APATOSAURUS

formerly Brontosaurus, genus of giant herbivorous dinosaurs, one of the largest land animals of all time, found in Late Jurassic deposits of North America and Europe (163 to 144 million years ago). Apatosaurus weighed as much as 30 tons and was as much as 21 m (70 feet) long, including its long neck and tail. It had four massive and pillarlike legs. The size, shape, and features of the Apatosaurus head were disputed for more than a century after its remains were first uncovered, certainty clouded in part by incomplete fossil finds and by a suspected mix-up of fossils during shipment from an excavation site. The head was represented in models as a massive, snub-nosed skull with spoonlike teeth until 1978, when scientists rejected that representation in favour of a slender, elongated skull containing long, peglike teeth. Much discussion has centred on whether Apatosaurus and related forms were able to support their great bulk on the land or whether they were forced to adopt aquatic habits. It now seems likely that Apatosaurus was primarily a land animal. It had no skeletal features indicative of an aquatic environment, and experiments suggest that its bones could easily have supported its great weight. Even the massive Brachiosaurus, which weighed about 80 tons, was probably more often on land than in the water.