Edmontonia walked on four legs and was a plant-eater. It had a pear-shaped skull (when viewed from the top). The neck and part of the back were protected by large, flat, keeled (ridged) plates. Smaller keeled plates covered the back, hips, and tail. Spines and large spikes along its sides would have made the animal look short and wide when viewed from the front. This made it look more menacing to an enemy.
An Albertosaurus was not the only animal it needed to protect itself from. A male Edmontonia probably fought with other males for territory and females. The larger males may have used their large shoulder spines for shoving contests. The spines of Edmontonia would have been dangerous to rival males or to an Albertosaurus or Daspletosaurus, if they got too close. Like other ankylosaurs, Edmontonia most likely spent most of its life alone. It was nearly completely covered in armor, with only its soft underbelly left unprotected. If a predator like Albertosaurus came by, it just tucked itself as close as it could to the ground and wait for the tyrannosaur to pass. Along with armor, Edmontonia also had long, sharp, scissor-like spikes along its shoulders, some growing to be nearly a foot and a half (46 cm.) long. It had a thick, tank-like body with stout, slow legs. It didn't have a club on the end of its tail like its more famous cousins Ankylosaurus and Euoplocephalus, but it ended in more like a sharp, bony whip, probably good for whapping tyrannosaur legs and making them back-off.
In Popular Culture
Edmontonia is featured in March of the Dinosaurs, where one lives up in the Arctic Circle along with a herd of Edmontosaurus and Pachyrhinosaurus. When the other two herds migrate South to escape the freezing winter, the Edmontonia stays behind and slips in the snow while trying to get some food, and is flipped over onto its back, unable to flip itslef back over. It was nearly killed by a pack of Troodon and a Gorgosaurus, but the tyrannosaur flips it while trying to take the ankylosaur from the Troodon, and the nodosaur mortally wounds it. It then continued on its way and continued to live on as the herds returned. An Edmontonia appears in Life After Dinosaurs where it is shown inaccurately to live in South America.