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.
Nipponosaurus
The immature holotype specimen measures roughly four meters (13 feet) in length. When it was originally described, it was considered to be an adult, because of its co-ossified sacral vertebra. Future authors doubted this, merely citing its small size. In the 2004 redescription, it was examined more closely and several characteristics were found that identified it as an juvenile individual. Later, in 2017, another team re-evaluated the specimen, and determined through investigating the fossils at a microscopic level (in a process called histology) that this was correct, although they doubted the significance of some of the characters identified in the former study.