Monotreme

†Kollikodontidae
Ornithorhynchidae
Tachyglossidae
†Steropodontidae

Monotremes (monos, single + trema, hole; refers to the cloaca) are mammals that lay eggs instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). The subclass comprises a single order, Monotremata (though sometimes the subclass Prototheria is used). An infant monotreme is known as a puggle. Monotremes are the only mammals known to be capable of electroreception.