It was a large herbivore that could reach over 9 metres long and weigh over 5 metric tons, and were able to move as a biped and a quadruped. Three species are universally recognized: P. walkeri (the type species), P. tubicen, and the short-crested P. cyrtocristatus. Additionally, a fourth species, P. jiayinensis, has been proposed, although it is more commonly placed in the separate genus Charonosaurus. Remains are known from Alberta, New Mexico, and Utah, as well as possibly Heilongjiang if Charonosaurus is in fact part of the genus. The genus was first described in 1922 by William Parks from a skull and partial skeleton found in Alberta.