Apatosaurus "Apatosaurus" may have been more solitary than other Morrison Formation dinosaurs. Fossils of the genus have only been found in the upper levels of the formation. Those of "Apatosaurus ajax" are known exclusively from the upper Brushy Basin Member, about 152–151 mya. "A.louisae" fossils are rare, known only from one site in the upper Brushy Basin Member; they date to the late Kimmeridgian stage, about 151mya. Additional "Apatosaurus" remains are known from similarly aged or slightly younger rocks, but they have not been identified as any particular species, and thus may instead belong to "Brontosaurus". The Morrison Formation records a
Barosaurus might have favoured those with longer necks. (See video "Neck Impossible" at reference.) Books: Barosaurus Barosaurus ( ) 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 Africa, as exemplified by the Kadsi Formation). It is present in stratigraphic zones 2-5. The composite term "Barosaurus" comes from the Greek words "barys" (βαρυς) meaning "heavy" and "sauros" (σαυρος) meaning "lizard"; thus "heavy lizard". "Barosaurus" was an enormous animal, with some adults measuring more than 26 meters