Australosphenida (includes Monotremes: Echidnas and Platypuses)
This infraclass includes a number of extinct orders, as well as the sole recent order Monotremata (i.e. echidnas and the platypus).
Order: Monotremata
Superfamily: Ornithorhynchoidea1
Family: Ornithorhynchidae (platypuses)
—No subordinate taxa
Family: Tachyglossidae (echidnas)
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Megalibgwilia owenii | Krefft, 1868 | Owen's echidna | Late Pleistocene | Australia | Extinct | Access |
| Megalibgwilia ramsayi | Owen, 1884 | Ramsay's echidna | c.48,000 BC | New South Wales & Tasmania, Australia | Invalid (synonym) | Access |
| Murrayglossus hacketti | (Glauert, 1914) | Hackett's giant echidna | c. 38,000 BC? | Western Australia, Australia | Extinct | Access |
| Zaglossus attenboroughi | Flannery & Groves, 1998 | Attenborough's echidna, Cyclops long-beaked echidna, Sir David's long-beaked echidna | (rediscovered) | Cyclops Mountains, New Guinea | Rediscovered | Access |
1 Flannery, Timothy F., McCurry, Matthew R., Rich, Thomas H., Vickers-Rich, Patricia, Smith, Elizabeth T. and Helgen, Kristofer M. (2024). A diverse assemblage of monotremes (Monotremata) from the Cenomanian Lightning Ridge fauna of New South Wales, Australia. Alcheringa: An Australasian Journal of Palaeontology. https://doi.org/10.1080/03115518.2024.2348753