Euoplocephalus Characteristics

Euoplocephalus was 20 feet (6 metres) long and weighed about 2 tons. While it was 8 feet (2.4 metres) wide, it was low-slung, with short, stout legs. The rear legs were larger than the front legs and all 4 limbs were tipped with hoof-like claws. A track way of an ankylosaur, found in 1996, at Sucre, Bolivia, indicates that Euoplocephalus could probably have moved with moderate speed.

Like all ankylosaurids, it had a flat, thick, triangular skull, with little capacity for a brain. The mouth was a horny beak and the teeth were small, weak and peg-like and it had a short neck. The entire head and body of the Euoplocephalus was covered with bands of armour, which allowed a surprisingly amount of flexibility. It was the first ankylosaurid discovered with armoured shutters that it could slide down to cover its eyelids. The armour would have protected Euoplocephalus from carnivorous predators. Among its contemporaries were the large meat-eating Tyrannosaurus Rex, Tarbosaurus and Deinonychus.

Each narrow band of armour was composed of a thick oval plate, embedded in the thick surrounding skin, which was studded with short, horny spikes (dermal scutes, like those of crocodiles), which were about 10 to 15 centimetres (4 to 6 inches) long. In addition to the spines running down its back, Euoplocephalus had large horns growing from the back of its head.

Euoplocephalus also had a bony club at the end of its rigid tail, which it carried in a raised position. The tail was muscular, so the club could be swung from side to side for defence.

Internally, many bones were fused together to provide support for the heavy armour. The backbone (the dorsal vertebrae) is merged with the ribs, and several of the backbones in front of the hips (presacral vertebrae) were also fused together into a rod. The tail is made from hardened tissues, which are fused to the tail bones (known as caudal vertebrae).

The underbelly of Euoplocephalus was not as heavily armoured as its back. Like a porcupine, flipping it over may have been the only way to harm it.

Euoplocephalus was a plant eating (herbivorous) dinosaur. It had a complicated nose design (nasal structure), which indicates that it probably had a good sense of smell. It had flexible legs, which it might have used for digging. The stiff, low-slung dinosaur had poor teeth (weak dentition), so it probably would have grazed on fleshy low-lying vegetation and shallow tubers. Euoplocephalus would have had to eat a huge amount of vegetation to sustain itself. Euoplocephalus may have traveled in herds.

Fossils from more than 40 individuals have been discovered in Alberta, Canada and Montana in the United States, making Euoplocephalus the best known ankylosaurid. This includes 15 skulls, teeth, and a few almost-complete skeletons, found with the armor still attached. Individual armour plates are the most commonly found element from them.

Euoplocephalus was named by Lawrence M. Lambe in 1910.