title: A subadult specimen of Rubeosaurus ovatus (Dinosauria: Ceratopsidae), with observations on other ceratopsids from the two medicine formation.
abstract: BACKGROUND
  Centrosaurine ceratopsids are well known from the middle Campanian Upper Two Medicine Formation of Montana. Four taxa have been named: Brachyceratops montanensis, Rubeosaurus ovatus, Einiosaurus procurvicornis, and Achelousaurus horneri. Rubeosaurus has been historically the most enigmatic of these taxa; only two specimens, the holotype caudal parietal bar and a referred incomplete skull, have been assigned to Rubeosaurus.
  
  
  RESULTS
  A revised interpretation of the parietal processes of USNM 14765, the partial skeleton of a subadult centrosaurine formerly referred to Brachyceratops, indicates that it shares a P5 spike with the holotype of Rubeosaurus ovatus and should therefore be referred to that taxon. Brachyceratops is considered a nomen dubium.
  
  
  CONCLUSIONS
  USNM 14765 provides additional anatomical information for Rubeosaurus ovatus. These new data are incorporated into a recent phylogenetic analysis of centrosaurine relationships; Rubeosaurus appears as the sister taxon of a clade composed of Einiosaurus, Achelousaurus, and Pachyrhinosaurus.
authors.affiliation: Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America. mcandr@sas.upenn.edu
authors.forename: Andrew T
authors.initials: AT
authors.lastname: McDonald
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001842:Bone and Bones / Q000033:anatomy & histology; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification*; D005580:Fossils; D009009:Montana; D010802:Phylogeny; D013048:Specimen Handling