Barosaurus (/ˌbæroʊˈsɔːrəs/ BARR-o-SAWR-əs) was a giant, long-tailed, long-necked, plant-eating dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Dakota (and possibly the Tendaguru Formation of Tanzania). It is present in stratigraphic zones 2-5.