Protorosaurs were formerly considered to be the ancestors of lizards, but phylogenetic analysis has subsequently verified that they are in fact non-archosaur archosauromorphs. As originally defined, the Protorosauria referred to the group containing "Protorosaurus" and "Prolacerta", and was synonymous with the "Prolacertiformes". In 1997, Nour-Eddine Jalil conducted an analysis of the "Prolacertiformes"; this analysis expanded its definition to include 14 genera, including the Tanystropheidae. Subsequent research has generally found that "Prolacerta" is closer to the Archosauriformes than "Protorosaurus", making the "Prolacertiformes" non-monophyletic. Whether the remaining protorosaurs – including "Protorosaurus", tanystropheids, and drepanosaurs in some studies – form a monophyletic group is unclear. Different phylogenies have supported both monophyletic and non-monophyletic Protorosauria, with the latter arrangement generally having "Protorosaurus" as being more basal than the Tanystropheidae.