Euoplocephalus

Phylogeny: Dinosauria > Ornithischia > Genasauria > Thyreophora > Thyreophoroidea > Eurypoda > Ankylosauria > Euankylosauria > Ankylosauridae > Ankylosaurinae

Overview: Excluding the geologically younger Ankylosaurus, Euoplocephalus is probably the next most famous member of the family Ankylosauridae. Its overall appearance was very similar to its later relative, though Ankylosaurus may’ve been a bit larger overall. Euoplocephalus was no slouch when it came to size, however. Most size estimates put it at five to six meters in length, with a weight of two or three standard tons. Its torso was slung low to the ground, supported by four strong legs, with dermal armor covering most of the top surface of its body. This included its back, sides, neck, tail, and head. Even its eyelids were protected by a thin layer of bone. As with other ankylosaurids, Euoplocephalus also sported a club of bone on the end of its tail, probably used as a more active defense and for side-to-side strikes against competition of its own species (at least in the context of males). The bony scutes that made up its armor varied in size. Some were small, forming a kind of pavement-like surface, while others were much larger, ridged and even pointed, especially over the shoulders. Similar to its close relatives, it had horn-like osteoderms on the back of its skull.

Euoplocephalus was first discovered in Alberta, Canada by the renowned Canadian paleontologist Lawrence M. Lambe, in the late 1890’s. This first set of fossils was fairly fragmentary, but enough was present to confirm it was a genus unknown to science. Lambe first described the remains in 1902, initially naming it Stereocephalus, meaning “solid head”. However, this name turned out to already be in use for a genus of beetle. Lambe officially renamed it in 1910, under its current name. Euoplocephalus literally means “well-armored head”, which like its original name, was inspired by the impressive armor over its skull. More complete fossils would be found later, with over a dozen specimens being known today. There used to be more specimens, however. From the 1970’s to the 2010’s, other ankylosaurids in the region like Scolosaurus, Anodontosaurus and Dyoplosaurus were treated as junior synonyms, but they are now generally seen as related, but distinct taxa. Definitive fossils are known from the famous Dinosaur Park Formation, so it coexisted with Parasaurolophus, Lambeosaurus, Centrosaurus, Chasmosaurus, Edmontonia, Gorgosaurus, and Daspletosaurus.