Choristodera is an unusual linage of diapsid sauropsids. Having evolved in the late Triassic, at the very end of the reptilian radiation that preceeded the reign of the dinosaurs, these animals diversified as aquatic animals. Their relationships with other reptiles aren't well known; some have related them to lepidosaurs, alongside sphenodontians and squamates. Others classified them as part of the archosauromorph radiation. Evidence doesn't seem to favor one group over the other in this, sharing features with both.