The Brachiosauridae ("arm lizards", from Greek brachion (βραχίων) = "arm" and sauros = "lizard") are a family or clade of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the leaves of tall trees that other sauropods would have been unable to reach. In addition, they possessed thick spoon-shaped teeth which helped them to consume tough plants more efficiently than other sauropods. They have also been characterized by a few unique traits or synapomorphies; dorsal vertebrae with 'rod-like' transverse processes and an ischium with an abbreviated pubic peduncle. Brachiosaurus is one of the best-known members of the Brachiosauridae, and was once thought to be the largest land animal to ever live. Brachiosaurids thrived in the regions which are now North and South America, Africa, Europe, and Asia. They first appear in the fossil record in the Late Jurassic Period (possibly even earlier in the Middle Jurassic) and disappear in the late Early Cretaceous Period. The broad distribution of Brachiosauridae in both northern and southern continents suggests that the group originated prior to the breakup of Pangaea. In the Early Cretaceous the distribution of the group is dramatically reduced. It is still unclear whether this reduction is due to local extinctions or to the limited nature of the Early Cretaceous fossil record. Brachiosauridae has been defined as all titanosauriforms that are more closely related to Brachiosaurus than to Saltasaurus. It is one of the three main groups of the clade Titanosauriformes, which also includes the Euhelopodidae and the Titanosauria. Description The Brachiosauridae are composed of quadrupedal dinosaurs that are generally very large, with the exception of the possible insular dwarf Europasaurus. The brachiosaurids can be distinguished from other macronarian taxa by their broad, thick and spoon-shaped teeth. Their maxillary teeth were twisted apically, at the top, and the shape of these teeth was optimal for biting off resistant vegetation. While brachiosaurids, like other sauropods, did not perform significant food processing in their mouths, their teeth enabled them to slice through food instead of having to pull it from tree branches. Evidence for this precision shearing consists of apical wear facets on the teeth and distinctive bone structure that suggests orthal, vertical, jaw action. In addition, the characteristic long necks of brachiosaurids are distinct from those of other long-necked dinosaur taxa. They possessed a narrow neck composed of twelve to thirteen extremely long cervical vertebrae that was laterally