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.
Physiology of dinosaurs
But a preliminary study of the relationship between adult size, growth rate, and body temperature concluded that larger dinosaurs had higher body temperatures than smaller ones had; "Apatosaurus", the largest dinosaur in the sample, was estimated to have a body temperature exceeding , whereas smaller dinosaurs were estimated to have body temperatures around  – for comparison, normal human body temperature is about . Based on these estimations, the study concluded that large dinosaurs were inertial homeotherms (their temperatures were stabilized by their sheer bulk) and that dinosaurs were ectothermic (in colloquial terms, "cold-blooded", because they did not generate as much heat as mammals when not moving or digesting food). These results are consistent with the relationship between dinosaurs' sizes and growth rates (described above). Studies of the sauropodomorph "Massospondylus" and early theropod "Syntarsus" ("Megapnosaurus") reveal growth rates of 3 kg/year and 17 kg/year, respectively, much slower than those estimated of Maiasaura and observed in modern birds.