Bakker described the skull as being much wider at the rear than "Edmontonia" specimens. In 1988, Robert Thomas Bakker decided to split the genus "Edmontonia". Flat oblong plates resembled the ones that guarded the neck of the nodosaurid "Edmontonia rugosidens". One ankylosaurian and two nodosaurians are known, "Ankylosaurus", "Denversaurus" and possibly "Edmontonia". C.M. Sternberg originally did not provide a classification of "Edmontonia". The generic name "Edmontonia" refers to Edmonton or the Edmonton Formation. Two separate studies have found "Animantarx" to be the sister taxon of "Edmontonia" within Nodosauridae. In 1940, Loris Shano Russell referred all three specimens to "Edmontonia", as an "Edmontonia rugosidens". In "Edmontonia longiceps" and "E. rugosidens" the deltopectoral crest of the humerus is gradually rounded. Struggling, the "Edmontonia" gets back up and injures the "Gorgosaurus" with her shoulder spikes. This group traditionally includes "Nodosaurus", "Edmontonia", and "Sauropelta". In 1943, American paleontologist Barnum Brown referred the find to "Edmontonia longiceps". "Edmontonia" was bulky, broad and tank-like. Edmontonia was an armoured dinosaur, part of the nodosaur family from the Late Cretaceous Period. "Edmontonia" was generally shown to be a derived nodosaurid, closely related to "Panoplosaurus".