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.
Plesiosauria
In general, plesiosaurians varied in adult length from between to about . The group thus contained some of the largest marine apex predators in the fossil record, roughly equalling the longest ichthyosaurs, mosasaurids, sharks and toothed whales in size. Some plesiosaurian remains, such as a long set of highly reconstructed and fragmentary lower jaws preserved in the Oxford University Museum and referable to "Pliosaurus rossicus" (previously referred to "Stretosaurus" and "Liopleurodon"), indicated a length of . However, it was recently argued that its size cannot be currently determined due to their being poorly reconstructed and a length of thirteen metres is more likely. MCZ 1285, a specimen currently referable to "Kronosaurus queenslandicus", from the Early Cretaceous of Australia, was estimated to have a skull length of .