Polacanthus sported a thick coat of bony armour plates covering its rump. It had evenly spaced rows of fierce spikes along its sides and on its shoulders. These defences were well needed in its day - giant Theropods stalked the land, and newer, sleeker killers had evolved, the infamous Dromaeosaurs. Utahraptor lived at the same time Gastonia and Polacanthus (Gastonia being the American equivalent of the European Polacanthus) Such a terrifying 'mega raptor', 6 metres long, would have needed to be kept in check. Even the most desperate Utahraptor would have preferred far easier meals such as ornithopods and young Sauropods.