Stegosaurus is one of the most recognisable dinosaurs, for one main reason: the big, triangle-shaped plates lining its neck, back and tail. They are arranged in two rows of alternating pairs, and at the tip of the tail they transition into a line of foreboding spikes, each more than 30cm long. The largest plates, located over the back and hips, are the size of coffee tables. Seen in side view, Stegosaurus cuts a unique profile. But it is hardly alone – such plates are a defining feature of a wider group called the stegosaurs, comprised of Stegosaurus and its closest fossil relatives like Kentrosaurus and Huayangosaurus.