Theria

(vertebrate zoology) A subclass of the class Mammalia including all living mammals except the monotremes.

One of the four subclasses of the class Mammalia, including all living mammals except the monotremes. The Theria were by far the most successful of the several mammalian stocks that arose from the mammallike reptiles in the Triassic. The subclass is divided into three infraclasses: Pantotheria (no living survivors), Metatheria (marsupials), and Eutheria (placentals). Therian mammals are characterized by the distinctive structural history of the molar teeth. The fossil record shows that all the extremely varied therian molar types were derived from a common tribosphenic type in which three main cusps, arranged in a triangle on the upper molar, are opposed to a reversed triangle and basinlike heel on the lower molar. See also Mammalia; Therapsida.

Therian Fossil range: Middle Cretaceous - Recent
House Mouse, Mus musculus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Subclass: Theria Parker & Haswell, 1897
Infraclasses
Metatheria Eutheria

Red-necked Wallaby

This article is about one particular subclass of mammals. If you are intending to use the word "therian" as a synonym for "therianthrope", used predominantly in the context of modern subcultures, see "Therianthropy (subculture)".

Theria (pronounced from the Greek θηρίον, wild beast) is a subclass of mammals^[1] that give birth to live young without using a shelled egg, including both eutherians (placental mammals) and metatherians (marsupials and their ancestors). They have external ears, most can suckle on a nipple, and have an ankle specialized for power and range of motion. Therians are often classified by their specialized dentition. Almost all currently extant (not extinct) mammals are therians. The only exceptions are the platypus and the echidnas (spiny anteater), both of which are prototherian monotremes.

Bibliography

• Vaughan, Terry A., James M. Ryan, and Nicholas J. Czaplewski. 2000. Mammalogy: Fourth Edition. Saunders College Publishing, 565 pp. ISBN 0-03-025034-X

References

1. ^ Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. Subclass Theria. Animal Diversity Web.

External links

lij:Theria

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