RESEARCH ARTICLE Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus magniventris Victoria M. Arbourab* and Jordan C. Mallonc aDepartment of Palaeobiology, Royal Ontario Museum, 100 Queens Park, Toronto, ON M5S 2C6, Canada; bDepartment of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, ON M5S 3B2, Canada; cPalaeobiology, Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, ON K1P 6P4, Canada *
[email protected] Abstract Ankylosaurus magniventris is an iconic dinosaur species often depicted in popular media. It is known from relatively fragmentary remains compared with its earlier and smaller relatives such as Euoplocephalus and Anodontosaurus. Nevertheless, the known fossils of Ankylosaurus indicate that it had diverged significantly in cranial and postcranial anatomy compared with other Laramidian ankylo- saurines. In particular, the dentition, narial region, tail club, and overall body size differ substantially from other Campanian–Maastrichtian ankylosaurines. We review the anatomy of this unusual ankylo- saur using data from historic and newly identified material and discuss its palaeoecological implications. Key words: Maastrichtian, Laramidia, North America, Ankylosauria, Ankylosauridae, palaeoecology OPEN ACCESS Introduction The iconic Maastrichtian dinosaur Ankylosaurus magniventris was the last and largest of the ankylo- Citation: Arbour VM and Mallon JC. 2017. saurid dinosaurs. A member of the tail-clubbed clade of armoured dinosaurs, the ankylosaurines, Unusual cranial and postcranial anatomy in the archetypal ankylosaur Ankylosaurus Ankylosaurus was part of a lineage that dispersed into North America from Asia during the Late magniventris.FACETS2:764–794. Cretaceous (Arbour and Currie 2016). Like other ankylosaurines, Ankylosaurus was a bulky, broad doi:10.1139/facets-2017-0063 quadruped studded with osteoderms of various shapes and sizes, and had a stiff distal tail with enlarged osteoderms enveloping the tail tip to form a formidable tail club.