Edmontonia

Edmontonia rugosidens was a formidable nodosaurid ankylosaur that roamed the coastal plains and river valleys of western North America during the Late Cretaceous, approximately 76 to 73 million years ago. This heavily built herbivore reached lengths of nearly 7 meters and weighed around 3 tonnes, making it one of the largest nodosaurids known to science.

The animal's body plan was quintessentially defensive. Its back and flanks were covered in a mosaic of bony osteoderms embedded in the skin, ranging from small rounded nodules to larger keeled plates. Most dramatically, Edmontonia bore massive forward-projecting shoulder spines—the largest of which could exceed 50 centimeters in length. These formidable weapons likely served both as deterrents to predators like Gorgosaurus and potentially in intraspecific combat between rivals.

Unlike its ankylosaurid cousins, Edmontonia lacked a tail club, instead relying entirely on its passive armor and shoulder weaponry for defense. Its skull was relatively narrow with a beak suited for selective low browsing on ferns, cycads, and other ground-level vegetation. The species name 'rugosidens' refers to its distinctive wrinkled or ridged teeth, adapted for processing tough plant material.

Fossils of Edmontonia have been recovered from multiple formations across Alberta and Montana, providing excellent understanding of nodosaurid anatomy and contributing significantly to our knowledge of Cretaceous armored dinosaur diversity.