I've done a bit of digging to find out the situation regarding "Nyasasaurus". Because George mentioned that Mike Benton suggested the remains were non-dinosaurian, I contacted Mike. He said that he looked at the specimens in the BMNH a while ago and he didn't think any could be confidently assigned to the Dinosauria, though they are archosaurian. He suggested I speak to Angela Milner, who has a student studying the remains. Unfortunately, Angela replied that the study is just beginning, so there is no news to report as of yet. Looks like we'll know what "Nyasasaurus" is eventually. Now to track down Charig's dissertation....