The word 'monotreme' refers to their common rear opening, the cloaca.In amphibia, reptiles, birds and probably all early tetrapods, there is a common opening for urine, reproduction and faeces. File:Long-beakedEchidna.jpg. Would you like to make it the primary and merge this question into it? They produce milk for their offspring from mammary glands through holes in their skin. Platypus definition is - a small carnivorous aquatic monotreme mammal (Ornithorhynchus anatinus) of eastern Australia and Tasmania that has a fleshy bill resembling that of a duck, dense fur, webbed feet, and a broad flattened tail —called also duck-billed platypus. Define monotreme. That is dark billed flat-footed platypus and spiny anteater called echidnas. Fossil discovery and analysis show a slow form of evolution in monotremes compared to other mammals. As well as the platypus, there is the long-beaked echidna and the short-beaked echidna. Monotremes are a group of mammals that form the order Monotremata. Sensitive electroreceptors are located in the skin of the platypus… There are only five living monotreme species: the duck-billed platypus and four species of echidna (also known as spiny anteaters). The monotremes are a group of highly specialised egg-laying predatory mammals, containing the platypus and echidnas. Monotreme definition is - any of an order (Monotremata) of egg-laying mammals comprising the platypuses and echidnas. Monotremes are the only mammals known to possess electroreception, a sense that enables them to locate prey by the electric fields generated by its muscle contraction. Monotremes are not a very diverse group today, and there has not been much fossil information known until rather recently. Monotremes are divided into two broad categories. The sexes avoid each other except to mate, and they do not mate until they are at least four years old. The platypus is a monotreme, not a marsupial and there are just 2 species of monotreme mammals. Monotremes are the only mammals that lay eggs, but they also feed their babies with milk.. After feeding, it retires to its burrow, the entrance of which is large enough to admit only the platypus and serves to squeeze excess moisture from the fur. Some reptile venom is also composed of different types of b-defensins, another trait shared with reptiles. This venom is derived from b-defensins, proteins that are present in mammals that create holes in viral and bacterial pathogens. Platypus - Platypus - Life cycle and reproduction: Despite their abundance, little is known about the life cycle of the platypus in the wild, and few of them have been kept successfully in captivity. It is one of only two mammals (the echidna is the other) that lay eggs. Echidnas lay a single egg in a temporary protective pouch on the mother's belly. Believed to originate some 200 million years ago, these furry mammals retain certain reptilian skeletal features. They look like they were put together by a committee: a bill like a duck, a tail like a beaver, webbed feet, and a furry body. The five extant monotremes -- the duck-billed platypus (Ornithorynchus anatinus) and four species of echidnas (Tachyglossidae) -- live in New Guinea and Australia. Females seal themselves inside one of the burrow's chambers to lay their eggs. The platypus is a monotreme mammal. Monotreme, (order Monotremata), any member of the egg-laying mammalian order Monotremata, which includes the amphibious platypus (family Ornithorhynchidae) and the terrestrial echidnas (family Tachyglossidae) of continental Australia, the Australian island state of Tasmania, and the island of New