Temporal Range: Late Cretaceous (70-65 Mya)
Length: 6 metres
Height: 2 metres
Feeding Type: Herbivore
- Discovery: Lawrence Morris Lambe discovered the first specimen of Euoplocephalus in 1902 and named it Stereocephalus; however that name was already preoccupied (it had already been given to a type of insect), so Lambe renamed it, Euoplocephalus in 1910. Although Ankylosaurus is the most famous ankylosaurid dinosaur in popular culture, Euoplocephalus is probably the best known in the palaeontological industry. Researchers have recovered over forty individual Euoplocephalus specimens from Alberta, Canada and Montana, USA. The forty specimens consist of over fifteen known skulls, as well as a few almost-complete specimens with armour plating still attached.
- Statistics: Among the ankylosaurids, Euoplocephalus was exceeded in size only by Tarchia and Ankylosaurus. The wealth of fossil material recovered means researchers have been able to create fairly certain length and weight estimates; with many believing Euoplocephalus would have grown to around 6 metres in length and weighed 2,000kg.
- Description: The skull is the most extensively studied area of Euoplocephalus, and it is wider than it is long. The skull shape gives Euoplocephalus a very broad mouth structure, which suggests it was a generalist browser of low vegetation and possibly had a more advanced, or larger digestive system, to cope with ingestion of a greater variety of plant material. The teeth inside the mouth of Euoplocephalus are small, and like other ankylosaurids are more suitable for chopping.
Euoplocephalus also has a complex series of nasal passages that are in the snout (an adaptation seen in other ankylosaurid dinosaurs, such as Saichania). Initial explanations for these nasal passages were that they would allow a greater sampling of air, giving Euoplocephalus an increased sense of smell. However, endocasts of the brain suggest this was not the case; instead it seems that the purpose of these passages was to moisten inhaled air. Euoplocephalus itself appears to have been present in ecosystem with dry climates, and having the ability to moisten inhaled dry air would have made these types of climates far more tolerable for Euoplocephalus to live in. In addition, this adaptation would relieve them of respiratory problems as well as reducing the amount of moisture lost during respiration.
The back and upper flanks of Euoplocephalus were covered in bony armour plates (known as osteoderms). The main osteoderms were arranged in bands that followed one another down the length of the animal; forming armour that was rigid but flexible, so the normal movement of Euoplocephalus was not hindered. In addition to the plates, large spikes rose up vertically from the body; particularly two large spikes rose up from above the shoulders. These spikes would have made it more difficult for large predators to gain a grip on the body with their mouths, reducing the chance of effectively biting through the armour plates. In addition, like with other ankylosaurids, the lower portion of the tail of Euoplocephalus was rigid due to ossified tendons, meaning the tail was only flexible in the upper portion. Combined with the bony club on the end, this would allow Euoplocephalus to swing its tail at other dinosaurs; possibly as a self-defence mechanism for use against predators, or as a weapon used in intra-species combat.