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The cleavage stages of marsupial development are very variable between groups and aspects of marsupial early development are not yet fully understood. An infant marsupial is known as a joey . Marsupials have a very short gestation period—usually between 12.5 and 33 days, [ 41 ] but as low as 10.7 days in the case of the stripe-faced dunnart ...
A marsupial has a short gestation period, typically shorter than its estrous cycle, and gives birth to an underdeveloped newborn that then undergoes further development; in many species, this takes place within a pouch-like sac, the marsupium, located in the front of the mother's abdomen.
As a result, there is a double uterus with two separate cervices, and possibly a double vagina as well. Each uterus has a single horn linked to the ipsilateral fallopian tube that faces its ovary. Most non-human mammals have a non-single uterus with separation of horns. Marsupials and rodents have a double uterus (uterus duplex).
The latter subclass is divided into two infraclasses: pouched mammals (metatherians or marsupials), and placental mammals (eutherians, for which see List of placental mammals). Classification updated from Wilson and Reeder's "Mammal Species of the World: A Taxonomic and Geographic Reference" using the "Planet Mammifères" website.
In marsupials, the uterus forms as a duplex organ of two uteri. In monotremes such as the platypus , the uterus is duplex and rather than nurturing the embryo, secretes the shell around the egg. It is essentially identical with the shell gland of birds and reptiles, with which the uterus is homologous .
Another difference is that during the development of embryonic genitourinary tract, in case of female embryo of placental and marsupial mammals, the uterus is formed, a structure that neither monotremata nor lower chordates have. In every case, including monotremata embryos, the milk glands also develop. [4]
The pouch is a distinguishing feature of female marsupials, monotremes [1] [2] [3] (and rarely in the males as in the yapok [4] and the extinct thylacine); the name marsupial is derived from the Latin marsupium, meaning "pouch". This is due to the occurrence of epipubic bones, a pair of bones projecting forward from the pelvis.
As marsupials, female opossums have a reproductive system that includes a bifurcated vagina and a divided uterus; many have a marsupium, the pouch. [29] The average estrous cycle of the Virginia opossum is about 28 days. [30]