Postcranial Anatomy of Edmontosaurus regalis (Hadrosauridae) from the Horseshoe Canyon Formation, Alberta, Canada

Abstract

Edmontosaurus regalis is common in the latest Campanian deposits of Alberta, Canada, and is known from numerous articulated cranial specimens and isolated bonebed material. Despite its large sample size and long research history, only the cranial skeleton has been described in detail with little reference to postcrania, the majority of which remained unprepared at the time of its original description. This study presents the first full description of the postcrania of E. regalis based on CMN 2289, the paratype of the species. In addition, this study presents the most completely figured postcranial skeleton of a hadrosaurid to date. CMN 2289 preserves an almost complete dorsal vertebral column, along with a complete pelvis and almost complete set of limbs, which allows for comparisons with other hadrosaurids. Quantitative analyses of dorsal vertebral morphology reveal important variations within a single individual, with implications for phylogenetic character construction. There is an overall increase in the centrum height and width along the dorsal series, compared to an overall decrease in centrum length. A high amount of variation is noted in spine height along the dorsal series. Limb proportions in CMN 2289 between the distal and proximal limb segments, as well as between the forelimb and hindlimb, are similar to other hadrosaurids and suggest little ontogenetic variation. A revised body mass estimate of E. regalis is presented at 7963 kg, twice that proposed by previous studies and similar in size to its sister taxon, E. annectens.