This tiny tooth belonged to the "tank dinosaur" of the Cretaceous.
Euoplocephalus, appropriately meaning "well-armored head" is a genus of large ankylosaur dinosaurs that lived roughly 95 - 65 million years ago in North America. Like other ankylosaurs, its body was protected by thick skin, bony armor plates and spikes, and it had a large club at the end of its tail. However, it was unique as it also had a bone that protected the eyelid.
These hard-beaked herbivores grew about 20 feet long and could weigh up to 2 tons. Similar to all ankylosaurs, Euoplocephalus had just a single curved row of teeth that were used to chew and grind plants.
Two Medicine Formation, Montana
Size: .44 x .38 x .19 inches
Weight: .01 oz