Psittacosaurus major is from the lower beds of the Yixian Formation near Beipiao City in Liaoning Province. P. major, named for the large size of its skull, was described by Sereno, Zhao and two colleagues in 2007. Known from a nearly complete skeleton with a skull, it appears to be about the same age as P. lujiatunensis. You and colleagues described an additional specimen and concurred that it was distinct from P. lujiatunensis.
P. major is characterized by a proportionately large skull, which was 39% of the length of its torso, compared to 30% in P. mongoliensis. The type skull measures 20.3 centimeters (8 in), longer than the 19.7 centimeter (7.75 in) femur. These bones are larger than the type of P. mongoliensis but within the size range seen in that species. In addition to its large size, the skull is characterized by an extremely narrow snout and jugal 'horns' which are longer than in any species except P. sinensis, P. lujiatunensis and P. xinjiangensis. The 'horns' are angled slightly downwards instead of directly outwards as seen in those species. The flange on the dentary resembles that of P. meileyingensis but is even more prominent. Although its contemporary P. lujiatunensis also had a large skull, P. major can be distinguished by general proportions: P. major had a long narrow skull, while P. lujiatunensis had a broad skull.
Read more about this topic: List Of Psittacosaurus Species