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Pubic Pendulum



Hooray! I got my Predatory Dinosaurs of the World book
today.....beautiful illustrations, my hat goes off to
you, HP G.S.Paul. One thing I would like to speculate
on after reading page 118, is where it discusses the
function of the distal pubic foot of many theropods.
It says that the pubic foot could have been a "rocker"
which theropods rested upon. In restorations of
Allosaurus, Giganotosaurus, and Tyrannosaurus the
angle of the pubic foot would seem too steep to
support the animal. If you drew a line (which would
indicate the surface of the ground contacting the
pubes) from the tip of the foot to the proximal
portion of the tail it would intersect the ischia. I
suppose the distal expansion of the ischium in large
carnosaurs would help support any weight not shifted
to the pubic foot, but that of T. rex seems weak, and
the estimated 7 tonnes of theropod mass might snap the
ischium in half (which would undoubtedly make it
painful for T. rex to relieve itself). Dr. Holtz would
have to confirm this, because I haven't seen a rex
skeleton in 14 years, but it seems like a safe
assumption. But what if the pubic foot was being used
as a stabilizing mechanism in these larger theropods?
It might make them less top-heavy, and aid in faster
locomotion. In essence, a "pubic pendulum". This
effect would be even greater if the trunk was
lightened from air sacs. In small bird-like theropods
like Sinornithosaurus, the posteriorly-directed pubic
boot would make up for the weight discrepancy created
by a shortened tail. Anyway, just thought this would
make for an interesting discussion....???  

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