Edmontonia

Phylogeny: Dinosauria > Ornithischia > Genasauria > Thyreophora > Thyreophoroidea > Eurypoda > Ankylosauria > Euankylosauria > Nodosauridae > Panoplosaurini

Overview: Fossils of this armored herbivore were originally unearthed in the mid-1910’s, in what is now Alberta, Canada. These were at first referred to a genus called Palaeoscincus, which is usually seen as a dubious taxon today. Said fossils, however, weren’t the holotype specimen. The actual holotype was found almost a decade later, also in Alberta, later described in 1928 under the name Edmontonia longiceps. In the 1940’s, the fossils referred to Palaeoscincus were reclassified as an additional species; Edmontonia rugosidens. The generic name of Edmontonia can refer to either the Canadian city of Edmonton, located near to where the holotype was found, or to what was then known as the Edmonton Formation – now the Horseshoe Canyon Formation. Edmontonia fossils have also been reported from the Dinosaur Park and Judith River Formations, the latter extending its range across the American border, into the state of Montana. Many specimens of Edmontonia are decently preserved and consist of much of the skeleton, as well as its dermal armor. This makes it one of the best understood ankylosaurs from North America.

Edmontonia is usually classified as a member of the ankylosaur family Nodosauridae, with genera like Panoplosaurus and Denversaurus being among its closest relatives. All three are usually placed within the nodosaurid tribe Panoplosaurini. Nodosaurids tended to have narrower snouts than those seen on the ankylosaurids, which is readily observable on the skulls we have of Edmontonia itself. In most cases, ankylosaurids had tail clubs, while Edmontonia and other nodosaurids lacked them. What this dinosaur did have, however, was a large array of formidable spikes growing on its sides, neck, and especially on the shoulders. The largest spines pointed forwards, sometimes bearing smaller branching projections coming off the main spike. Edmontonia may’ve been able to ram into an attacker with these spines if it had no means of escape. Its dermal armor took on other forms across the top of its neck, back and tail, as rows of flat plates or ridged scutes. Edmontonia had use for such armor, considering it lived with a number of large tyrannosaurs, such as Gorgosaurus, Daspletosaurus or Albertosaurus, depending on the geological formation and region.