Named for "the flattened form and lateral cavities characteristic of the sacral vertebrae. The type species, B.suffosus, was founded on four caudal dorsal and three uncoossified sacral centra of a juvenile sauropod from the Upper Jurassic of England. The dorsal centra are gently opisthocoelous, but the cranial end is almost flat, lacking the greater convexity of Brachiosaurus.