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Monotremes (/ ˈ m ɒ n ə t r iː m z /) are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tract ...
The class Mammalia is divided into two subclasses based on reproductive techniques: egg-laying mammals (yinotherians or monotremes - see also Australosphenida), and mammals which give live birth . The latter subclass is divided into two infraclasses: pouched mammals ( metatherians or marsupials ), and placental mammals ( eutherians , for which ...
The four extant species of echidnas and the platypus are the only living mammals that lay eggs and the only surviving members of the order Monotremata. [3] The diet of some species consists of ants and termites, but they are not closely related to the American true anteaters or to hedgehogs. Their young are called puggles.
Most mammals are viviparous, giving birth to live young. [1] However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. [2] In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian ...
Monotremes are the only mammals (apart from the Guiana dolphin) [50] known to have a sense of electroreception, and the platypus's electroreception is the most sensitive of any monotreme. [ 51 ] [ 49 ] Feeding by neither sight nor smell, [ 52 ] the platypus closes its eyes, ears, and nose when it dives. [ 53 ]
These Australian mammals are part of a mostly-extinct group of mammals known as monotremes that have some un-mammalish habits. For example, laying eggs! However, like other good mammal mothers ...
Much of the argument is based on monotremes (egg-laying mammals): [120] [121] [122] While the amniote egg is usually described as able to evolve away from water, most reptile eggs actually need moisture if they are not to dry out. Monotremes do not have nipples, but secrete milk from a hairy patch on their bellies.
Oviparity: fertilisation is internal, but the female lays zygotes as eggs with a substantial quantity of yolk to feed the embryo while it remains in the egg. The egg is not retained in the body, or only for a limited time. [1] Oviparity is found in insects, birds. Among mammals, the monotremes are oviparous.