Illustration of Diplodocus dinosaurs. This herbivorous sauropod dinosaur lived from about 154 to 150 million years ago during the Late Jurassic Period, in what is now North America. It is thought to have reached a length of up to 33 metres and a weight of 23 tonnes. This is light for such a large animal. This was in part due to air spaces within the bones, but also due to air sacs (yellow) that extended from the chest into the neck. The lungs are blue.