The word dinosaur was coined by Richard Owen in 1841, deinos (terrible) + sauros (lizard) which describe various extinct reptiles of the orders Saurischia and Ornithischia that flourished during the Mesozoic Era. Dinosaurs were carnivorous or herbivorous, dwelled mostly on land, and varied from the size of a small dog to the largest land animals that ever lived. Monoclonius ("single sprout") was a ceratopsian dinosaur. Ceratopsia or Ceratopia ("horned faces") is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. Shown here is a Monoclonius nasicornus skeleton (material now known to belong to Centrosaurus or Styracosaurus).