North American Dinosaurs

Edmontonia

Size
Edmontonia was bulky, broad and tank-like. Its length has been estimated at about 6.6 m (22 ft). In 2010, Gregory S. Paul considered both main Edmontonia species, E. longiceps and E. rugosidens, to be equally long at six metres and weigh three tonnes.

Edmontonia had small, oval ridged bony plates on its back and head and many sharp spikes along its sides. The four largest spikes jutted out from the shoulders on each side, the second of which was split into subspines in E. rugosidens specimens. Its skull had a pear-like shape when viewed from above. Its neck and shoulders were protected by three halfrings made of large keeled plates.

Discovery and species
In 1915, the American Museum of Natural History obtained the nearly complete, articulated front half of an armoured dinosaur, found the same year by Barnum Brown in Alberta, Canada. In 1922, William Diller Matthew referred this specimen, AMNH 5381, to Palaeoscincus in a popular-science article, not indicating any particular species. It had been intended to name a new Palaeoscincus species in cooperation with Brown but their article was never published. Matthew also referred specimen AMNH 5665, the front of a skeleton found by Levi Sternberg in 1917. In 1930 Charles Whitney Gilmore referred both specimens to Palaeoscincus rugosidens.

Facts about Edmontonia
The large spikes were probably used between males in contests of strength to defend territory or gain mates. The spikes would also have been useful for intimidating predators or rival males, passive protection, or for active self-defense. The large forward pointing shoulder spikes could have been used to run through attacking theropods.

Habitat
Edmontonia was a herbivore. It lived in the Late Cretaceous period and inhabited North America. Its fossils have been found in places such as Coahuila (Mexico), Montana and South Dakota.