Brachyceratops = Rubeosaurus

Zástupci kladu Centrosaurinae (Ornithischia, Ceratopsia) jsou známi ze středního kampánu souvrství Two Medicine z Montany, a to ve čtyřech taxonech: Brachyceratops montanensis, Rubeosaurus ovatus, Einiosaurus procurvicornis a Achelousaurus horneri. K rubeosaurovi byl v minulosti zařazena jen přepážka temenní kosti a nekompletní lebka. Revidovaná interpretace temene jedince USNM 14765, klasifikovaného jako brachyceratops, pak ukazuje, že osten P5 je shodný s holotypem Rubeosaurus ovatus a může být tedy řazen k tomuto taxonu, přičemž brachyceratops je nomen dubium. V analýze je pak rubeosaurus sesterským taxonem kladu složeného z einiosaura, achelousaura a pachyrinosaura.

Zdroj/abstrakt:

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.

Methodology/Principal Findings
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/Significance
USNM 14765 provides additional anatomical information for Rubeosaurus ovatus. These new data are incorporated into a recent phylogenetic nalysis of centrosaurine relationships; Rubeosaurus appears as the sister axon of a clade composed of Einiosaurus, Achelousaurus, and Pachyrhinosaurus.

Citace:

McDonald AT, 2011 A Subadult Specimen of Rubeosaurus ovatus (Dinosauria: Ceratopsidae), with Observations on Other Ceratopsids from the Two Medicine Formation. PLoS ONE 6(8): e22710.