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During the course of evolution, the monotremes have lost the gastric glands normally found in mammalian stomachs as an adaptation to their diet. [37] As such, by some definitions, they do not have stomachs as an organ, [38] although the term is widely used in studies of monotreme anatomy. [39] [40] Monotremes synthesize L-ascorbic acid only in ...
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 differ from other mammals because they lay eggs instead of giving birth. There are only five species of monotremes, and they include the platypus and four species of echidnas (spiny ...
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 ...
Echidnas and platypuses are the only egg-laying mammals, the monotremes. The average lifespan of an echidna in the wild is estimated at 14–16 years. Fully grown females can weigh about 4.5 kilograms (9.9 lb), the males 33% larger, at about 6 kilograms (13 lb). [12]
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 ...
The monotremes, including the semi-aquatic platypus and the terrestrial echidnas, are one of the only groups of mammals that have evolved electroreception. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves.
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).