Saurischia

[gator@mail.utexas.edu (c. brochu)]

Regarding sauropodomorphs and ornithischians -

Saurischians share a number of derived states not seen in ornithischians.
Among these are elongate cervical vertebrae and an enlarged claw on the
thumb.  This comes from work by Jacques Gauthier, who published it in a
California Academy of Sciences memoir in 1986.

Incedentally, you cannot unite sauropods and theropods on the basis of the
orientation of the pubis.  This is a primitive character state that they
share with virtually all other nonavian reptiles.  In this regard,
Ornithischia is diagnosed by the presence of a back-turned pubis, but the
saurischians merely retain the ancestral forward-pointing pubis.

regards, chris




__________________
Christopher Brochu
Department of Geological Sciences
University of Texas at Austin
Austin, TX 78712
512-471-6088

gator@mail.utexas.edu


You know how it feels when you're leaning over on a barstool and almost
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