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Re: SICB Report



Huge amount of e-mail today, far more than I can respond to before it all goes
stale. Meanwhile--

In a message dated 1/18/99 11:28:21 AM EST, th81@umail.umd.edu writes:

<< In Makovicky & Sues and my own, Therizinosauroidea is the sister group to
 Oviraptorosauria; in Sereno's, it's the sister group to Ornithomimosauria. >>

Naturally, the problems with finding a place for Segnosauria (or
Therizinosauroidea) within Theropoda arise because segnosaurs most likely
aren't theropods. I've been all over the character matrices for _Alxasaurus_
and _Erlikosaurus_, and I haven't found a single feature that unequivocally or
even strongly supports a theropod origin for segnosaurs. Instead, segnosaurs
exhibit a random collection of derived features, some of which occur in
coelurians, and these features are typically bistate characters (usually
present/absent) whose appearance in segnosaurs need have nothing to do with
their appearance in one or another theropod group.

Best place for segnosaurs in the dinosaur family tree seems to be as derived
members of a clade that includes certain small prosauropods, such as
_Thecodontosaurus_, _Agrosaurus_, _Azendohsaurus_, _Anchisaurus_, and the
like. Many segnosaur features not found in other theropods occur among such
prosauropods.