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Re: Pubic Pendulum



To Michael Skrepnick:

I'm not debating whether theropods used their pubic
boots to rest on. I'm saying that it could have a dual
purpose and greatly increase stability when large
carnivores attacked their prey. If T. rex had no boot,
and was struck by a frightened hadrosaur or attacked
by another of its own species, it would be easier for
the beast to topple over from the force of impact.
Have you ever seen that bicycle on TV which rides
across a suspended wire with a pendulum beneath it?
Well, i've heard that trackway evidence suggests many
theropods walked in a bird-like one foot in front of
the other style - analogous to the bike on the wire.
Maybe it increased stride efficiency over great
distances....which would be helpful if you were a T.
rex following the migration of hadrosaurs. As for the
small propubic species with somewhat short tails like
the Oviraptorosauria, i'm not sure. They probably
relied more on their primary/retrice feathers for
stability. BTW, wouldn't the leg muscles need to be 
flexed when sleeping/resting to reduce stress on the
pubic shaft? If they weren't, total body weight would
be transferred to the pubis, possibly the ischium, and
the tail. This gets me thinking about the role of
gastralia in suspension of the thoracic portion of the
body. Maybe the reason we see co-ossified gastral
elements in Giganotosaurus is because the weight of
the head, neck, shoulders, and rib cage were being
placed partially on the gastralia and then to the
pubis. This could also be the reason some of these big
theropods have large neural spines....they act as a
suspension bridge to help reduce the dorsoventral
stresses on the centra/zygapophyses while resting. In
fact, I think the "pectoral" or "cervicodorsal" neural
spines of G. carolinii have been enlarged....possibly
to make its upper body rigid? The thick neural spines
of T. rex could probably do the same, and may be one
of the reasons that species adopted a more compact
frame. Your thoughts on this? 

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