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
Mammal classification through the new concept of cladistics. Though field work gradually made Simpson's classification outdated, it remained the closest thing to an official classification of mammals. See list of placental mammals and list of monotremes and marsupials for more detailed information on mammal genera and species. Molecular studies by molecular systematists, based on DNA analysis, in the early 21st century have revealed new relationships among mammal families. Classification systems based on molecular studies reveal three major groups or lineages of placental mammals- Afrotheria, Xenarthra, and Boreotheria- which diverged from early common ancestors in the Cretaceous. The relationships between these three lineages