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Re: Removing segnosaurs from Theropoda



In a message dated 95-08-29 18:33:52 EDT, jdharris@lust.isem.smu.edu (Jerry
D. Harris) writes:

>        That is correct, as per your BCF theory.  But that was also _my_
>point:  if the interdental plates extend back to the lineage that presages
>theropods, prosauropods, and therizinosaurs, then you can't, as Thom Holtz
>pointed out, use interdental plates as a synapomorphy for just the
>prosauropods and the therizinosaurs -- instead, it's a symplesiomorphy
>that's shared in both those groups _plus_ the Theropoda.  Now, as you did
>clarify, "small interdental plates with respect to tooth size" could be a
>synapomorphy, if the ones in theropods are considered different...but I'd
>like to know what the primitive condition (the one possessed by the common
>ancestor of birds, theropods, prosauropods, and therizinosauroids) was
>before I'd be satisfied with a label of whichever later condition as a
>synapomorphy.

And you can't use it as a synapomorphy uniting segnosaurs and theropods,
either, as Clark et al. do. Hence my careful use of the words "may be" in my
original posting.

Incidentally, the more I look at the mandible of _Erlikosaurus_, the more
convinced I become that had it been discovered in Triassic deposits, it would
without hesitation have been referred to Prosauropoda.

G.O.