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.

Therians Fossil range: Early Cretaceous-Recent, 125–0 Ma PreЄ Є O S D C P T J K Pg N
A cat (Felis catus) with her kittens
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	Theriiformes
Superorder:	Theria Parker & Haswell, 1897
Infraclasses
Eutheria Metatheria †Trituberculata

This article appears to contradict the article Eutheria. Please see discussion on the linked talk page. Please do not remove this message until the contradictions are resolved. (October 2009)

Theria (pronounced /ˈθɪərɪə/, 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).

Kangaroo, a marsupial, with her joey

Extent

Members of this subclass 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 known 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. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Theria.html. 

v • d • e Extant mammal orders by infraclass Kingdom Animalia · Phylum Chordata · Subphylum Vertebrata · (unranked) Amniota Australosphenida Monotremata (Platypus and echidnas) Metatheria (Marsupial inclusive) Didelphimorphia (Opossums) · Paucituberculata (Shrew opossums) · Microbiotheria (Monito del Monte) · Notoryctemorphia (Marsupial moles) · Dasyuromorphia (Quolls and dunnarts) · Peramelemorphia (Bilbies and bandicoots) · Diprotodontia (Kangaroos and relatives) Eutheria Afrosoricida (Tenrecs and golden moles) · Macroscelidea (Elephant shrews) · Tubulidentata (Aardvark) · Hyracoidea (Hyraxes) · Proboscidea (Elephants) · Sirenia (Dugongs and manatees) · Cingulata (Armadillos) · Pilosa (Anteaters and sloths) · Scandentia (Treeshrews) · Dermoptera (Colugos) · Primates · Rodentia (Rodents) · Lagomorpha (Rabbits and relatives) · Erinaceomorpha (Hedgehogs and relatives) · Soricomorpha (Shrews and moles) · Chiroptera (Bats) · Pholidota (Pangolins) · Carnivora · Perissodactyla (Odd-toed ungulates) · Artiodactyla (Even-toed ungulates) · Cetacea (Whales and dolphins)

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