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Re: A few more...



In a message dated 95-09-28 13:58:31 EDT, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

>Actually, Gauthier already defined "Saurischia" as birds and all dinos
>closer to birds than to Ornithischia, and "Theropoda" as birds and all dinos
>closer to birds than to Sauropodomorpha.  Padian & May defined
>"Ornithischia" as Triceratops and all dinos closer to Trike than to birds.

I love these ad hoc definitions. Suppose there were no dinos closer to birds
than to Ornithischia, which would be the case if brontosaurs were basal to
Ornithschia instead of Theropoda, a possibility certainly not excluded by any
known cladistic analysis. And defining Theropoda as birds and all dinos
closer to birds than to Sauropodomorpha could well place lagosuchians and
herrerasaurians within Theropoda (doesn't bother me, by the way), since
there's no way any known lagosuchian or herrerasaurian was ancestral to any
brontosaur unless they magically regained pedal digit V. Likewise, the
definition of Ornithischia as all dinos closer to _Triceratops_ than to birds
does not exclude brontosaurs from Ornithischia.