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
The Leptocleididae radiated during the Early Cretaceous. These were rather small forms that, despite their short necks, might have been more closely related to the Plesiosauridae than to the Pliosauridae. Later in the Early Cretaceous, the Elasmosauridae appeared; these were among the longest plesiosaurs, reaching up to fifteen metres (fifty feet) in length due to very long necks containing as many as 76 vertebrae, more than any other known vertebrate. Pliosauridae were still present as is shown by large predators, such as "Kronosaurus".