page_title: Edmontonia
section_title: Skeleton
hierarchical_section_title: Edmontonia / Description / Skeleton
caption_attribution_description: Edmontonia armour
context_page_description: Edmontonia is a genus of armoured dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation, the unit of rock it was found in.
context_section_description: The skull of Edmontonia, up to half a metre long, is somewhat elongated with a protruding truncated snout. The snout carried a horny upper beak and the front snout bones, the premaxillae, were toothless. The cutting edge of the upper beak continued into the maxillary tooth rows, each containing fourteen to seventeen small teeth. In each dentary of the lower jaws, eighteen to twenty-one teeth were present. In the sides of the snout large depressions were present, "nasal vestibules", that each possessed two smaller openings. The top of these was a horizontal oval and represented the bony external nostril, the entrance to the nasal cavity, the normal air passage. The more rounded second opening below and obliquely in front, was the entrance to a "paranasal" tract, running along the outer side of the nasal cavity, in a somewhat lower position. A study by Matthew Vickaryous in 2006 proved for the first time the presence of multiple openings in a nodosaurid; such structures had already been well established in ankylosaurids. The air tracts are however, much simpler than in the typical ankylosaurid condition, and are not convoluted while lacking bony turbinate bones. The nasal cavity is separated into two halves along the midline by a bone wall. This septum is continued to below by the vomers, which are keeled, the keel featuring a pendulum-shaped appendage. Another similarity with Ankylosauridae is the presence of a secondary bone palate, a possible case of parallel evolution. This has been shown too for Panoplosaurus.
  The head armour tiles, or caputegulae, are smooth. Details differ between the various specimens but all share a large central nasal tile on the snout, bend large "loreal" tiles at the rear snout edges and a large central caputegula on the skull roof. The tiles behind the upper eye socket rim in Edmontonia longiceps do not stick out as much as in E. rugosidens, combined with a more narrow, pointed snout in the former. Some E. rugosidens specimens are known that possess a "cheek plate" above the lower jaw. Contrary to that discovered with Panoplosaurus, it is "free-floating", not fused with the lower jaw bone.
  The vertebral column contains about eight neck vertebrae, about twelve "free" back vertebrae, a "sacral rod" of four fused rear dorsal vertebrae, three sacral vertebrae, two caudosacrals and at least twenty, but probably about forty, tail vertebrae. In the neck the first two vertebrae, the atlas and axis, are fused. In the shoulder girdle, the coracoid has a rectangular profile, in contrast to the more rounded shape with Panoplosaurus. Two sternal plates are present, connected to sternal ribs. The forelimb is robust but relatively long. In Edmontonia longiceps and E. rugosidens the deltopectoral crest of the humerus is gradually rounded. The metacarpus is robust compared to that of Panoplosaurus. The hand very likely was tetradactyl, having four fingers. The exact number of phalanges is unknown but the formula was by W.P. Coombs suggested to be 2-3-3-4-?.
caption: The AMNH 5381 specimen of E. rugosidens, 1915 (first referred to Palaeoscincus by Matthew in 1922), showing the position of the dermal armour
exif: {}