Apparently, Proterosuchus is not considered a basal Archosauria proper. I got the idea that it WAS thanks to my Dinosauria, 2nd Edition, but then I read on Chinleana that it's NOT. Rather, it's a non-archosaurian archosaurmorph. Makes me angry. I thought I was done with the stupid art show. So, okay readers, please point me toward an archosaur (preferably basal to the Crurotarsian-Ornithodiran split) that has an obvious antorbital fenestra and maxillary fenestra, because those are the features we're focusing on in the show's introductory text.
And hey, what's the current status of Euparkeria? According to the list of Archosauria synapomorphies in Dinosauria, 2nd Edition, it seems like that little guy would fit. Here is the list, according to the book:
1) An antorbital fenestrae;
2) The postfrontal reduced to less than half the dimensions of the postorbital or absent;
3) An ossified laterosphenoid;
4) The prootic midline contact on the endocranial cavity floor;
5) Teeth with serrated margins;
6) A lateral mandibular fenestra
Since Euparkeria has features 1, 5, and 6, I'm guessing it lacks features 2, 3, and/or 4. I was surprised to learn that the fourth trochanter is diagnostic of a more inclusive group and thus not a synapomorphy of the Archosauria, proper.