Search results
Results from the WOW.Com Content Network
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 ...
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 ...
Mammals are divided into two subclasses based on reproductive techniques: egg laying mammals (the monotremes), and live birth mammals. The second subclass is divided into two infraclasses: pouched mammals (the marsupials) and placental mammals.
The divergence between oviparous (egg-laying) and viviparous (offspring develop internally) mammals is believed to date to the Triassic period. [31] Most findings from genetics studies (especially of nuclear genes) are in agreement with the paleontological dating, but some other evidence, like mitochondrial DNA, give slightly different dates. [32]
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 ...
The egg-laying mammal, named after broadcaster Sir David Attenborough, was last seen by scientists in 1961. ... “The reason it appears so unlike other mammals is because it is a member of the ...
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.
An expedition through an unpredictable, perilous mountain range in Indonesia’s province of Papua led to the rediscovery of a critically endangered egg-laying mammal that hasn’t been seen for ...