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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 ...
Monotremes, only five species of which exist, all from Australia and New Guinea, are mammals that lay eggs. They have one opening for excretion and reproduction called the cloaca . They hold the eggs internally for several weeks, providing nutrients, and then lay them and cover them like birds .
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 ...
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.
Hatching takes place after 10 days of gestation; the young echidna, called a puggle, [23] [24] born larval and fetus-like, then sucks milk from the pores of the two milk patches (monotremes have no teats) and remains in the pouch for 45 to 55 days, [25] at which time it starts to develop spines. The mother digs a nursery burrow and deposits the ...
Australia is home to two of the five extant species of monotremes and the majority of the world's marsupials (the remainder are from Papua New Guinea, eastern Indonesia and the Americas). The taxonomy is somewhat fluid; this list generally follows Menkhorst and Knight [ 1 ] and Van Dyck and Strahan, [ 2 ] with some input from the global list ...
The monotremes (short beaked echidna, long beaked echidna, platypus) are testicond seasonal breeding mammals that exhibit some characteristics of the reproductive tract found in reptiles (e.g. testicond, presence of a cloaca). [15] The fully developed monotreme epididymis exhibits two anatomical regions, [2] similar to some reptiles.
In discoidal cleavage, the cleavage furrows do not penetrate the yolk. The embryo forms a disc of cells, called a blasto-disc, on top of the yolk. Discoidal cleavage is commonly found in monotremes, birds, reptiles, and fish that have telolecithal egg cells (egg cells with the yolk concentrated at one end). The layer of cells that have ...