Prototheria
| Prototheria Temporal range: Late Triassic - Recent |
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| Short-beaked Echidna | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Subclass: |
Prototheria Gill, 1872 |
| Orders | |
Prototheria (/ˌproʊtəˈθɪəriə, -toʊ-/; from Greek πρώτος, prōtos, first, + θήρ, thēr, wild animal) is a taxonomic group, or taxon, to which the order Monotremata belongs. It was traditionally ranked as a subclass within the mammals; see Yinotheria § History of classification. Modern systems of classification do not recognize this taxon.
Most of the animals in this group are extinct. The egg-laying monotremes are known from fossils of the Cretaceous and Cenozoic periods; they are represented today by the platypus and several species of echidna.
The names Prototheria, Metatheria and Eutheria (meaning "first beasts", "changed beasts", and "true beasts", respectively) refer to the three mammalian groupings of which we have living representatives. Each of the three may be defined as a total clade containing a living crown-group (respectively the Monotremata, Marsupialia and Placentalia) plus any fossil species which are more closely related to that crown-group than to any other living animals.
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