A new chasmosaurine from northern Laramidia expands frill disparity in ceratopsid dinosaurs

摘要: A new taxon of chasmosaurine ceratopsid demonstrates unexpected disparity in parietosquamosal frill shape among dinosaurs early their evolutionary radiation. The is described based on two apomorphic squamosals collected from approximately time equivalent (approximately 77 million years old) sections the upper Judith River Formation, Montana, and lower Dinosaur Park Formation Provincial Park, Alberta. It referred to Chasmosaurinae inferred elongate morphology. typical squamosal forms an obtuse triangle dorsal view that tapers towards posterolateral corner frill. In taxon, lateral margin hatchet-shaped with posterior portion modified into a constricted narrow bar would have supported robust parietal. represents oldest Canada, first pre-Maastrichtian been both sides Canada–US border, minimum north–south range 380 km. This morphology given unique profile experimentation signalling near origin ceratopsids reinforces biogeographic differences between northern southern faunal provinces Campanian North America.