This herbivore armed with pencil-like teeth spent most of its time grazing and swallowing its food without chewing. Despite its small head and even smaller brain, this was one of the largest land animals ever existing. With a length of 25 metres and hip height of more than three metres, this dinosaur weighed almost forty tonnes. Its tail alone could reach a length of 17 metres! In terms of age, it wasn't rare for an Apatosaurus to live to be a hundred.