When the platypus was first introduced to the Europeans in the 1700's nobody believed it existed because of how strange it was. However platypuses actually date back to prehistoric times, and these dinosaur platypuses grew up to 1 metre in length, and fossils have been found of these giant platypuses not only in Australia, but a tooth was also found in Argentina. The oldest species that is related to the platypus is the Steropodon galmani and it is 110 million years old and represents one of Australia's oldest mammals(yes, mammal). But platypuses have evolved and changed heaps since the dinosaurs. one of the most notable changes is that the platypus got reduced from a whole metre to half of that. Also, the platypus lost its teeth, which were instead replaced with pads that specialize in chewing and crunching up their food.