Re: phytosaurs/parasuchians/PJ Crush

[David Marjanovic <david.marjanovic@gmx.at>]

----- 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.