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Euoplocephalus tutus (Lambe, 1910)

Name Means: "Well-Armored Head" Length: 20 ft. (6.5 m)
Pronounced: YOU-Opp-low-Seff-uh-luss Weight: 2 tons
When it lived: Late Cretaceous - 76 MYA Family: Ankylosauridae
Where found: Alberta, Canada; Montana, USA    
  Ankylosaurs (the clade Ankylosauria) were a group of heavily armored plant-eating dinosaurs,  which are divided into two groups.  (1) The Nodosaurids had spikes running along the sides of their bodies, pear-shaped heads, a toothless horny beak, leaf-shaped teeth in the cheeks, and lacked a clubbed-tail. (2) The Ankylosaurids which had a wide skull, massive legs and a tail club, . They lived during the Cretaceous period. and  included Ankylosaurus, Amtosaurus, Saichania, Sauroplites, Tarchia and Euoplocephalus.
   Euoplocephalus was one of the largest of the ankylosaurian dinosaurs. It was about the size of a small elephant.  Within the Ankylosaurids, only the Ankylosaurus and Tarchia were larger  Euoplocephalus had a flat, thick, triangular skull, small brain and a short neck. It had a horny beak with small, weak, peg-like teeth.  It's body was low and fat and its tail ended in a heavy, bony club, which it carried in a raised position. The tail was muscular, so the club could be swung from side to side for defense.  it weighted close to 50 pounds and was at the end of a seven-foot tail, which would have permitted it be swung with great force.  . but its long tail and heavy club would have made a formidable defensive weapon. The club weighed close to 50 pounds (20 kilos) and was on the end of a tail that was nearly 7 feet (2 m) long.  It could have easily crushed the bones of a large predator.
   Although Euoplocephalus was not as heavily armored as some of its family members. It's entire head and body was covered with bands of armor, which allowed a surprisingly amount of flexibility. It was the first ankylosaurid discovered with armored shutters that it could slide down to cover its eyelids.  Each narrow band of armor 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 centimeters (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.
      Only the underbelly of the Euoplocephalus was unarmored. Like a porcupine, flipping it over may have been the only way to harm it. A survey of dinosaur bones in Alberta, Canada supports this, showing many bite marks on dinosaurs like the unarmored Hadrosaurus, but none on the ankylosaurids. There is some speculation, however, that the incredible biting power of the Tyrannosaurus may have ultimately led to the species' extinction. This may have been risky because a swing of the tail could cause massive damage if it hit a predator in the stomach, or knocked its legs out.
    Internally, many bones were fused together to provide support for the heavy armor. The backbone (the dorsal vertebrae) is merged with the ribs, and several of the back bones 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).
    Euoplocephalus was plant eating (herbivorous) dinosaur. It had a complicated nose design (nasal structure), which indicates that it probably had a good sense of smell, and flexible legs which it might have used for digging. The stiff, low-slung dinosaur had poor teeth (weak dentition), so it must have grazed on fleshy low-lying vegetation, and shallow tubers.
    Euoplocephalus is the best known of all the Ankylosaurs. It was discovered by Paleontologist Lawrence Morris Lambe in 1902.  He first proposed the name Stereocephalus, but it had already been given to an insect, so he changed it to Euoplocephalus in 1910. This new name has been misspelled more than a dozen different ways in formal scientific literature. It was also once thought to be the same genera as Ankylosaurus.  The original species is now known as Euoplocephalus tutus, and a second species, Euoplocephalus acutosquameus (originally named Dyoplosaurus), was discovered by William Arthur Parks in 1924. While the two species have clubs with different shapes, they may actually be the same species. Specimens now assigned to the Tarchia and Ankylosaurus genera were also considered to be species of Euoplocephalus at one point.
    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 fossil remains include 15 skulls, teeth, and one almost-complete skeleton, found with the armor still attached. The tail club is particularly common.
    All the skeletons discovered have been isolated, so the conventional wisdom is that all ankylosaurids were solitary. However the discovery of a herd of 22 young Pinacosaurus was announced in 1988, which indicates that Euoplocephalus may have displayed herd behavior, at least as a juvenile. 


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