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  2. Monotreme - Wikipedia

    en.wikipedia.org/wiki/Monotreme

    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 ...

  3. List of monotremes and marsupials - Wikipedia

    en.wikipedia.org/wiki/List_of_monotremes_and...

    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 ...

  4. Mammalian reproduction - Wikipedia

    en.wikipedia.org/wiki/Mammalian_reproduction

    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 mammal.

  5. File:Monotreme Egg Diagram.svg - Wikipedia

    en.wikipedia.org/wiki/File:Monotreme_Egg_Diagram.svg

    English: Monotremes are oviparous which means that they produce eggs with a lot of (2) yolk inside of the (3) yolk sac so that most of the embryonic development can take place outside of the female reproductive tract. Within the uterus of the female momotreme a (1) double layer shell is secreted around the (5) embryo.

  6. Egg - Wikipedia

    en.wikipedia.org/wiki/Egg

    Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective shell, either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches, i.e., breaks out of the egg's shell.

  7. Oviparity - Wikipedia

    en.wikipedia.org/wiki/Oviparity

    The egg is not retained in the body for most of the period of development of the embryo within the egg, which is the main distinction between oviparity and ovoviviparity. [1] Oviparity occurs in all birds, most reptiles, some fishes, and most arthropods. Among mammals, monotremes (four species of echidna, and the platypus) are uniquely oviparous.

  8. Category:Monotremes - Wikipedia

    en.wikipedia.org/wiki/Category:Monotremes

    This category contains articles about all taxa below the subclass/order Monotremata - the platypus, the echidnas, and extinct species which are only known via fossil evidence. Subcategories This category has the following 5 subcategories, out of 5 total.

  9. Mammal - Wikipedia

    en.wikipedia.org/wiki/Mammal

    However, the five species of monotreme, the platypus and the four species of echidna, lay eggs. The monotremes have a sex-determination system different from that of most other mammals. [131] In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian mammal. [132]