might have been in the direct line of ascent to Achelousaurus. In 2005, an analysis by Michael Ryan and Anthony Russell found Styracosaurus more closely related to Achelousaurus than to Centrosaurus. This was confirmed by analyses by Ryan in 2007, Nicholas Longrich in 2010, and Xu et al. in 2010. The same year Horner and Andrew T. McDonald moved Styracosaurus ovatus to its own genus, Rubeosaurus, finding it a sister species of Einiosaurus, while Styracosaurus albertensis was again located on the Centrosaurus branch. They also assigned specimen MOR 492, the basis of "Taxon A", to Rubeosaurus. In 2011, a subsequent study by Andrew T. McDonald in this respect replicated the outcome of his previous one, as did a publication by Andre Farke et al. In 2017, J.P. Wilson and Ryan further complicated the issue, concluding that MOR 492 ("Taxon A") was not referable to Rubeosaurus and announcing that yet another genus would be named for it. Wilson and colleagues moved MOR 492 to the new genus Stellasaurus in 2020, which therefore corresponds to "Taxon A". Their study found Rubeosaurus ovatus to be the sister species of Styracosaurus albertensis, and concluded Rubeosaurus to be synonymous with Styracosaurus. Before Achelousaurus was described, Pachyrhinosaurus canadensis had been considered a solitary aberrant form among centrosaurines, set apart from them by its unusual bosses. Achelousaurus gave evolutionary context to the Canadian species, while expanding the temporal and geographical range for what came to be seen as "pachyrhinosaurs." In all analyses, Achelousaurus and Pachyrhinosaurus were sister groups. In 2008, another closely related species was named, Pachyrhinosaurus lakustai. In that study, the term "Pachyrhinosaurs" was used for the clade consisting of Achelousaurus and Pachyrhinosaurus. When Pachyrhinosaurus perotorum was described in 2012, the clade name Pachyrostra was coined, uniting the two genera; Achelousaurus is the basalmost pachyrostran. Shared derived traits (or synapomorphies) of the group are an enlarged nasal ornamentation and a change of the nasal and brow horns into bosses. At the end of the Campanian, there seems to have been a trend of pachyrostrans replacing other centrosaurines. Also in 2012, the clade Pachyrhinosaurini was named, consisting of species more closely related to Pachyrhinosaurus or Achelousaurus than to Centrosaurus. Apart from Einiosaurus and Rubeosaurus, this included Sinoceratops and Xenoceratops, according to a 2013 study. Cladistic analyses develop gradually, reflecting new discoveries and insights. Their results can be shown in a cladogram, with the relationships found ordered in