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Fossil range: Mid Jurassic-Recent, Template:Fossilrange
A cat (Felis catus) with her kittens
A cat (Felis catus) with her kittens
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Parker & Haswell, 1897 [1]

Theria (File:Loudspeaker.svg /ˈθɪəriə/; Greek: θηρίον, wild beast) is a subclass of mammals[2] that give birth to live young without using a shelled egg, including both eutherians (placental mammals) and metatherians (marsupials and their ancestors). The only omitted extant mammal group is the egg-laying monotremes.

File:Kangaroo and joey03.jpg

Kangaroo, a marsupial, with her joey


Main article: Mammal classification

The rank of 'Theria' may vary depending on the classification system used. The textbook classification system by Vaughan et al. (2000)[3] gives the following:

Class Mammalia

  • Subclass Theria: live-bearing mammals
    • Infraclass Metatheria: marsupials
    • Infraclass Eutheria: placentals

In the above system Theria is a subclass. Alternatively, in the system proposed by McKenna and Bell (1997)[4] it is ranked as a supercohort under the subclass Theriiformes:

Class Mammalia

  • Subclass Theriiformes: live-bearing mammals and their prehistoric relatives
    • Infraclass Holotheria: modern live-bearing mammals and their prehistoric relatives
      • Legion Cladotheria
        • Sublegion Zatheria
          • Infralegion Tribosphenida
            • Supercohort Theria: therian mammals
              • Cohort Marsupialia: marsupials
              • Cohort Placentalia: placentals

Another classification proposed by Luo et al. (2002)[5] does not assign any rank to the taxonomic levels, but uses a purely cladistic system instead.


  1. ITIS Standard Report Page: Theria
  2. Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. Subclass Theria. Animal Diversity Web.
  3. Vaughan, Terry A., James M. Ryan, and Nicholas J. Czaplewski. 2000. Mammalogy: Fourth Edition. Saunders College Publishing, 565 pp. ISBN 0-03-025034-X
  4. McKenna, Malcolm C., and Bell, Susan K. 1997. Classification of Mammals Above the Species Level. Columbia University Press, New York, 631 pp. ISBN 0-231-11013-8
  5. Luo, Z.-X., Z. Kielan-Jaworowska, and R. L. Cifelli. 2002. In quest for a phylogeny of Mesozoic mammals. Acta Palaeontologica Polonica, 47:1-78.

See also

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