in females only, of course) one
useful function of the pubic boot have been to provide support and/or
positional stabilization (and, maybe, to 'measure' spacing relative to the
nest's edge ridge) for the animal during egg laying? [I have noticed that in
some dinosaur nests, the eggs seem to have been very precisely laid out,
side-by-side, with long axes radial from the nest center, around and just
within the nest's circumference.]  Michael Skrepnick and other persons on
this list know a lot more about dinosaur skeletal anatomy than do I, so I
ask such persons whether this idea seems parsimonious with what is known.

    Thanks in advance for your insights pertinent to my question.

    Ray Stanford