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Gastroliths and Lung Ventilation






>Crocs do carry gastroliths, and not just for ballast!  Radiographic 
studies
>in the 1970s showed that they aid in the digestion of meat (break up 
small
>bones in things like rats).
>

    
     Croc gastroliths are in the posterior portion of the body cavity, a 
result of the vertical division associated with the hepatic-piston 
diaphragmatic lung ventilation system. Now bird gastroliths and gizzards 
are more anterior ( see where I'm going?). Now then we have a putative 
theropod dinosaur, Protarchaeopteryx, with gastroliths in the body 
cavity: does anyone with better pictures of the thing than me tell 
whether the gastroliths are anterior or posterior? Because  _if_ 
Protarchaeopteryx is a theropod and  _if_ the gastroliths are anterior 
then the claims that all theropods had a hepatic-piston do not apply for 
at least one group of non-avian dinosaurs.

 WMattTroutman 

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