Cetiosaurus (SEET-ee-oh-sawr-us) meaning 'whale lizard', from the Greek keteios/κήτειος meaning 'sea monster' (later, 'whale') and sauros/σαυρος meaning 'lizard', was a sauropod dinosaur from the Middle Jurassic Period (181-169 million years ago) in what are now Europe and Africa. It is estimated to have been about 53 feet (16 m) long and to have weighed roughly 24.8 tonnes (27.3 short tons). It was so named because its discoverer, Sir Richard Owen supposed it was a marine creature, initially an extremely large crocodile. It was a primitive, quadrupedal, long-necked, small-headed herbivore, with a shorter tail than most sauropods. It was one of the very first sauropods to be discovered and described.
Cetiosaurus or the neotype species C. oxoniensis is known from complete fossils and is relatively well known dinosaur. Cetiosaurus was like any other sauropod, with a long-neck, quadrapedal stance and a long well-balanced tail. Cetiosaurus' moderately long-neck and well proportioned to the size of its bod, it measured about 16 m (52ft) long and roughly weighed about 11 tonnes (12 short tons); the tail of Cetiosaurus was considerably longer than most medium-sized Sauropods having at least fourty-six caudal (tail) vertebrae, Cetiosaurus was heavily built for a sauropod the dorsal vertebrae (back bone) itself had a bulky build given the dinosaur somewhat of prominent ridge or hump. Unlike other later sauropods, like Apatosaurus or Brachiosaurus, the Cetiosaurus dorsal vertebrae were limited with hollow chambers; forearms were even longer than the upper arm (humerus) unlike most sauropods; this resulted in the forelimb being equally lengthed as the hindlimb.
In The Land Before Time
Several Cetiosaurus appear as background characters in The Land Before Time X: The Great Longneck Migration. They are part of the massive group of Longnecks that journey to the crater to "prevent the Bright Circle from falling out of the sky." Eventually, they all leave the crater and return to where they came from.