Prototheria

The Prototheria is a former subclass of mammals, now no longer in use. The name comes from Greek prōtos means 'first', and thēr, 'beast'. The only surviving animals in this subclass are the Monotremes.

Prototheria Temporal range: Upper Triassic – Recent
Short-beaked Echidna
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Subclass:	Prototheria Gill, 1872
Orders
†Morganucodonta †Triconodonta †Docodonta †Multituberculata Monotremata

There are two other subclasses, the Metatheria and the Eutheria. Metatheria contains the marsupials. All the other mammals are Eutherian.

Evidence is accumulating that the Prototheria is not a natural group, but alternative suggestions are not yet agreed.^[1][2] The term is not listed in Benton's 4th edition (2015), so it is now a dead term.