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
Repenomamus and monotremes. Repenomamus Repenomamus is a gobiconodontid mammal genus containing two species, Repenomamus robustus and Repenomamus giganticus. Both species are known from fossils found in China that date to the early Cretaceous period, about 125-123.2 million years ago. "R. robustus" is one of several Mesozoic mammals for which there is good evidence that it fed on vertebrates, including dinosaurs, though it is not possible to determine if it actively hunted live dinosaurs or scavenged dead ones. "R. giganticus" is among the largest mammals known from the Mesozoic era. The fossils were recovered from the lagerstätte of the Yixian Formation in