Brachiosaurus (meaning ""Arm lizard"") was a herbivorous dinosaur genus that lived in the Upper Jurassic period. The name comes from the fact that the Brachiosaur's front legs were longer than its back legs. Most other dinosaurs had back legs that were longer than their front legs or arms. "Brachiosaurus" was about 25 m (82 feet) long and 13 meters (42 feet) tall. It was one of the biggest dinosaurs.