A new species of Chasmosaurus (Dinosauria : Ceratopsia) from the Dinosaur Park Formation of southern Alberta

Chasmosaurus irvinensis (sp. nov.) is distinguished from other species of t his genus by the possession of a broad snout, absence of a brow horn (the p osition of which is occupied by a pit or rugosities suggestive of bone reso rption), broadly rounded and open jugal notch, subrectangular squamosal, st raight posterior parietal bar bearing 10 epoccipitals, eight of which are f lattened, strongly curved anterodorsally, and nearly indistinguishably coos sified to their neighbours, and small, transversely oriented parietal fenes trae restricted to the posterior portion of the frill. This species, restri cted to the upper part of the Dinosaur Park Formation, is significantly you nger than the other recognized Canadian Chasmosaurus species, C. belli and C. russelli. Phylogenetic analysis shows that C. irvinensis is most closely related to the other Canadian Chasmosaurus species and more distantly rela ted to Chasmosaurus mariscalensis from Texas.