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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 ...
Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia.They are natively found in Australasia, Wallacea, and the Americas.One of the defining features of marsupials is their unique reproductive strategy, where the young are born in a relatively undeveloped state and then nurtured within a pouch on their mother's abdomen.
Kangaroo joey inside the pouch Female eastern grey kangaroo with mature joey in pouch. The pouch is a distinguishing feature of female marsupials and monotremes, [1] [2] [3] and rarely in males as well, such as in the yapok [4] and the extinct thylacine. The name marsupial is derived from the Latin marsupium, meaning "pouch".
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The second subclass is divided into two infraclasses: pouched mammals (the marsupials) and placental mammals. 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 mandibular fossils, MACN 2464 and 3515 were known to be from the water opossum because their teeth were nearly indistinguishable from living populations of the organism in present day. Additionally, water opossum teeth are characteristically different from other didelphids, likely because they are the only semi-aquatic marsupials, making ...
As marsupials, female opossums have a reproductive system that includes a bifurcated vagina and a divided uterus; many have a pouch. [29] The average estrous cycle of the Virginia opossum is about 28 days. [30] Opossums do possess a placenta, [31] but it is short-lived, simple in structure, and, unlike that of placental mammals, not fully ...