The Psittacosauridae were a group of ceratopsian dinosaurs. The family Psittacosauridae was first named by Osborn in 1923. The first exact definition as a clade was in 2005 by Paul Sereno: the stemclade consisting of Psittacosaurus mongoliensis, Osborn 1923, and all species more closely related to Psittacosaurus than to Triceratops horridus, Marsh 1889. The group consists of basal ceratopsians from Asia living during the Lower Cretaceous. The only other known genus is Hongshanosaurus.