Acrotholus NT
Name Acrotholus
Class Chordata,‭ ‬Reptilia,‭ ‬Dinosauria,‭ ‬Ornithischia,‭ ‬Pachycephalosauridae
Name Translation High Dome
Period Santonian (Cretaceous)
Location Canada
Diet Herbivore
Size 1.8 meters long
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Acrotholus (Greek for "high dome"); »pronounced ACK-roe-THO-luss« lived in Woodlands of North America <p class="MsoNormal"> They lived about 85 million years ago and ate plants. <p class="MsoNormal"> <p class="MsoNormal">Sometime during the middle Cretaceous period, about 100 million years ago, a population of ornithopods--small, bipedal, plant-eating dinosaurs—evolved into the first pachycephalosaurs. The recently announced Acrotholus is the earliest bone-headed dinosaur to be discovered in North America, predating the previous record-holder by five million years, and it's one of the earliest pachycephalosaurs yet identified—possibly only recently evolved from its ornithopod ancestors. <p class="MsoNormal">

Aside from its place at the base of the pachycephalosaur family tree, Acrotholus is also important because it points to a previously unappreciated diversity among small, herbivorous, Cretaceous dinosaurs. Even at this early date, bone-headed dinosaurs seem to have been widely diverse, albeit sharing one important characteristic: their unusually thick and rounded skulls, which presumably permitted males to butt heads at high speed for the right to mate with females. <p class="MsoNormal">