Reanalysis of the skull of the crested Asian hadrosaurine Saurolophus angustirostris confirms its status as a distinct species from its North American relative, Saurolophus osborni. In addition to its greater absolute size, S. angustirostris is differentiated from Saurolophus osborni by an upturned premaxillary body, a more strongly reflected oral margin of the premaxilla, the absence of an anterior notch in the prenarial fossa, a sigmoidal contour of the ventral half of the anterior process of the jugal, a shallow quadratojugal notch on the quadrate, and by a strongly bowed quadrate in lateral view. Phylogenetic analysis corroborates a sister taxon relationship between S. angustirostris and S. osborni. Saurolophus itself is characterised by a solid, rod-like crest composed of the nasals, frontals, and prefrontals; secondary elongation of the frontal and prefrontal resulting in the backwards extension of the frontal platform; a frontal platform that extends dorsal to the anterior portion of the supratempo...