Stegosaurus

Stegosaurus stenops, about 9 m long and up to 5 tonnes, carried a double row of broad bony plates along its back, a tail with four long spikes, and a small head with a toothless beak at the front of its jaw. Othniel Charles Marsh named the genus in 1877 from fossils found near Morrison, Colorado. Its spiked tail is called a thagomizer, a term popularized by Gary Larson's Far Side cartoon in 1982.

Stegosaurus walked on short front legs and long hind legs, which put its head low to feed on ferns and cycads. The plates were probably used mainly for display, to recognize others of its species, and might have helped regulate temperature, although this is still debated. A puncture wound in an Allosaurus tail vertebra matches a Stegosaurus spike, which suggests that the tail spikes were real weapons. Stegosaurs lived in North America, Europe, Asia and Africa, and by the Cretaceous the group had faded.