The monotremes of Home-Earth form a small group of Australasian oddballs, a trio of species (the platypus and two echidnas) that are unique among living mammals in their retention of many primitive features, the most famous of which is reproduction though egg-laying. They are popularly, if somewhat erroneously, portrayed as “living-fossils”, curiosities from some bygone era that have only survived by living in some biogeographical backwater where “time stood still”.