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.
Allosaurus
"Allosaurus" was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs. "Allosaurus fragilis", the best-known species, had an average length of , with the largest definitive "Allosaurus" specimen (AMNH 680) estimated at long, and an estimated weight of . In his 1976 monograph on "Allosaurus", James H. Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of . As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between , , and for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that is reasonable for large adults of "A. fragilis", but that is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed "Big Al", researchers using computer modelling arrived at a best estimate of for the individual, but by varying parameters they found a range from approximately to approximately .