Cetiosauriscus was a sauropod dinosaur that lived between 166 and 164 million years ago, during the Middle Jurassic. It was a herbivore with a moderately long tail and long forelimbs, compared to other sauropods. It has been estimated at about 15 metres (49 ft) long and between 4 and 10 tonnes (3.9 and 9.8 long tons; 4.4 and 11.0 short tons) in weight. Its only known fossil includes a hindlimb and most of the rear half of a skeleton. Found in Cambridgeshire, England, in the 1890s, it was described by Arthur Smith Woodward in 1905 as a new specimen of the species Cetiosaurus leedsi, which was moved to the new genus Cetiosauriscus in 1927 by Friedrich von Huene. In 1980, Alan Charig proposed the current name Cetiosauriscus stewarti. The fossil was found in the marine deposits of the Oxford Clay Formation alongside many invertebrate groups, marine ichthyosaurs, plesiosaurs and crocodylians, a single pterosaur, and various dinosaurs, including an ankylosaur, stegosaurs, and an ornithopod.