The mastodons like Stegomastodon were animals closely related to the elephants. Many times they are confused with the mammoths – which never lived in South America – but they are different species. In order to tell them apart, all one has to do is look at their tusks. If they are curved up – and even cross in front of each other – then it is a mammoth. If they are more straight, then it is a mastodon. They weighed around five tons and their name means “Breast tooth”.