What are brachiosauras

Brachiosaur, many member or relative of the dinosaur genus Brachiosaurus, which lived 150 million to 130 million years ago from the Late Jurassic to the Early Cretaceous Period. Brachiosaurs were the heaviest and tallest sauropod dinosaurs for which complete skeletons exist; larger fossil bones belonging to other (and possibly related) sauropods have been found, but these specimens are incomplete. Fossilized remains of brachiosaurs are found in Africa, North America, and Europe. 

Brachiosaurs were built like huge giraffes; they had immensely long necks and relatively short tails. Their morphology is unusual among dinosaurs in that the forelimbs were longer than the hind limbs. These adaptations apparently enabled them to lift their heads to about 12 metres (39 feet) above the ground in order to browse the branches of tall trees. Brachiosaurs attained a maximum length approaching 25 metres and a weight of nearly 80 metric tons. Their nasal bones were expanded into a broad arch that presumably allowed them to maintain some distance between the vegetation and the nasal openings so that they could breathe easily while feeding.