The Postcranial Anatomy of Pachycephalosaurs (Ornithischia: Pachycephalosauria) and its Phylogenetic and Myological Implications

Pachycephalosaurs are a group of small-bodied, bipedal ornithischian dinosaurs. They are best known for their characteristic fusion of the frontals and parietals into a "skull dome". This feature is the most commonly preserved element of pachycephalosaurs and therefore much research has been dedicated to their cranial anatomy. The postcranial skeleton is not often preserved and does not receive the same attention. CMN 22039 at the Canadian Museum of Nature represents a rare postcranial specimen. The goal of this study is to use CMN 22039 with other comparable specimens to investigate the postcranial anatomy of pachycephalosaurs in both a functional and phylogenetic context. Examining CMN 22039 alongside other pachycephalosaurs revealed that new postcranial characters change the current phylogeny of pachycephalosaurs, although, it remains unclear if this is due to ontogenetic variations. Studying the postcranial anatomy of Stegoceras validum also facilitated the first detailed myological reconstruction of the appendicular skeleton of pachycephalosaurs.