Illustration of Brachiosaurus dinosaurs wading in water. Brachiosaurus was the tallest dinosaur, standing up to 16 meters tall. Its front legs were longer than its hind legs and it is thought that it fed on the high leaves of trees, as giraffes do today. It lived in the late Jurassic period, between 155 and 145 million years ago, and is thought to have lived in herds. Fossils of Brachiosaurus have been found in North America and Africa.