Dacentrurus, meaning “very sharp tail”, is a genus of stegosaur dinosaur from the Late Jurassic Period (154 to 150 million years ago). It was described by Richard Owen in 1875 as Omosaurus armatus. It was the first stegosaur to be discovered. Its genus name was changed to Dacentrurus, as the former was already taken. Other species include D. durobrivensis, D. phillipsi, and D. vetustus. Its remains have been found in Wiltshire, Dorset, and Weymouth, England. Specimens have also been recovered in France, Spain, and Portugal.
Dacentrurus measured 20 to 33 feet in length at adulthood. It had pairs of triangular plates that ran down the spine, with four pairs of spikes on the end of the tail. For reasons unknown, many books claim that Dacentrurus was a small stegosaur. The pelvis, measuring nearly 5 feet, indicates that this dinosaur was one of the larger stegosaurs.