Fauna of Australia species are nocturnal and many arboreal. Two of the five living species of monotreme occur in Australia: the platypus and the short-beaked echidna. The monotremes differ from other mammals in their methods of reproduction; in particular, they lay eggs instead of giving birth to live young. The platypus—a venomous, egg-laying, duck-billed amphibious mammal—is considered to be one of the strangest creatures in the animal kingdom. When it was first presented by Joseph Banks to English naturalists it was thought to be so strange that it was a cleverly created hoax. The short-beaked echidna is similarly strange, covered in hairy spikes
Steropodon Steropodon Steropodon galmani was a prehistoric species of monotreme, or egg-laying mammal, that lived about 105 million years ago (mya) in the Lower Cretaceous period. It is one of the oldest monotremes discovered, and is one of the oldest Australian mammal discoveries. The dentition of "Steropodon" is somewhat similar to that of therians–the placentals and the marsupials–specifically the presence of the tribosphenic molar tooth which was thought to be exclusive to therians since the Cretaceous. This, along with the tribosphenic molar discoveries of monotreme-relatives "Ausktribosphenos" and "Ambondro" of which the latter evolved in the Jurassic, led to the conclusion that