"P. gobiensis" is named for the region it was found in 2001, and first described by Sereno, Zhao and Lin in 2010. It is known from a skull and partial articulated skeleton with gastroliths. Many other specimens either cannot be determined to belong to any particular species, or have not yet been assigned to one. These specimens are generally all referred to as "Psittacosaurus" sp., although it is not assumed that they belong to the same species. More than 200 specimens of "Psittacosaurus" have been found in the Yixian Formation, which is famous for its fossils of feathered dinosaurs. The vast majority of these have not been assigned to any published species, although many are very well preserved and some have already been partially described. Nearly 100 "Psittacosaurus" skeletons were excavated in Mongolia during the summers of 2005 and 2006 by a team led by Mongolian paleontologist Bolortsetseg Minjin and American Jack Horner from the Museum of the Rockies in Montana. Although only "P. mongoliensis" has been described from Mongolia so far, these specimens are still in preparation and have not yet been assigned to a species.