Euoplocephalus

• Name: Euoplocephalus (Greek for "well-armored head"); pronounced YOU-oh-plo-SEFF-ah-luss
• Habitat: Woodlands of North America
• Historical Period: Late Cretaceous (75-65 million years ago)
• Size and Weight: About 20 feet long and two tons
• Diet: Plants
• Distinguishing Characteristics: Large spines on back; quadrupedal posture; clubbed tail; armored eyelids

About Euoplocephalus

Probably the most evolved, or "derived," of all the ankylosaurs, or armored dinosaurs, Euoplocephalus was the Cretaceous equivalent of the Batmobile: this dinosaur's back, head, and sides were completely armored, even its eyelids, and it wielded a prominent club on the end of its tail. One can imagine that the apex predators of late Cretaceous North America (such as Tyrannosaurus Rex) went after easier prey since the only way to kill and eat a full-grown Euoplocephalus would be to somehow flip it onto its back and dig into its soft belly--a process that might entail a few cuts and bruises, not to mention the occasional loss of limb.

Although its close cousin Ankylosaurus gets all the press, Euoplocephalus is the best-known ankylosaur among paleontologists, thanks to the discovery of over 40 more-or-less complete fossil specimens (including about 15 intact skulls) in the American West. However, since the remains of multiple Euoplocephalus males, females, and juveniles have never been found heaped together, it's likely that this plant-eater led a solitary lifestyle (though some experts hold out hope that Euoplocephalus roamed the North American plains in small herds, which would have afforded them an extra layer of protection against hungry tyrannosaurs and raptors).

As well-attested as it is, there's still a lot about Euoplocephalus that we don't understand. For example, there's some debate about how usefully this dinosaur could wield its tail club in combat, and whether this was a defensive or offensive adaptation (one can imagine male Euoplocephalus bonking each other with their tail clubs during mating season, rather than trying to use them to intimidate a hungry Gorgosaurus). There are also some tantalizing hints that Euoplocephalus may not have been as slow and plodding a creature as its anatomy would indicate; perhaps it was able to charge at full speed when enraged, like an angry hippopotamus!

Like many dinosaurs of North America, the "type specimen" of Euoplocephalus was discovered in Canada rather than the U.S., by the famous Canadian paleontologist Lawrence Lambe in 1897. (Lambe originally named his discovery Stereocephalus, Greek for "solid head," but since this name turned out to be already preoccupied by another animal genus, he coined Euoplocephalus, "well-armored head," in 1910.) Lambe also assigned Euoplocephalus to the stegosaur family, which was not quite as big a blunder as it may seem, since stegosaurs and ankylosaurs are both classified as "thyreophoran" dinosaurs and not as much was known about these armored plant-eaters 100 years ago as it is today.