Original Paper


, Volume 101, Issue 6, pp 505-512

First online:

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

  • Michael J. RyanAffiliated withDepartment of Vertebrate Paleontology, Cleveland Museum of Natural History Email author 
  • , David C. EvansAffiliated withDepartment of Natural History, Royal Ontario MuseumDepartment of Ecology and Evolutionary Biology, University of Toronto
  • , Philip J. CurrieAffiliated withDepartment of Biological Sciences, CW 405 Biological Sciences, University of Alberta
  • , Mark A. LoewenAffiliated withNatural History Museum of Utah and Department of Geology and Geophysics, University of Utah

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


Chasmosaurinae Mercuriceratops gemini Campanian Judith River Formation Dinosaur Park Formation Laramidia