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Re: phytosaurs/parasuchians/PJ Crush

----- Original Message -----
From: "David Peters" <davidrpeters@earthlink.net>
Sent: Sunday, November 28, 2004 4:36 AM

Walker suggested that phytosaurs and proterochampsids were sister taxa.
A short cladistic analysis indicates it might be true. Any stoppers?
(.that is, any reason not to associate the two clades?)

Considering... I think... all phylogenetic work on basal archosaur(iform)s that has been done in my lifetime, I think you should pose the question the other way around: What do those two clades share, except a general croc shape and lifestyle?

But to answer your question, off the top of my head... phytosaurs are clearly inside the crown-group Archosauria, lacking palatal teeth, and inside Crurotarsi, having a "crocodile-normal" (CN) ankle. Proterochampsids are clearly outside both, retaining a row of teeth on each pterygoid and a "modified primitive mesotarsal" (MPM) ankle. (That they lack other palatal teeth, however, is considered a character state that puts them close to the crown-group.)

Sometime (next weekend?) I'll dig up the paper that describes *Yonghesuchus* and finds it as the sistergroup of the crown-group Archosauria. It has a cladistic analysis with more than the two characters I've explained here.