The large reptile tree recovers pretty much the same nesting, but nested Anningsaura betweenSimosaurus and Pistosaurus, just off the taxon list of Benson et al. (2012). However, the large reptile tree does not include Bobosaurus (Dalla Vecchia 2006), a pistosaurid taxon without a known skull. I wonder how Anningasaurus would have nested in Vincent and Benson’s analysis after adding Simosaurus and a few other basal sauropterygians?
Vincent and Benson (2012) thought the palatal elements did not contact one another and the nasals were not identified. Using DGS I can see the nasals are premaxilla are (at worst) fused together, so they are all still present and need to be scored that way. In their conclusion Vincent and Benson (2012) emphasized the lack of contact between the pterygoids and considered this the most reduced ossification among plesiosaurians. If true, this would be an autapomorphy in a clade that otherwise has a solid palate (Fig. 2).
However, lack of skull fusion is an ontogenetic feature of juvenile skulls in plesiosaurs, according to Vincent and Benson (2012) and I’m out of my league here judging ontogeny in plesiosaurs. However, the large size of the skull, relative to the basal relatives of Anningasaura argues against a juvenile assignment, I would think.
The complete reptile family tree is here.