One nearly complete skeleton of "P. lujiatunensis" from the same lower beds of the Yixian Formation had previously been classified in its own species, "Psittacosaurus major", named for the large size of its skull by Sereno, Zhao and two colleagues in 2007. You and colleagues described an additional specimen and concurred that it was distinct from "P. lujiatunensis". "P. major" was originally characterised by a proportionately large skull, which was 39% of the length of its torso, compared to 30% in "P. mongoliensis", and other features. However, a 2013 study utilising morphometric analysis showed that the supposed differences between "P. lujiatunensis" and "P. major" were due to differences in preservation and crushing. The study concluded that both represented a single species.