Euoplocephalus tutus

One of the better represented ankylosaurs, Euoplocephalus lived during the Late Cretaceous, around 75 million years ago in Alberta, Canada. A well-armored dinosaur, it also had a tail club which may have helped in defense against predators, but also seems to have been used in intraspecific competitions, where individuals would have squared off and swung their clubs at one another, presumably producing terrifying “thwacks” as rivals pounded each other’s armor.

Although older descriptions often depict armored dinosaurs as simply hunkering down and ignoring predators, the larger, bone-crushing tyrannosaurs like Daspletosaurus would probably have been too dangerous to ignore like this, and one can imagine them trying to keep the most heavily armored parts of themselves facing the predator, or retreating and waving their tail-clubs to make an attack a riskier proposition.