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Archaeopteryx Chimaera

Message text written by INTERNET:luisrey@ndirect.co.uk
>Since Archaeopteryx evidently does have a dinosaur skeleton and a dinosaur
pelvis and theoretically should have had (in Ruben's theory) a diaphragm
and the hepatic piston of a crocodile(?) does that mean that Archie IS NOT
a bird and IS NOT in the bird lineage?<

        What I can't quite grasp is why Ruben et al. are insisting that a
hepatic-piston respiratory mechanism is incompatible with an evolutionary
scenario leading to an avian-style respiratory system.  Doesn't the
presence of pleurocoels and other traces of a pneumatic system in
_Archaeopteryx_ (as well as other theropods) indicate that one _can_ have
both a heptic-piston style respiratory system (as evidenced by the position
of the pubis and the liver) as well as an avian-style one?  I fail to see
why the presence of features of both types of systems isn't indicative of
transition from one to the other as well as evidence that both could (and
were) used in tandem.  Can someone clear this up?

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                     Jerry D. Harris
                 Fossil Preparation Lab
          New Mexico Museum of Natural History
                   1801 Mountain Rd NW
               Albuquerque  NM  87104-1375
                 Phone:  (505) 899-2809
                  Fax: ; (505) 841-2866