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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. [1]
Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. Although they are different from almost all mammals in that they lay eggs, like all mammals, the female monotremes nurse their young with milk.
Goat kids will stay with their mother until they are weaned. 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 addition to bony fish and cephalopods, macrolecithal eggs are found in cartilaginous fish, reptiles, birds and monotreme mammals. [3] The eggs of the coelacanths can reach a size of 9 cm (3.5 in) in diameter, and the young go through full development while in the uterus , living on the copious yolk.
Oligophagy is a term for intermediate degrees of selectivity, referring to animals that eat a relatively small range of foods, either because of preference or necessity. [2] Another classification refers to the specific food animals specialize in eating, such as: Carnivore: the eating of animals Araneophagy: eating spiders; Avivore: eating birds
Large mammals develop at an absolute slower rate compared to small mammals. Thus, the large mammal tend have longer gestation periods than small mammal as they tend to produce larger neonate. [22] Large mammals require a longer period of time to attain any proportion of adult mass compared to small mammals. [23]
Among mammals, the monotremes are oviparous. Ovo-viviparity: or oviparity with retention of zygotes in either the female's or in the male's body, but there are no trophic interactions between zygote and parents. [1] This mode is found in the slowworm, Anguis fragilis. In the sea horse, zygotes are retained in the male's ventral "marsupium".
The class Mammalia is divided into two subclasses based on reproductive techniques: monotremes, which lay eggs, and therians, mammals which give live birth, which has two infraclasses: marsupials/metatherians and placentals/eutherians. See List of monotremes and marsupials, and for the clades and families, see Mammal classification ...