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Re: Pubic Pendulum

Hi Ray,

I think your idea of incorporating the boot in terms of nesting is an
interesting idea.  Perhaps not that this is an intentional adaptation in egg
laying, but secondarily if a theropod in the process of laying her eggs is
already in a squatting position, resting on its natural "pivot" which guides
the animal as it turns within the nest and deposits eggs uniformily, it is
surely an organized  system.  It would have to be dependent upon how many
eggs constitute a "clutch" and are they deposited all at one time.  I seem
to recall that in some circumstances spiraling layers of eggs would seem to
indicate more than one egg layer having occupied the nest. Is this then a
shared occupancy during one season or return use of nesting sites over the
years.  If this is the case it seems unlikely that a second female is going
to orient herself in precisely the same location as the first did.  Other
than protecting against damage to unborn offspring in crushing its own eggs
what other incentive might there be in creating these measured rings of

Mike S.

: 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
> faster the separation between left and right footfalls draw in closer to
> 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
> 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
> (or
> 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
> 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