inflexible and dorsoventrally, vertically, flexible. This meant that brachiosaurids could angle their necks up and lift their heads, enabling them to graze from treetops up to a height of about fourteen meters. It has been argued that other sauropods lacked this dorsoventral flexibility and that their necks stretched outwards in front of them instead of upwards. Brachiosaurids have more often been found in the conifer-rich sites, like the Tendaguru, than in the Morrison deposits, suggesting that their fitness was increased by the presence of taller conifer food sources. However, the giant size and long necks of brachiosaurids meant that they required tremendous pressure to bring oxygenated blood to their brains. It has been proposed that sauropods possessed a four-chambered double pump heart, with one pump for oxygenated and one pump for deoxygenated blood. As in all Macronaria, the forelimbs of brachiosaurids are long relative to the hindlimbs, but this trait is more pronounced in brachiosaurids. The forelimbs were very slender for a sauropod and the metacarpal bones of the forelimb were elongated. These adaptations overall increased the stride length of the forelimbs, arguably resulting in an uneven gait. However, it was previously argued that they were hindlimb dominant like other sauropods, and thus had the ability to rear up on their hindlimbs. Based on the structure of their legs, making it impossible for them to run, it is likely that they moved about in a low walking speed (20–40 km/day), but were capable of moving faster when necessary, up to 20–30 km/hour, depending on leg length. Brachiosaurids shared synapomorphies, new traits typical for the group. They possessed middle and rear back vertebrae with long, 'rod-like' transverse processes. In the pelvis, the ischium had a shortened pubic peduncle, the contact surface with the pubic bone. Their humeri, upper arm bones, had a large deltopectoral crest. Their skull roofs showed wide supratemporal fenestrae, openings for the muscles. They had neural arches placed more on front of the vertebrae, shoulder blades that were expanded at the top end, irregularly shaped coracoids in the shoulder girdle, and triangular projections on the underside of the front branch of their quadratojugal bones at the lower rear corner of the skull. History of findings Changing classifications In 1903, Elmer Samuel Riggs described and named Brachiosaurus. In 1904, he created a new sauropod family, the Brachiosauridae. He published a complete description of the phenotype after examining the humerus,