Austria – 3 Euro, Argentinosaurus Huinculensis, 2021. The heyday of prehistoric reptiles began around 230 million years ago and they ruled the Earth for more than 160 million years. More than 1,000 different types of these extinct giants have already been found. The largest and most impressive animals to have ever lived, dinosaurs colonised all the continents and came in a huge variety of shapes and sizes.