Brontosaurus
"Brontosaurus" was a large, long-necked quadrupedal animal with a long, whip-like tail, and forelimbs that were slightly shorter than its hindlimbs. The largest species, "B. excelsus", weighed up to and measured up to long from head to tail. For comparison, the current largest land animal, the average male African bush elephant is 3.20 m (10.5 ft) tall at the shoulder and has a body mass of 6,000 kg (13,228 lb) or 6.6 short tons.
Brontosaurus
"Brontosaurus" may have been a more solitary animal than other Morrison Formation dinosaurs. As a genus, "Brontosaurus" existed for a long span of time, and have been found in most levels of the Morrison. "B. excelsus" fossils have been reported from the upper Salt Wash Member to the upper Brushy Basin Member, ranging from the middle to late Kimmeridgian age, about 154–151 Mya. Additional remains are known from even younger rocks, but they have not been identified as any particular species. Older "Brontosaurus" remains have also been identified from the middle Kimmeridgian, and are assigned to "B. parvus". Fossils of these animals have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma, and Utah, present in stratigraphic zones 2–6.