article: Monotreme
links: Eutheria Upper Triassic Sir David's Long-beaked Echidna Lower Cretaceous Animal Western Long-beaked Echidna Chordate Kollikodontidae Short-beaked Echidna Australia Echidna Australosphenida Ornithorhynchidae New South Wales Tachyglossidae Mammal Eastern Long-beaked Echidna Steropodontidae Short-beaked echidna Upper Cretaceous Metatheria Platypus Egg (biology) New Guinea