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Re: Size limiting factors (rib cages)



Ken Kinman (kinman@hotmail.com) wrote:
 
<Is there a scientific term for "bird-like ribcage"?>

  _Bathystethic_, I'd guess. _Saurostethic_ might be the
opposing one, for "lizard-chested." Someone tell me if the
recent Greek rheko- ("shallow") is appropriate as a stem?

<And if it is an Avetheropodan (Neotetanuran) characteristic, is
this kind of bird-like ribcage also found in Therizinosaurs or
not?>
  
  Elongation of the mid-dorsal ribs over the anterior ribs
occurs in *Yangchuanosaurus* (*Metriacanthosaurus* is something
else, but probably is a carnosaur), and tyrannosaurids, more
strongly than in other non-avian theropods, and more posteriorly
in the series. *Alxasaurus* does not preserve a complete ribcage
(no therizinosauroid does) but enough shows the the posterior
series had longer ribs than the mid series did; the mid-series
is elongated (but not to the degree in other taxa) in
dromaeosaurids, oviraptorids, troodontids, *Archaeopteryx,* and
*Compsognathus.* What we know of the rib cage of spinosaurids
comes largely from *Baryonyx* and inferrences from other
tetanurans; the condition appears to be similar among
*Sinosauropteryx* and ornithomimids, and *Baryonyx*, and how
this correlates with Carrier and Farmer's hypothesis of pubic
breathing has not been tested. Longer pubic boots do appear to
occur in animals with deeper middle ribs, but with relatively
reduced prepubic processes, and this is true of
therizinosauroids. This can be correllated into the size of the
gut: the chest is shallower in longer-booted forms, and the
pubic boot in tyrannosaurids is otherwise transformed by being
set at an angle to the shaft, and the shaft is mesopubic.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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