A Subadult Specimen of Rubeosaurus ovatus (Dinosauria: Ceratopsidae), with Observations on Other Ceratopsids from the Two Medicine Formation

Andrew Allen Farke,Andrew T. McDonald

doi:10.1371/journal.pone.0022710

Andrew Allen Farke, Andrew T. McDonald

Open Access

https://doi.org/10.1371/journal.pone.0022710

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Journal: PLoS ONE	Publication Date: Aug 10, 2011
Citations: 16	License type: CC BY 4.0

Affiliation: University of Pennsylvania

Abstract

BackgroundCentrosaurine 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.Methodology/Principal FindingsA 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/SignificanceUSNM 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.

Highlights

Centrosaurine ceratopsids are among the most ornate dinosaurs, sporting all manner of spikes, hooks, and protuberances on their parietosquamosal frills
Rubeosaurus ovatus was originally named as a new species of Styracosaurus by Gilmore [12] based upon the caudal parietal bar of a large centrosaurine from the Upper Two Medicine Formation of Montana (Fig. 1) [13,14]
Even with the flurry of new centrosaurines discovered in the last two decades, this morphology remains unique to USNM 11869 and can be considered an autapomorphy of Rubeosaurus ovatus

Summary

Introduction

Centrosaurine ceratopsids are among the most ornate dinosaurs, sporting all manner of spikes, hooks, and protuberances on their parietosquamosal frills. Rubeosaurus ovatus was originally named as a new species of Styracosaurus by Gilmore [12] based upon the caudal parietal bar of a large centrosaurine from the Upper Two Medicine Formation of Montana (Fig. 1) [13,14].

Results

Conclusion