Russell and Zhao also named Psittacosaurus ordosensis in 1996, after the Ordos prefecture of the Inner Mongolia Autonomous Region. The type specimen is a nearly complete skeleton, including part of the skull. However, only the skull, lower jaw, and foot have been described. Three other specimens were referred to this species but remain undescribed. Like P. neimongoliensis, this species was discovered in the Eijnhoro Formation.
P. ordosensis can be distinguished by numerous features of the jugals, which have very prominent 'horns.' It is also the smallest known species. One adult skull measures only 9.5 centimeters (3.75 in) in length. Sereno (2010) found the species as described to be indistinguishable from P. sinensis, another small species, but suggested that additional study of P. ordosensis might reveal diagnostic features. He provisionally designated P. ordosensis a nomen dubium.
Read more about this topic: List Of Psittacosaurus Species