Dinosaur Time!

For many decades, Brachiosaurus was the largest dinosaur known. It has since been discovered that a number of giant titanosaurians (Argentinosaurus, for example) surpassed Brachiosaurus in terms of sheer mass. More recently, another brachiosaurid, Sauroposeidon, has also been discovered; based on incomplete fossil evidence, it too is likely to have outweighed Brachiosaurus.
Brachiosaurus is often considered to be the largest dinosaur known from a relatively complete fossilized skeleton. However, the most complete specimens, including the Brachiosaurus in the Humboldt Museum of Berlin (excavated in Africa, the tallest mounted skeleton in the world), are members of the species B. brancai which some scientists consider to be part of a separate genus, Giraffatitan. The holotype material of the type species, B. altithorax. includes a sequence of seven posterior dorsal vertebrae, sacrum, proximal caudal vertebra, coracoid, humerus, femur and ribs: enough from which to estimate size. Based on a complete composite skeleton, Brachiosaurus attained 25 metres (82 feet) in length and was probably able to raise its head about 13 metres (42 ft) above ground level. Fragmentary material from larger specimens indicates that it could grow 15% longer than this. Such material includes an isolated fibula HMN XV2 1340 cm in length and the brachiosaurid scapulocoracoid referred to Ultrasauros.